w SUPPLEMETI MATERML. 0! TE! 31.7 m L m1?- Robert mg, a 31 [I mica m: the land: Test 8‘. a: 7119-! | depth of I :3 stated, wally Val-it mm “123, densely «1:1! 331mm: cuter ha Inalnaf 1.7 x 135 I}. 341911;: block: fro- the “ME! Rider! tuft. 3.33135 ‘51 eiem. con: 3km, what! ft 3m h" ‘3‘ "mated ABSTRACT THE EFFECT OF THE GEOLOGIC SETTING ON THE DISTRIBUTION OF EJECTA PROHIA BURIED NUCLEAR.DETONATION BY Robert warren Benny schooner, a 31 KT nuclear excavation experiment, was detonated at the Revada Test Site in a horizontally layered ruff sequence. The 108 e.depth of burst was slightly below a 65 m thick, nearly saturated, weakly welded tuff layer which was sandwiched between two dry, densely welded tuff layers. The apparent crater has a radius of 130 n, a depth of 63 m, and a volume of 1.7 x 105 .9. Edecta are strongly bimodal with boulder-size blocks free the densely welded tuff and sand-size fines free the weakly welded tuff. The continuous ejecta field contains over 902 of the ejects, concentrated in eleven rays distributed nonsyl-etrically outward froe the crater to an average distance of 510 I. Rays are separated by valleys which contain little ejects. The continuous ejects field exhibits an inverted stratigraphic order with lower-oat in situ units concentrated towards ray axes and the crater til. Rays are overlain by mixed fines which flowed, smoothing over and partially eroding underlying deposits. The discontinuous ejects field also exhibits an inverted stratigraphic order to its naxinun range of 2150 1. Unlike in the continuous, ejects tend to be concentrated radially outward fro-.valleys. The logical sequence of observed events and the detailed stratigraphic ordering of the ejects field suggests that foreationsl was: ordered. Such F 3:31;: setting. “it! fit? up: melanin phase ml? iispersed eject: fie' assure: nfot joint 1. 2:11;; mi inflation the “-50 PhYSiCIl propertie “‘39 ad ttmcture of the 1:15:33” of the c1 3" mutation of the 115:3. Hm, I: an m! six men through 6.1: .1 it." e but: fr“ “515:: wise for Other 8601031: Robert Warren Henny processes were ordered. Such processes were strongly affected by the geologic setting. Water content was most important, fueling a nassive gas acceleration phase which produced the large crater and the widely dispersed ejects field. Other controlling geologic paraseters were: najor joint trends (orientation of major rays), joint spacing and foliation characteristics (ejects block size and shape), bulk physical properties (bimodal ej ecta characteristics and lorphology and structure of the ejects field), and surface gradient (downhill enlarge-eat of the crater and discontinuous ej ecta field). The application of the Schooner results to cratering analyses is twofold. First, as an analog to aid in the interpretation of existing craters through direct comparison of similar features. And Second, as a basis from which to hypothesize crater and ej ecta processes for other geologic and source environments. M’ n l .u—4._ milu.“ TEEEF?ECT 0! OS “'2 32‘" at. .J. F1111 5:315: fisher Mich: . 1‘ ”Rial 5:112: ‘THE EFFECT OF THE GEOLOGIC SETTING ON THE DISTRIBUTION OF EJECTA FROM A BURIED NUCLEAR DETONATION 3? Robert warren Benny A.DISSERTATION Submitted to Hflchigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Geology 1977 Indexed to Dr. 9111‘. 3:23:36 present‘. at Purl 2-5.. niece, and {ethnic 393‘.- Ieppteciue t': ‘47; blunt, Katina S V'- '-.‘£’.‘.:nlnly than}. 1 "'3 '1 ”he: canittee m n: 1"” 3°". for I “m Roddy (rs-:53; CFR' '33" 50th "9cm n - le’. ACKNOWLEDGMENTS I am indebted to Dr. William Hinze, formally of Michigan State University and presently at Purdue University, for his continued interest, patience, and technical guidance throughout the long course of this study. I appreciate the every assistance given by the Geology Department, Michigan State University, during the past several years. I particularly thank.my committee chairman, Dr. William Cambray, and other co-Iittee members, Drs. Hugh Bennett, Russell Harmon, and James Trow, for their considered guidance. Dr. Dave Roddy (USGS/I'lagstaff) and Dr. Henry Moore (uscs/ Henlo Park) have both spent much time with me over the past several years discussing various aspects of the Schooner crater and ejecta field, both in correspondence and at the Schooner site. I am grateful for their meaningful and valued comments. I am obliged to several organizations for financial support. During my residency at Michigan State University I received financial assistance from.a NASA Research Fellowship. The considerable expense involved in conducting the necessary field work, both before and after the Schooner detonation.was borne by the Defense Nuclear Agency and the United States Air Force, Space and Missile Organization. In addition, the former provided much of the drafting and photographic support necessary in producing this document. Most of all, my employer, the Civil Engineering Research Division, Air Force weapons ii mum“. 5" Ker". an}: ad claim sup-t. a: mien this study. F3151 um I} wtie, r. 3:: 1'11: we: eating u :1 as hard“ yem. Laboratory, Albuquerque, New Mexico, has been a continued source of both financial and clerical support without which I would have been unable to complete this study. Finally, I thank my wife, Marilyn, and children, Kirsten and Robert, for their never ending understanding and encouragement during those "hard" years. iii I KEYED. L Statement of the ': 1. Previous Research 1. Terrestrial I 1. laboratory Cr 3. Hizh-Extlcsiu -- The Schooner Eve 3- than to the .‘W' " a '- $27.13, L EraNiogtap'm r " Structure '3. 3' ‘ "Sit—ll Pro-Pa. 353: 5“ C‘MTEI‘; A. : 14“” Procease 1' “musing i' EjfiCtlon ‘. km‘itim ' 3e .. 5- (‘1 Su“ "M For II. III. TABLE OF CONTENTS INTRODUCTION A. Statement of the Problem B. Previous Research 1. Terrestrial Impact Structures 2. Laboratory Cratering Experiments 3. High-Explosive and Nuclear Field Tests C. The Schooner Event D. Approach to the Problem GEOLOGIC SETTING A. Physiography B. Stratigraphy C. Structure D. Physical Properties TRANSIENT CRATERING PEENOMENA A, Major Processes l . Rounding 2. Ejection 3. Deposition 4. Base Surge Formation 5. Cloud Formation B. Edecta Impacts 1. Mapping Procedures 2. Distribution of Impacts 3. Time Sequence of Impacts iv Page UIJ-‘U N \l 13 23 26 28 28 28 32 34 35 35 37 37 38 39 ZE‘EI'JSAL CFJSJL'TE'? l0 £5333 FIELD 1. Definition of Va: 1. Crater 2. Lin !. Dismissal Eels: 1' ”Pitts: Crat 1- Ware-at 1.1; L Crests 5- Tweets c. 33.. d- Valleys 1' 53.3.31! 23: C} 2' A;?drent L. “1mm: Rel bpdfut ‘L Y'Vallc‘ ‘hylw Dara: Prat 1. , SIIE‘CQ ] a. the: b. Soda C. will :1. 7‘11 to r: IV. TABLE OF CONTENTS (cont'd) DIMENSIONAL CHARACTERISTICS OF THE CRATER A. AND EJECTA FIELD Definition of Major Features 1. Crater 2. Lip Dimensional Relationships 1. Apparent Crater 2. Apparent Lip a. Crests b. Troughs c. Rays d. Valleys Areal Relationships 1. Apparent Crater 2. Apparent Lip Volumetric Relationships 1. Apparent Lip 2. Ray-Valley Comparisons 3. Ray 1 Variations 4. Cumulative Distributions GEOMORPHIC CHARACTERISTICS OF THE CRATER AND A. B. CONTINUOUS EJECTA FIELD General Apparent Crater 1. Surface Morphology a. Overturned Ejecta Flap b. Soil Horizon c. wa11 d. Fallback e. Floor 47 47 54 56 58 58 60 61 63 64 65 65 69 7O 70 72 75 77 8O 8O 84 84 86 85 85 85 87 1.1.32.3 OF; 2. Elect Site 3. Black Areal .: C. Continuous Zjecta 1. Surface Herr. a. Bloch] Ar 1). Rubble Ar t. Sloct'a A: 2. Block Size 3. Block Ar“: 1 “9. P~' l " ”on. o - "u I C ‘ . . ' \ .* ‘ I .h-\‘ n C-KISIIS 2:312 L {“1033 Of the l 3- 'I'all " Strati; b. Strutt; c. Crate: Eject. 313 F‘ Strata TABLE OF CONTENTS 2. Block Size 3. Block Areal Density Continuous Ejects Field 1. Surface Morphology a. Blocky Areas b. Rubble Areas c. Smooth Areas 2. Block Size 3. Block Areal Density (cont'd) VI. GEOLOGIC CHARACTERISTICS OF THE CRATER AND A. CONTINUOUS EJECTA FIELD Geology of the Crater Lip 1. Overview 2. Mapping Procedures 3. wa11 a. Stratigraphy b. Structure c. Cratering Effects 4. Ejecta Flap a. Stratigraphy b. Structure 5. Soil Horizon Geology of the Trench 1. Physical Setting 2. Mapping Procedures 3. Major Features 4. Block Units a. Primary Features b. Secondary Features c. Tertiary Features vi 89 90 92 94 96 98 100 100 100 101 102 102 109 111 112 112 121 123 124 124 125 125 133 I33 135 136 ). pm 3:"). 3. Um“ : - I 5- 5&33'133‘ c, 36:11.?" 5. m:- =' I. 511221? b. hoteratel ea '3 ' to It“ “'1“ . S|-': - a ‘. u h-aane JE‘SZ? 1. Physiza'. 561 2. Rania“ 3"? ;v\ 3. C011: 1233's.: E a. Block 1': b. Fine 1": c. H11 331 . Falls-.9. A k. .rater I‘fi ‘2‘“? ..... .......JX 3? if" N'I‘V". ‘ bi‘fieus 5” Overview 0 General 31 str‘ 1. 3 Blocks ~ Seceadaw \l .. «3.3.1:? Pr 3 5 r a f“ r' L: N " m 0 a; I? r. ‘L '. .I a a." a"... O VII. TABLE OF CONTENTS (cont'd) 5. Fine Units a. Primary Features b. Secondary Features c. Tertiary Features 6. Mix Units a. Slightly Mixed (A?) b. Moderately Mixed Ax) c. well Mixed (X) C. Surface Geology 1. Physical Setting 2. Mapping Procedures 3. Continuous Ejecta Field a. Block Units b. Fine Units c. Mix Units d. Fallout Unit 4. Crater DISTRIBUTION OF EJECTA BLOCKS AND SECONDARY CRATERS A. Overview B. General Distribution 1. Mapping Procedures 2. Blocks 3. Secondary Craters C. Detailed Distributions Along Ray 1 and Valley 11 Radials 1. Mapping Procedures 2. Blocks a. Fused-Glass Encssed Blocks b. Stratigraphy c. Size d. Shape e. Volume vii 169 175 175 177 181 183 183 185 185 189 192 195 196 masses 3mm; 1. an at ' sec-lame- I. Seconiarjc Cr 3. a. Frequent? b. Size c. S d. Stratirra D e. 3 CF"?! .15: L“! Sthooaer 33:23:, 1. Scaled Crs: 3‘ 555' 5313:): 5- Distributic Relaticmships " 35th: 1" Aftsr OJ ' Surflce 1: 1. Area b‘ Lbca‘. Co $011 w ' Litho‘. . TABLE OF CONTENTS (cont'd) Secondary Craters a. Frequency and Volume b. Size c. Shape d. Stratigraphy VIII. RELATIONSHIPS BETWEEN THE GEOLOGIC SETTING AND THE CRATER AND EJECTA FIELD A. B. Schooner Compared 1. 2. 3. 4. Crater Shape Scaled Crater Dimensions Mass Balance Distribution of Ejecta Mass Relationships 1. 2. 3. weather a. During the Event b. After the Event Surface Terrain a. Area Gradient b. Local Topography c. Soil Cover Lithologic Characteristics a. Bulk Properties b. Specific Properties Layering Joint Trends a. Ray-Valley Structure of the Apparent Lip b. Ejects Impacts c. Blocks in the Discontinuous Ejecta Field Joint Spacing and Foliation Characteristics viii 202 202 205 207 207 207 211 211 213 214 214 218 218 219 219 224 226 227 227 230 233 233 TABLE 3? t ' "7 3153333 3? 218.1"? L. ieneral Seance 3. 'Jetailad Sequence: 1. E‘s-:35 in: ?‘r.a . 1. Ejetttcc Pie 3. Deposition P' 1 37.531353 1- Orierl Y PYOCtSSa I. Iagortant (veclo: «mutation 5‘ 933A TABLE OF CONTENTS (cont'd) TIME HISTORY OF CRATER AND EJECTA PROCESSES A. General Sequence B. Detailed Sequence 1. Mounding Phase (0 to 1.75 sec) 2. Ejection Phase (1.75 to ~71 sec) 3. Deposition Phase (4 to ~81 sec) CONCLUSIONS A. Orderly Processes B. Important Geologic Parameters C. Applications APPENDIX A STRATIGRAPHIC AND PHYSICAL PROPERTY DATA FOR THE SCHOONER SITE ‘ APPENDIX B STEREOPHOTOGRAMMETRIC MAPPING, PROFILING, AND VOLUMETRIC COMPUTATIONS APPENDIX C GEOMORPHIC REGIMES, MAPPING PROCEDURES, AND DATA TABULATION: APPENDIX D MASS BALANCE COMPUTATIONS REFERENCES 239 239 242 245 249 249 252 254 B1 Cl D1 IE)". ;, '3‘.qu - Maia ‘Ies '. Him 0‘. Schooner 3. Ltegaphy of Schooner 5- lattice of kploratc: ' “Fresno: of 5mm m Snooze: Site Terence Liver-ore La a “.03th [fiesta him: lap of the S; truism ant Schl- mmez Site Srrehtioa between 5 “my and 23m. ' Site 6. 7. 8. 9. 10. 11. 12. LIST OF FIGURES Indexzflap - Nevada Test Site, Pahute Mesa, and Schooner Site Two Views of Schooner 362 Area (Lawrence Livermore Laboratory Photos) Topography of Schooner Plateau with Average Crater and Continuous Ejecta Boundary Indicated Geologic Map of the Schooner Plateau (After Christiansen and Noble, 1968) Location of Exploratory Drill Holes Near Schooner Site Correlation between Stratigraphic, Mapping, Physical Property, and Edects Units at Schooner Site . Correlation of Stratigraphic Units across Schooner Site Correlation of Mapping Units across Schooner Crater Area Using Continuous Density Logs from Drill Holes UZOu-l, 2. 3, m ‘ Orientation of Joints in the Trail Ridge Member (Mapping Units "R” and "U") of the Thirsty Canyon Toff at Three Locations Surrounding Schooner scz (After Purtymun, et al., 1969) Schooner Detonation Sequence from 0.8 to 13.0 Seconds after Detonation as Observed from Ground-Based High- Speed Cinema located at Azimuth 145° and 5,738 m from.SGz Overhead Views of Schooner 15 and 27 Seconds after Detonation Mound Development and Venting Patterns from 0.5 to 2.3 Seconds after Detonation as Observed from Overhead High-Speed Cinema 12 14 15 18 20 22 25 29 3O 31 he? .__ : 3291" mg: Distrihu “alum fisher of E I. Smhtive Dutrihuti: t—l ,. if 15: 0! M St!!! httlm! I! :a herbal Til! 5*. Sear Interval: u a lie: md Culture Ill Function of his. Skirted Azimuth: as m‘ The 33mm of meta 1. than and The :t. Altitude Aerial “18 and Eject: rte 15. 16. 17. 18. 19 . 20. 21. 22. 23. -24. 25. '26. 27. LIST OF FIGURES (cont'd) Base Surge Patterns as a Function of Time as Observed from Overhead Time Sequencing Photography Ejecta Impact Distributional Patterns Observed from Overhead Time Sequencing Photography Cumulative Number of Ej ecta Impacts at Four- Second Intervals as a Function of Azimuth Number and Cumulative Number of Ejecta Impacts as a Function of Azimth Cumulative Distributions of Ejecta Impacts for Selected Azimuths as a Function of Distance and Time Frequency of Ejecta Impacts as a Function of Distance and Time High Altitude Aerial Photograph of the Schooner Crater and Ejecta Field Intermediate Altitude Aerial Photograph of the Schooner Crater and Ejecta Field Low Altitude Aerial Photograph of the Schooner Crater and Ej ecta Field Aerial Oblique Photographs of the Schooner Crater and E1 ecta Field Averaged Profile of the Schooner Crater and Ej ecta Field (See Key to Symbols and Abbreviations) Modified Isopach Map of Schooner Crater and Ej ecta Blanket with Skewed Ray and Valley Axes Indicated Apparent Dimensions . . . Crater Radius, Lip Radius, and Lip Height as a Function of Azimuth Apparent, True, and Ejecta Lip Heights at Crests and Troughs along the Crater Rim Comparison of Selected Isopach Contours with Their Mean Contours xi 40 42 43 45 46 49 50 51 52 53 59 62 66 hi we ‘r‘ .u‘ ‘<-—- . “'33,.— v—a. ‘L W); n." ' hi- LIST 0? harm Crater, Apps: Thine: for Each c mtmt mo' True Cra'~ 1,3, 7, and 10 late: and Lip Volume“. a filler: scent Crater m L 5.3194 h 00! Degree I‘xrihution of Lip, Ejecta Value for by Faction of Distance 2 Estri‘mtim of Con“ faction of 33113: e at ml,” Gum-pm Enter an Wmhlt CIIIQI u mouse Creole-g; fitomph of , For 361mm 9" . mt ' u'. 514110“ o?" 1,, Crest. r . #1 him napping t. ‘o r 3" Join all y “at v A‘i.‘ *a; OS Hee“. «I 11 “ea' :1 v‘Ze Jr an? “Ti-$4 L4 ‘2‘! ‘all m Q’; re 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. LIST OF FIGURES (cont'd) Apparent Crater, Apparent Lip, and Nermalized Lip Volumes for Each of the Eleven Rays Apparent and True Crater Profiles for Ray Axes. l, 3, 7, and 10 Crater and Lip Volumetric Comparisons for Rays and Valleys Apparent Crater and Lip Volumes for Radials Spaced in One Degree Increments Across Ray 1 Distribution of Lip, Upthrust, and Continuous Ejecta Volume for Ray 9 and Valley 1 as a Function of Distance from SGZ Distribution of Continuous Ejecta Volume as a Function of Distance from SGZ for Selected Rays and Valleys Geomorphic Crater and Eflecta.Map - Surface Features Geomorphic Crater and Ejecta Map - Block Size Geomorphic Crater and Edecta'Msp - Block Areal Density Generalized Geologic Map of the Crater Lip Photograph of a Portion of Crest 9 with Mapping Units Indicated Selected Photographs of the Crater Lip with Lip Stations and Create Indicated In Situ Mapping Unit Thicknesses in the Crater wall Major and Minor Joint Trends for welded Units in the Crater wo11 Trace Map of welded Blocks in the Ejecta Flap and Crater wa11 Beneath Trough 9 Size and Shape Distributions of welded Blocks in the Crater wall - Trough 9 xii 74 76 78 79 81 82 87 103 105 106 108 110 113 114 Figure 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. LIST OF FIGURES (cont'd) Size and Shape Distributions of Welded Blocks in the Ejecta Flap - Trough 9 Ejecta Mapping Unit Thicknesses in the Ejecta Flap Photograph of the Trench Through Crest l with Trench Stations and Mapping Units Indicated Selected Photographs of the Trench with Trench Stations Indicated (Clip Board is 35 cm Long) Selected Photographs of the Trench with Trench Stations Indicated (Clip Board is 35 cm Long) Generalized Geologic Map of the Trench Distribution of Major Ejecta Units along the Trench Geologic Map of the Crater and Continuous Ejecta Field Selected Photographs of the Continuous Ejecta Field Selected Photographs of the Continuous Ejecta Field Selected Photographs of the Continuous Ejecta Field Selected Photographs of the Discontinuous Ejecta Field Selected Photographs of the Discontinuous Ejecta Field Station Locations for Measurements of Ejecta Blocks and Secondary Craters Statistics for Ejecta Block Lengths as a Function of Distance from SGZ with Azimuthsl Variations Indicated Block Volume as a Function of Azimuth at 610 Meters from SGZ Frequency and Cumulative Frequency of Secondary Craters as a Function of Distance from SGZ xiii 126 127 128 129 131 149 151 153 155 171 173 176 178 180 182 5 13:5{by101m of 3 LIST C hm! °f “53$"? Birth Past by 101“ °f E 3111121 u s hoctio?‘ !-1 mi V-ll beings as s Functior liter Circuafersot Lal Fret Mosaics b' Fatim of Distance '. 14.1 hd‘lals with She Lr'icstsd he: Block Volta. u along H and V-l F re 61. 62. 63. 65. 66. 67. 68. 69. 70. 71. 72. LIST OF FIGURES (cont'd) Frequency of Secondary Craters as a Function of Azimuth Percent by Vblume of Blocks with Fused-Glass Coatings as a Function of Distance along Radials R91 and V-ll Percent by Volume of Blocks with Fused-Glass Coatings as a Function of Azimuth along the 1021 Meter Circumferential Stations Percent Cbmposition by Volume of Blocks as a Function of Distance from SGZ along the R91 and V-ll Radials with Skewed Ray and Valley Axes Indicated Percent Composition by Volume of "R" + "U" Blocks as a Function.of Azimuth at the 457, 610, and 1021 Meter Stations with Skewed Ray and Valley Axes Indicated Mean Block.Volume as a Function of Distance from SGZ along R91 and Vrll Radials ‘Mean Block.Volume as a Function of Azimuth at 457, 610, and 1021 Meter Stations with Skewed Ray and Valley Axes Indicated Block Volume as a Function of Distance from SGZ along R91 and V-ll Radials Frequency of Secondary Craters as a Function of Distance from SGZ along R91 and V511 Radials with Skewed Ray and Valley Axes Indicated Frequency of Secondary Craters as a Function of Azimuth along the 1021 Meter Stations Comparison of Apparent and True Crater Shapes from Buried Nuclear Detonations in Rock and Soil Scaled Crater Dimensions for Buried Nuclear Detonations in Rock and Soil xiv 188 190 191 193 194 197 198 200 203 206 'H '- a- ; rental Distrihuti lmlsttou betveen J (‘i '1 fi—s’ LIST 0? afiistmce frm SGZ 5 hm 30! erelstion hetveen A: Fresh: Topogrsphic C. Statue of the Cost inflation hetveen 5' first Ara m. Velocity 1». 5‘2) ' ' 333mm Profiles Wants for Celi 74. 75. 76. BI. 82. B3. D1. D2. LIST OF FIGURES (cont'd) Incruental Distribution of Ejecta as a Function of Distance from.SGZ for Schooner, Sedan, and Danny Boy Correlation between Apparent Crater Radius and Preshot Topographic Gradient Correlation between Joint Trends and the Ray-Valley Structure of the Continuous Ejecta Field Correlation between Ej ecta Impacts and Crest and Trough Axes Downhole Velocity Profile for Ue20u-3 (From Tewes, 1970) Bulk Density Profiles from In Situ and Laboratory Measurements for Ue20u-3 and U20u (From Tewes, 1970) Porosity Profiles from Laboratory Measurements for Ue20u-3 and U20u (From Tewes, 1970) Free Water and Saturation Profiles from Laboratory Measurements for Ue20u-3 and U20u (From Tewes, 1970) Loading and Unloading Pressure-Volume Curves for Four Representative Samples from Ue20u-3 (From Lessler, 1968) Preshot Topographic Map of Schooner SGZ Area Post shot Topographic Map of Schooner Crater and Ej ecta Blanket Isopach Map of Schooner Crater and E] ecta Blanket Sketch Illustrating Mass Balance Relationships Ejecta Areal Density as a Function of Distance from SGZ 216 228 231 A9 A10 A13 A14 A16 82 B3 B4 D2 D6 m ,' km. 33111 Sole T '. Emu basins sees and Shaw 05 ‘ n: Ejecta Fir; a: Ct Eass Palm: Ratios f Itscrip-tion of Fruit. kaimtion of V mical Properties ‘ xmuer Apparent Cr '- mer Crater and '. in 1nd Valley stemWhit Raises Table 1. 2. 3. Bl. B2. C1. D1. LIST OF TABLES Schooner Drill Hole Data Schooner Dimensions Sizes and Shapes of Blocks in the Crater Wall and Ejecta Flap at Crest 9 Mass Balance Ratios for Schooner and Sedan Description of Mapping Units Based on Field Examination of UZOu-Z Core and Ejecta Deposits Physical Properties of Schooner Media Schooner Apparent Crater and Lip Volumes for Each Ray Schooner Crater and Lip Volume Components for Each Ray and Valley Geomorphic Regimes Schooner Volume, Density, and Mass Data xvi 16 57 116 208 A17 B9 B12 CS D3 (m: m 10 1;in hater w} E: Jamil: Enter mi E; .. Quentin Crater and if ‘ Sciatic hp of the Ctr. , £1.11: Hap of the 2:: ~, £1.21ch of the CI: LIST OF MAPS (Maps are located in the map pocket) Geomorphic Crater and Ejecta Map - Surface Features Geomorphic Crater and Ejecta Map - Block Size Geomorphic Crater and Ejecta Map - Block Areal Density Geologic Map of the Crater Lip Geologic Map of the Trench Geologic Map of the Crater and Continuous Ejecta Field xvii . 1 I. 21:55 amen-rise 33:1? Ecidnatims are :e‘ ,3“ ' . . I . 5335-3811.; ,4. an: ‘at‘ 1'. Crest 1 (also ( ' £11121: iggth , | '1 “Hill. d€:t' (see text? 3‘. 53113:: it: :1: v: " D9“ °f b‘Jts‘. : V . .OY-mzfi “0,131.; I Q' .1: Amara: 113 '11 2 ' 33:! {Men '1‘. d” ‘ 4e I‘D cre Jmiles) L-t .. r. mater 11p 8 u ‘ n 38 ¢ FL . h, (on: - I 0 4 I! ‘ dd: v ‘1“ °5 1: . 3* 0»: ‘ I as. Of c L .l «ex 1 KEY TO SYMBOLS AND ABBREVIATIONS Unless otherwise specified, all distances are referenced to SGZ and all elevations are referenced to preshot ground surface. See Figures 23 and D1 and Table 2 for added information on terms. C-l He1 CI‘GSt 1 (8180 C-2, 3, see, 11) Maximum depth of apparent crater Maximum depth of "corrected" apparent crater (see text) Maximum depth of true crater Depth of burst Youngs Modulus . 2 Shape factor (F Va/nRa Da) Apparent lip crest height Edecta thickness at crater crest True lip crest height Yield of explosive in kilotons (1 KI . 4.2 x 1012 Joules) Crater lip station 1 (also L:2, 3, ..., 40) Mass of apparent crater Mass of continuous ejects Mass of discontinuous ejecta Mass of total ejects Mass of fallback Mass of cloud xviii “ r J- L‘ I- ,.:. .r‘ ‘5' r5" .6” .r’ .r' 4" J" F I... U ..4 2.. «2‘1. '1 a” x” 5' ‘4" 1y Kissing crate: less of true C‘ has: of 2:351“: Ease of cm?“ Unarmed as {commhic sat Raiius of ac?! Radius of um him of the Radius of ta: hits: to o-.- hdius of t'.‘ 335133 to at Radius of " Ediius of ‘ KEY TO SYMBOLS AND ABBREVIATIONS (cont'd) E}? 2 “4 Rd 341 Retarc sal Sd' Mussing crater mass Mass of true crater Mass of upthrust Mass of compacted zone Unaccounted'mass Geomorphic mapping area (also M:2, 3, ....,559) Radius of apparent crater Radius of apparent lip crest Radius of the continuous block boundary Radius of cavity below ZP Radius to outer displaced boundary Radius of the continuous ejecta boundary Radius to maximum ejecta range Radius of "R" boundary Radius of true crater Radius of true crater lip Ray 1 (also R-Z, 3, ..., ll) Rubble mound (crater spelled backwards) Apparent crater surface Apparent lip surface Displaced ground surface Original ground surface Preshot ground surface xix -1 {J ' (’0 I s LI. E? To SWELS At Tm crater su'. Cythmst surf a Surfaze gram; Total éett'a of Tmug': 1 (else Trench static: .bparent .. . 5a “' \ p wntinuou; tie DiSCOntiaum; 3°!“ tiecte ~. Fullback '01“, Cloud .01 use Apparent 11p . lush! cute: Capra" ima‘ True crater v “thrust '01” KEY TO SYMBOLS AND ABBREVIATIONS (cont'd) St True crater surface Su Upthrust surface SGZ Surface ground zero T.D. Total depth of a drill hole T-l Trough 1 (also T-Z, 3, ..., 112) T:l Trench station 1 (also T:2, 3, ..., 11) Va Apparent crater volume Vc Continuous ejecta volume Vd Discontinuous ejecta volume Ve Total ejecta volume Vf Fallback volume Vk Cloud volume V1 Apparent lip volume V, Missing crater volume Vp Compressional wave velocity Vt True crater volume Vu Upthrust volume V-l Valley 1 (also V-2, 3, ..., 11) w Yield of explosive ZP Zero Point - effective center of explosive energy u Shear modulus pc Continuous ejecta density pd Discontinuous ejects density of Fallback density .- ‘3 633098335; True crater dc: Epthmst densi- Average met'ac KEY TO SYMBOLS AND ABBREVIATIONS (cont'd) pt True crater density pu Upthrust density 3' Average overburden density xxi LY” ‘ L Sutmt 0f "7" h 2 51351311 beneath t" lies: mum ens-‘8‘: ‘ 1:33 the mud ‘35 W s 1;: E‘ "‘ produced by {5‘ unending 83°“! “1: rating uteorite or a 1 23:11; craters and 9: 13:35:11 and etmc tun} SE at Berbeck, 1971) . 7i ximipel ob‘ ,ect Igh: . e of the geolo: J l' . . Ni Enlosive evq titte fields are t 4:5: . ‘1”- Plinetary u the“ 43' Hematite h "it: an t' “e 500:; (Evil: CHAPTERI INTRODUCTION A. Statement of the Problem An explosion beneath the ground surface of sufficient magnitude and shallow enough depth of burst results in a crater produced by the upward and outward ejection of material and an ejecta field produced by the subsequent deposition of that material on the surrounding ground surface. Whether an explosion is due to an impacting’meteorite or a buried chemical or nuclear detonation, the resulting craters and ejecta fields exhibit a number of Iorphological and structural similarities (Shoemaker, 1963; Roddy, 1968; and Oberbeck, 1971). The principal objective of this investigation is to determine the influence of the geologic setting on the crater and ej ecta field from a buried explosive event. 3.1 ecta fields are important to at least three geotechnical d13‘311311nes: planetary exploration, weapons effects, and excavation ansinceritng. Meteorite impact structures are important P18081181? features on the Moon (Baldwin, 1963), Mars (Mutch and Head, 1975). ”‘1 Mercury (Danielson, 1975). Several impact structures on the Earth are also known. The ejecta fields of these structures consist of miter-1&1 which has been excavated from the crater, thus providing a unique Opportunity to sample depths otherwise inaccessible. mu, eject! distribut‘._ a: magic settings. {tudisttibutim er wéitts for lilitary main. Additional. rm: serve an effective 52:. 2m, for a panic: mama ejecta thi mm. of ejecta 1r, Tmm‘ ninth fro. em 33: 180nm in clean a}! :3 Construct Nrbo' $511,“, “C- (Vorr t he“ ‘ifitl prgdj 3:21:15: the swlogic “‘4'! 4 u.‘ .04 ‘m rkk 1 “a. .‘o: z“file, {ht P! Furthermore, ejecta distributions provide a means of examining sub- surface geologic settings. Rjecta distributions are also important in the assessment of weapons effects for military targets vulnerable to impact and/or burial by ejecta. Additionally, critically placed accumulations of ejecta can serve as effective barriers to troop and vehicular movuent. Thus, for a particular geologic setting relationships are needed to estimate ejecta thickness, ejecta mass per unit area, and number and size of ejecta impacts per unit area as a function of distance and azimuth from the crater. Ejecta distributions are likewise important in excavation engineering where buried explosives are used to construct harbors, canals, railroad or highways cuts, earthvfill dams, etc. (Vortman, 1970). Current ejecta prediction techniques do not take into consideration the geologic setting, except to differentiate between wet or dry soil and rock, thus leading to large prediction uncertainr ties. For example, the prediction of ejecta thickness at a given distance from an explosive detonation incorporates a 2 to 3 order of ‘magnitude azimuthal variation.while the azimuthal variation for a single event is more typically an order of magnitude. By relating saying, sounding, and other distributional features to the geologic setting, reduction of these uncertainties should be possible. B. Previous Research While research has been prolific in the general field of cratering, relatively little attention has been given to ej ecta in? IL ‘ .‘ v. .4-. e V um r...» 0‘1 ”5t 1' £23 Mum hero 1. taresttm mart Earl! no “possible" '- y§g§cg {1?66) of which 5’ 't: 355 based on their a: 311'. gnphysicel, end are ‘me been etudied. 215.51: been and in ‘ :szaft‘m crate Ind cf Nurture of the cr :1!!th blanket. Rodd} :53! mutation of thi: {the the nature and ! 1:5 5‘! Hound surface inflamed fin: to to “we: run. 53!! (1975) Wblis‘e ‘JJ.’ “r. lissi 1° 11:34:: etn 5 ‘45. ”v we" ”381a; fr . C distributions and most is unrelated to the stated problem. Applicable research is reviewed here. 1. Terrestrial Impact Structures Nearly 100 "possible" terrestrial impact structures were listed by Freebarg (1966) of which 52 were considered "probable" by Short and Bunch (1968) based on their analysis of relevant morphological, structural, geophysical, and petrological data. While many of these structures have been studied, only the ej ecta field of Meteor Crater, Arizona, has been mapped in any detail. Shoemaker (1963) mapped the geology of this crater and ejecta field demonstrating the overturned Inclinal structure of the crater lip and the inverted stratigraphy of the ejecta blanket. Roddy, et al. (1975) recently concluded an extensive examination of this ejecta blanket, drilling some 160 holes to determine the nature and thickness of its stratigraphy and related uI’M-ft of the ground surface. They found the inverted stratigraphy °f the overturned flap to consist of continuous layered units out to “at 3 crater radii. Moore (1976) published an analysis of over 50 high to hyper- "10city missile impact structures at White Sands Missile Range, New “Rico. Craters ranging from 2 to 10 m in diameter and their ejecta fl-elds were mapped with inverted stratigraphy observed . The 1“Nuance of material properties of the ground surface on the dilensions and characteristics of the craters and ejecta fields was dhonstrated . r-I I'I 2. Laboratory Cratering Experiments Laboratory impact and explosive cratering experiments are useful in studying source parameters (charge size and position, projectile impact mass, angle, and velocity, etc.) and site parameters (material properties, layering, terrain, etc.) since these can be varied in a controlled manner and the resulting crater and ej ecta fields are readily measured. The primary limitation of these experiments is in scaling up the results to "real world" structures. Nevertheless, a significant amount of experimentation has been performed, but unfortunately with little emphasis on ejecta. Johnson, et al. (1971) using gram-size charges in a homogeneous, 4!? send d-onstrated that ejection processes were orderly. Bj ecta exit angles increased and velocities decreased regularly as depth of burst increased while at the same scaled depth of burst exit angles We nearly identical. Vesic, et al. (1967, 1972) detonated gram-size charges in a ”finally designed test bed with a vertical window to obtain high- 'Ned cinema records of the events. They determined that material ”Warties, layering, and terrain have important effects on the f"'liation of craters and presumably ejecta fields, although the latter "ts not measured. Piekutowski (1974) and Andrews (1975), using ulilar techniques, studied the formation of craters and ej ecta fields in dry and wet sand. They identified zones of ejecta origin and mMerved ejection processes to be orderly. Beyond the crater lip individual sand grains, traveling ballistic trajectories, were ferment-.13 Outfit. :ch :i the 111: was 3‘. mimru‘ty to tan-size unexcused (Post, 1‘ 1": Salt, et el. (19. 175$? ejection and awg E3313 Butt-send terg Le rallels with liver“. "1 but end bum 3' m-k?1031\'g 3.. LL.» . ensue and nuclear m; , k“ '3‘“ Positions . 1’: a5 burst (Vane. 19 't‘L' .« km N hires. it 3&2 "R’s. .- i * a) m: it: n 3‘ (303 73113 ' J '4 at . ‘1 a “.2 {L3 Tm deposited in a steadily outward progressing pattern. Inverted stratigraphy of the lip was observed and ejecta distributions compared favorably to ton-size field events when appropriate scaling techniques were used (Post, 1974). Both Gault, et al. (1968) and Stoffler, et a1. (1975) observed the orderly ejection and deposition of ejecta from hypervelocity impacts into quartz-sand targets. Many of the resulting moropholog- ical and structural features of their craters and ejecta fields have close parallels with laboratory explosive events, as well as larger terrestrial impact and buried explosive events. 3. High-Explosive and Nuclear Field Tests During the past 30 years there have been a large number of highrexplosive and nuclear field tests ranging from 1/4 kg to 15 MT and with charge positions varying over a wide range of heights and depths of burst (Vaile, 1961; Vortman, 1969; and Circeo, 1969). Carlson and Jones (1965) analyzed ejecta distributions from several nuclear and high-explosive events in desert alluvium. They found mass distributions of ejecta similar at the same scaled distance (R/Ra)* and nearly identical for events at the same scaled depth of burst (DOB/W1/3). In addition, a number of investigators including Sakharov, at al. (1959), Chabai (1962), Ahlers (1962), Diehl and Jones (1964), and Carlson and Rewell (1970) have studied ejecta mechanisms (origins) using tracers preplaced in the region to be cratered. In nearly all *See Key to Symbols and Abbreviations for definitions of terms. ”truer! are distribute-i 1::th dispersion. e pared to benctnark t" @1351), Cherry (136‘) IE2“. especially for 1 3' asunined the effec‘ rind their size and ye List-def ta distributic tamed ejecta distrib' "healer (1963) van Infe'nried nuclear 1 333133? Ind structural "2‘ 3133! then crater “Rn- r. :Seéan (R cases tracers were distributed radially outward from SGZ with only limited azimuthal dispersion even for sand-size tracers. These data have been used to benchmark theoretical calculations by Hess and Nordyke (1961), Cherry (1967), and Terhune and Stubbs (1970) with some success, especially for relatively homogeneous media. Sherwood (1967) has examined the effect of drag on ejecta fragments as a function of their size and velocity and applied corrections to calculated ejecta distributions bringing them closer to agreement 'with measured ejecta distributions. Shoemaker (1963) was first to map the structure and strati- graphy of a buried nuclear event and favorably compared the inverted stratigraphy and structural deformation of the crater lip to Mbteor Crater. Since then crater lips of several other buried nuclear events have been mapped; Sedan (Richards, 1964), Danny Boy (Short, 1964), Sulky (Lutton and Girucky, 1966), and Cabriolet (Fransden, 1970). Each exhibited an overturned flap with inverted stratigraphy and structural deformations differing only in detail, presumably due to differences in the geologic setting. During the past 10 years Roddy (1970 and 1973) has mapped a number of high-explosive surface events (20 to 500 tons) favorably comparing their deformational, morphological, and stratigraphic characteristics to terrestrial and extraterrestrial impact structures. Johnson (1962) studied 12 buried high-explosive events in basalt. He observed that as crater size decreased crater shape became increasingly influenced by joint spacing. On several events one new rays were aligrze r2112? of the jointing p: 'z'r 255‘ correlated eje sat-had: with ujor :- i. The Schooner Event he Schooner event, a :‘eiih'. on 8 December 19*. :Ils' Energy Research hrehmn for the den :5" m 5cm” d, mm“! designed r ‘ ev or two ejecta rays were aligned with joint trends; but local variability of the jointing produced conflicting results. Kenny and Carlson (1968) correlated ejecta rays from surface high-explosive events in basalt with major joint trends. C. The Schooner Event The Schooner event, a buried nuclear experiment, was detonated at 0800 PST on 8 December 1968 at Nevada Test Site. Schooner was executed by the University of California Lawrence Livermore Laboratory for the U.S. Energy Research and Development Agency as part of the Plowshare Program for the development of nuclear excavation techniques. The Schooner device was a thermonuclear (fission-fusion) source, specially designed for Plowshare excavation, with a measured yield of 31 i I: If. The device canister was implaced in an encased hole such that the zero point (2P) or depth of burst (DOB) was at 108.2 m. The device was ate-ed with a grout-gravel mix several weeks prior to detonation to ensure compatability with the surrounding media. The primary objectives of the Schooner experiment were to acquire crater growth and dimensional data to benchmark theoretical calculations and to determine the fractional release and transport of radionuclides. Site geology, consisting of a partially saturated, layered sequence of welded and nonwelded tuffs, was specially selected to res-ble the Transistt-ian Canal Region more closely than sites of previous buried nuclear events. Lessler (1968) has described individual experiments and a su-ary of results has been 115379-15 (1973). 5 1: a efecta field. 3. Watch to the Pt tile research to 13:. mix maxed efetta ' masses: that: is l t’.‘.. “’44“: and structure of 'seo 1’ attired data rcla: in; :1! :2: .13! 13 ulativf reported by Tewes (1970). Benny (1970) presented general data on the crater and ej ecta field. D. Approach to the Problem While research to date indicates that to a first degree explosively produced ejecta fields are the result of an ordered set of processes; there is little specific information available on the morphology and structure of any large crater and ej ecta field and only scattered data relating the geologic setting to their formation. The Schooner event is uniquely qualified to address this problem. The geologic setting has been well documented (Chapter II) and the surface is relatively level and free of vegetation. Using Schooner results, the stated problem is addressed in three consecutive steps. First, the crater and ejecta field are 8yatematically mapped and analyzed; dimensionally (Chapter IV), morphologically (Chapter V), and stratigraphically and structurally (Chapters VI and VIII). Second, major features of the crater and ejecta field are compared to key parameters of the geologic setting to establish cause and effect relationships (Chapter VIII). Third, these features and relationships are assessed against available transient data (Chapter III) to construct a time history of, and to infer Processes responsible for, the formation of the Schooner crater and ejecta field (Chapter IX)- r- ~.' vim-0 L rzysiagrap'ar 12 timer site is l. zzfsmia Test Site at" e htaiig. 1). 55710- 29.: Level and modem c ;..':. cm ‘1 ...,...J , is approxia ...izzssmed plateau t1 The plateau has a G... k. I" ..t :0 fully contain 1 \ . I ~ >11: " “ Btends b27035 “”436 (Fig. 3). is, ~°?°§fi?':ic and: {; 5:33 ‘ ‘Ms 0 .0 5 l3) Vith a: 5‘». ‘43! L” 4’55 the crater : N “ ‘ EL’, Strea Vi“ ‘54:: u I ' . 3&3. 433“ m‘ -' CHAPTER II GEOLOGIC SETTING A. Physiography The Schooner site is located on Pahute Mesa in the northwest corner of Nevada Test Site approximately 200 km northwest of Las vegas, Nevada (Fig. l). Schooner SGZ, with elevation 1695.4 m above mean sea level and geodetic coordinates of N 37°20'36.3l87" and W 1160 33'57.1419", is approximately centered on a gently undulating, slightly dissected plateau along the northwestern edge of Pahute Mesa (Fig. 2). The plateau has a minimum radius of 800 m about SGZ, sufficient to fully contain the continuous ejecta blanket while to the south it extends beyond 2.4 km, sufficient to contain maximum ejecta ranges (Pig. 3). The topographic gradient is constant across SGZ curving from azimuth 295° to 135° with an average 1 l/2° slope. Maximum elevation decrease across the crater and continuous ejecta blanket is 7 and 25 m, respectively. Stream valleys approximately 450 m,to the east and southeast produce local elevation changes up to 18 m. The ground surface is covered by soil ranging from 2 m.in thickness on the south and east to less than 1/3 m on the west and north where bedrock is exposed locally. The soil unit supports some grasses and small bushes not exceeding 1 m in height. 10 scnoouea SITE 116:30’ “6°15“ 116 00' N ' I roe-eo-.._.,-..-l ’/ \. I i = . 4 my}, I . .E'ko! / \~---‘ 056 : I l -l i / . \n ‘5 I I PReno : / \. J ‘9... .I L-—-_.____. L 37°15. .\ NEVADA V \ .3 Rain“, i s\ / g ' I . °° l \ I \ ' ' ‘ s . I ‘ °'\ Nevada «00‘ ~ \ | .' T.“ S“. J‘.‘ K. Backboard | ' \o. g r", ngmbet :3- Meso , l \5“ “9" i M;- a I N d ’0. 2: 100 0 too zoo Inn \ "a a “0"”; g S 37000. “LL—l \ Test Site Boundary —-)l £5 § 8 .. I d 3 . \ I ~' : 5 2" F , , . I \ . 3? ‘\ ," '5 E Lincoln \ l ”t ,' a' l County . I ' ,’ Frenchmen I-"-"°_ I ‘0‘, O. ‘..‘.o' Lak. ('7 C'C'k ' ' new” ' . \. ‘ County Ina-«7, £35k..." m. l' . o ' 0' . o 36 45' . ' .'99J l I . f .s ‘.-.”—o—o—--.-.‘ ' ' ' H") 93 ‘ Lump wan. L Mum, . . ' I 0 25 km 1 L l L a I Mature 1. Index Map - Nevada Test Site, Pahute Mesa, and Schooner Site . .(nouh.-fldu ..n‘ 11¢“. £4 4-‘ f“ u 11 SCHOONER SGZ u—n— _ ._,- _.-” V From Five Kilometers Southeast V "A , ‘ ‘ vamp ; “at. k ‘9” From Four Hundred Meters Northeast “3"“ 2' Two Views of Schooner SGZ Area (Lawrence Livermore Laboratory Photos) 12 \ Q/F‘.V\L I “v\%>%%\\( \ t . I‘L \ , s°°° §§§3 /‘\—\ (Elevations In he. MSL) Figur. 3. Topography of Schooner Plateau with Average Crater and Continuous Ejecta Boundary Indicated !. Intimphr Trimmer lite is . zeta: boundary of the 1 atheist of the sort? in the entire Scheme 2min tuffe (Treil emf the Thirsty cum 3'“ 3mm Haber of n 13:1 underlies the ‘~-‘- its table I. g. 3! write: Seclogy I}: I , '1' ‘ 11‘3” “Win: Q .-_ o ”‘5‘ “We the bots} Dr‘r‘l‘t; N" M ”“1011 is I h. «.2: if t. a hln lie-2‘ 4e. 1mm“ the 8 II . )amv€ m M1023 13 B. Stratigraphy The Schooner site is located approximately 6 km northwest of the western boundary of the Silent Canyon Caldera and less than 5 km north-northeast of the northeastern boundary of the Black Mountain Caldera. The entire Schooner plateau is underlain by nearly flat- lying ash-flow tuffs (Trail Ridge, Spearhead, and Rocket Wash Members of the Thirsty Canyon Tuff) from the Black Mountain Caldera. The Grouse Canyon Member of the Belted Range Tuff from the Silent Canyon Caldera underlies the Thirsty Canyon Tuff to an average depth of 170 m. Water table is 260 m below the surface. The surface geology was mapped by the U. S. Geological Survey as part of a larger mapping program covering most of Pahute Mesa. while few exposures are present on the plateau surface, good exposures are present along the bordering cliffs and a particularly good stratigraphic section is present 1 km southwest of Schooner SGZ. A portion of the Trail Ridge Quandrangle Map (Christiansen and Noble, 1968) that includes the Schooner site is reproduced in Figure 4. Subsurface geology was obtained primarily from eight drill holes within 350 m of SGZ (see Figure 5 for locations and Table l for drill hole data). The deepest hole, PM #2, penetrated over 1260 m of tuff and bottomed at 2677 m in granodiorite porphyry (Hasler and Byers, 1965). Two other holes, UeZOu-l and 3, examined the subsurface geology and physical properties of the media over predicted depths of disturbance from the Schooner event (Sargent and Jenkins, 1968). Four additional holes (UZOu-l, 2, 3, and II) were drilled for the \ 14 CUE ‘LLUV'UM ND COLLUVIUM SPEARHEAD MEMBER LAVAS OF mason CLIFF GROUSE CANYON MEMBER or BELTED RANGETUFF TRML RIDGE MEMBER ROCKET WASH MEMBER TIMBER MOUNTAIN TUFF TUFFACEOUS SANDSTONE AND BEDDED TUFF Figure lo. Geologic -Map of the~Schooner Plateau (After Christiansen and Noble, 1968) "“16! AWARE-IT; 15 ‘2 ‘e u.2o..-3 100 In J Figure 5. mum: of Exploratory Drill Boles Near Schooner Site SCHOOhfl as 3.1 31318! bl Ll. h- an .n S knee. in r. I- $11 II '4 Ni 2'15 2‘} I! t: 31:: Q . I “5' “A I u 1i; “P ”W 112 I 3 I :II,‘ '4). ‘if L“! , ..} :I . 4A; ‘ I . K "I . " 3““: :13‘.‘ ‘3 . 3 1-: ‘fl‘} “Cl .. “ I j “ | p ”1“ “J . fl 9. ML“; 101 16 TABLE 1 SCHOONER DRILL HOLE DATA location Collar Distance (1) 51' (Invade new. From Role Total Date Drill Sample 0009M" Reference Ms- sutt Int. stunt-or nu. Depth um Method Method tit-1 ' mtiom Cased .) (a) 562 (m) (in . ) (I) Lost HI '2 l9“,562 1703.5 263 26 to 2677 5]“ Rotary air, Cuttings C,E.D,V, Healer 6 1526.655 6 1/8 soap 6 water 5 inter- 3D,P,Y Dyers (1965) led below mittant 1961 m coring (38 runs, total 66 m) 010a ammo“ 1695.6 0 52 137 8/68 on .1: Cuttings c.o.e.r Ramspott l529,300.0 w/vacuum at 3 a (1968) intervals UsZOa-l I965,00S.7 1697.6 322 3 5/8 229 6/66 Mud Continuous C,D,3D* Sargent 6 2529,645.9 core to TD SU,II,T.! Jenkins (1968) “0203-3 l963,962.8 1695.1 21 9 7/6 152 7/68 Dry Air Cuttings plus C,D,Dl., " 1529,2664 w/vacuI- 13 core runs SU,SD, nominally 1.5 Ll to 3 m in length, 17 m recovered ”IO-‘1 ”66.066J 1695.3 21 6 3/6 126 10/68 Rotary with Cuttings at C,D,Y Putty-In, 1529.3“.0 Davis Mix intervals 3 m Darrill. 6 Rush (1969) "2°“! Nazis 1695.2 63 6 3/4 112 10/68 Rotary with Continuous c.n.r, " 3319.3”.4 Davis Nix ton to 11) 3D+,V+,N DIN-3 MIIOIJ 1695.3 66 6 3/6 79 1.0/68 Rotary with none C,D.T " I529.‘20.6 capressed air to 30 m Davis Mix below "2"“ mama 1695.6 as 6 all. 4.6 10/68 " not. (2.0.! " 529,566.; ”a” (1) ”fish used for geophysical legs 9 3 Caliper I : G_e neutron P : Fluid density Y = Directional DL: Interval density so: Sei-ic uphole D 2 Density P : Dore hole SD: Seismic downhole photon-oh! 3D: an "19;“, t : Partial logs obtained 1' : Neutron-neutron V 2 Continuous velocity + ° Suitable logs not obtained 3 : Electric an (a 1" ' "11W! a"; uni! to ermine de: 23:: region (Purtym. 22'}; as also emit; It" haiditiou 5 other :ere' were drilled f3? 22:55:: correlations .T-I islet, 1965; tel”): 5136?; and Cello-2 1e geology at Sc‘aoo' 32157835 of units {T 1332:: with the areal muting of the cr 4"" “ailing their #:2335155”, and 2‘. e \I .-. 4‘3: r - , “5‘8: “1°“ are I 27334 . _«C “its EQQQ 17 present study to examine detailed‘variations in stratigraphy across the crater region (Purtymn, et al., 1969). The Schooner emplacement hole (UZOu) was also sampled and geologically studied (Ramspott, 1968). In addition 5 other deep holes within 6 km east and southeast of Schooner were drilled for other projects; but provide areal stratigraphic correlations (020m to 1264 m, Orkild, 1969; UeZOj to 1734 m, Hasler, 1965; Ue20p to 1524 m, Jenkins, 1969; U20p to 998 m, Jenkins, 1969; and Ue20u-2 to 381 m, Ramspott, 1968). The geology at Schooner site is subdivided into four over- lapping systaas of units (Fig. 6): stratigraphic units for correlation with the areal geology, mapping units for detailed geologic mapping of the crater and ej ecta field, physical property units for examining their effect on cratering, ejection, and deposi- tional processes, and ejecta units for describing the surface morphology of the ej ecta field. Listed below are brief descriptions of the five major stratigraphic units encountered at Schooner from Christiansen and Noble (1968) and Orkild, et a1. (1969). Trail Ridge Member (0 - 43.3 m): Multiple-flow simple cooling unit of metaluminous to peraluminous silicic ash-flow tuff underlain by pumice-rich air-fall tuff at base. Ash-flow tuff densely to moderately welded, mainly devitrified, but with glassy base. Spearhead Member (43.3 - 60.7 m): Simple cooling unit of comenditic to trachytic soda rhyolitic ash-flow tuff underlain by pmnice-rich air-fall tuff. Ash-flow tuff ranges from nonwelded to _ . .- -<_e \[ I ...'.‘. L s -' v.- d“ ' . ...‘ ~ ..— —’ l . . ' _:I I53“ I" I ~—-— _ a 'e—_ e we we .r 1‘. IF isUE I] “—u 33‘: h.. 1:3: 392-“ K \ file-m \ R \ a: ‘ \ \ ’32! 57 If” \ ‘l 1: \ ”4.53 I} :‘I I} I"! "JV-A» “M .‘I; . a. ' 18 Pigu11II6. STRATIGRAPHIC MAPPING UNITS UNITS PHYSICAL EJECTA _ PROPERTY UNITS roauanos senses UNIT iffif'f" UNITS L8 0 as as —l 3 oensva L mam o TRAIL L wstoso c Iuoot K cmvou TU“ s 219 332 P . B {0 TUFF . 35.7 3&7 39 3 Y .1 Y 38.7 ' T 4L1 ‘13 WEAKLY 9 49J wsLoto 7 SPEARHEAD 53” TUFF V 576 C eo7 i 6L9 F ROCKET I W N vasn 712 E p sou- 771 s 7&6 Li 2 watoso 818 3 TUFF unnaueo 905 4 933 5 957 a s Iooo 7 :’ 1021 setrso ‘013 s onouse o DENSELY L RANGE o CANYON WELDED C TU'F TUFF K s Correlation between Stratigraphic, Mapping, Physical Property, and Ejecta Units at Schooner Site geld, devitrified a at zero It to? W5 5355 It! iris: lash Haber W :rxsada rhyolitic to 27.3. air-fall ruff. use zones, vitric. 1:127: and base. heed Faber 5‘95 Sediaents with ti ~3_":I. in“ 5&an Faber \\ :Tltritit 1513.51“ tuff 55": Eu mine. m inflation of Itrat ‘- - “qu scz in an item.” Ptofilee s. u...- x-Jtlt P! #2, the ‘8 3:43: . 19 weakly welded, devitrified and in part vapor-phase altered, thin glassy zones at top and base. Rocket Wash Member (60.7 - 77.1 m): Compound cooling unit of trachytic soda rhyolitic to comenditic ash-flow tuff underlain by pumice-rich, air-fall tuff. Ash-flow tuff primarily nonwelded, some weakly welded zones, vitric, in part vapor-phase altered, thin glassy zones at top and base. Unnamed Member (77.1 - 100.0 m): Reworked bedded tuff and tuffaceous sediments with minor nonwelded ash-flow (and air-fall?) tuff layers. Grouse Canyon Member (100.0 - 148.1 In): Compound cooling unit of comenditic ash-flow tuff, moderately to densely welded, devitri- fied with glassy base. Prominent compaction and flow foliation; lenticular gas cavities containing vapor-phase crystals. Correlation of stratigraphic units between drill holes within 350 m of Schooner SGZ is presented in Figure 7 with average apparent and true crater profiles superimposed for reference. With the exception at PM #2, the major units are continuous and uniformly distributed. Variations in thickness across the cratered region range from :62 for the Trail Ridge to 1162 for the Spearhead, with the majority of the variation contained within the weathered and reworked tuff horizons. Sargent and Jenkins (1968) maintain that differences between PM #2 and the remaining sections are real and probably the result of pre-Thirsty Canyon topography. The original interpretation for the v-o- . 'TP"'--’--- oe“. b h I vAv. °(Ioe.‘I-mfl .aau‘ Jo‘.h ..h ‘..V h!l.(‘t( l I. C. n no.1 . . m. .. mt . see I I I s‘» .a.~‘ 1 IL. 1. I.. s .w. I!» | L m .‘ -0--. . ~ . IIII .\ .3 Noun \ ouum nogosum neon—ad news: owneouwuueuum mo souunnouuou .5 9.53m :5 m .Cuh QC zoabmm ho MZEA Zn 25$: SHZOOEOm 20mm HOZ4 . to dbl [H ee . IL 80— — I‘IIIII IIIIIIIII :0:0.I .0 .30 .50 00—0; :t‘ VO£I°° A: see- ENH— - «I "352 .. . J, . . u 0. “nu-“NF - i s j _ . zo>z15) ‘0‘! u. b h ‘a. m.2m-mvx ‘ III! III-ll \ I s \ . \ e \ l . ll... ll All! / ..r-\ I . . ‘ \ .‘l. . \ ‘ lxlul\i \ ..lll‘ . ll \ ll” lIV- \ l \ I \ \ Q I I 31 sauaqu ooonmnnwum osocuooc scum oonuoeoc as neuumoouon noume monsoon n.~ ou m.o scum enoouusm wauuso> one useseoaw>wn vase: Eoc— 1J 4 . A on c l/ \. ./ \l . {\irL / J \ \ \ \ x / \l . m s a \ /\ I 4 .s ’\ l/ v ' \ s I \ \l \s use Q; / l \ (t I . .\ use . lII \ . .1s a. \ ~ \I . \I\I\ usnno Ill / / I l m2¢mhh l// «.2355. ozaox I ... 1‘ .NH enough (I d r (\u \l’ l _ . x \ \ \r..\ 8.2 s I I i . k n 930.— .x 00.0.— N9». :. Ejection Tenthg began at 1'- Elre‘tiil.’ above SC: 5 maize and still risi: 3.3150" SGZ followe tinted along an I? '13... The four cente tee-tire lawn! area ‘ Miriam ejecta ”3&5! Rohrer (1972) 11“-‘§213t-sorrthwest to l! 3.1 sec a broad Eim’ ° 4.3m centered we; t-"=.>trsisted until 5. «‘3in 't ‘PPIOI 5;: . ‘45 to 600 ' fr“ Sr: b}. r «worsened; but nc *- m ' "V . We vertical \ Eu. Rafi at 1.9 sec p! til “94 14.1%, C). 1". re . ' . H 3' {than d Visible 1 32 2. Ejection Venting began at 1.75 sec (Fig. 10b) with the mound surface 88 m vertically above SGZ and approximately 9 m high at the final crater edge and still rising at 2 m/sec. First venting occurred directly above SGZ followed at 1.88 sec by three new centers equally spaced along an are approximately 60 m southwest of SGZ (Fig. 12). The four centers had coalesced by 1.96 sec and by 2.10 see the entire mound area was engulfed in a plasma of incandescent gases and luminous ejecta fragments with highest temperature recorded by Rohrer (1972) of 2590°C. Early vent patterns paralled the northeast-southwest mound elongation. By 2.1 sec a broad three-lobed triangular blanket of plasma had developed centered approximately 60 m southwest of SGZ. This pattern persisted until 5.4 sec with the southwest lobe developing into a luminous jet approximately 60 m above the ground surface and extending to 600 m from SGZ by 7.9 sec (Fig. 10c). A few other jets were also observed; but none extended out as far nor persisted as long. Only one vertical vent not obscured by the mound disassembly was observed at 1.9 sec propagating downward towards the ground surface (Fig. 10b, c). This vent between 115° and 125° was closely aligned with the southeast plasma lobe of Figure 12. The plasma blanket remained visible until 8.5 sec at which time the partially disassembled mound was over 500 m high. Between 3 and 5 see several thousand luminous masses of ej ecta up to 3 m across exited in ballistic trajectories from the upper 4am $2-! l I: .-. ‘ e E . e mfi the sound thro: 5317, nit angles we: 25'??? to £00 Ir’sec. meta near 55° wail] refine“ ejecta nsse. rflig'zt and ease ixpa 5135‘. the last 13111101: “51:! Presented :5“ “5m mares: Emma glass (1 “In. it later times, RTE! probably f' .3! :1 the P133“; 1 trial 51mm or its Araf- “’ the of .5 33 portion of the mound through the plasma blanket (Fig. 10d, e). Initially, exit angles were near vertical with velocities on the order of 300 to 400 m/sec. With time, exit angles gradually decreased to near 65° while velocities quickly decreased to 100 m/sec. Many of these ej ecta masses remained luminous for up to one-half of their flight and some impacted in this condition. Viewed from the southeast the last luminous impact was recorded at 22 sec. Evidence presented in Chapter VII indicates that most impact- ing ej ecta masses apparently were nonluminous; i.e. they were not coated with fused glass (solidified plasma). Either they exited from the mound at later times, presumably when plasma temperatures were lower, or more probably from portions of the mound which were not affected by the plasma; i.e. from the outer mound surface beneath the plasma blanket or from fringes of the flap segments. Another type of ej ecta mass, termed streamers, were observed to exit the partially disassembled mound in ballistic trajectories beginning at 4 sec. These masses, several hundred to perhaps a thousand in number and ranging up to 3 or across, differed from other ej ecta masses in that they formed thick contrails of dust (ej ecta fines), some up to 50 m in diameter (Fig. lOe, f, and 11a). Some streamers were luminous. Exit angles and velocities averaged between 60° to 70° and 60 to 90 m/sec, respectively. Streamers impacted consistently behind the previously discussed welded blocks with maximum observed impact at 700 m and 19 sec. thin resolution : :szejecta, belie Eritrean steppe. m: to having co: “753% nit "c". 5« loosition 3m titer initial ‘ insured first by t litated during the 1:35 the base Surge :; Sam ““388 aft h N teased. Data b "-0 m f“ of 34 On high resolution photography streamers are seen to consist of a core of ejecta, believed to be compressed, nonwelded tuff. A number of streamers stopped forming contrails prior to impact, possibly due to having cores of a more denser, weakly welded tuff; i.e. mapping unit "c". 3. Deposition Soon after initial venting, details of the mound disassembly became obscured first by the plasma, second by the large quantity of dust generated during the mound breakup, and third (and later) by the buildup of the base surge and cloud. As a result, neither the Schooner crater nor the majority of the ej ecta field were observable until several minutes after detonation by which time all movement of ejecta had ceased. Data presented in Chapters IV-VII will show that over 902 of the ejecta was deposited in a series of overturned mound flaps arranged radially outward like spokes about a hub (the crater). These flaps were probably emplaced by 15 see as inferred from observations of the base surge. Individual ej ecta masses were observed impacting the ground surface in front of the base surge from 11 to 71 sec over ranges from 380 to 2150 m (Fig. 11). Upon impact large secondary ejecta sprays resulted with cloud heights and diameters growing as large as 100 m. These ejectamasses are typically associated with the secondary craters and secondary ej ecta fields which they produced. £513; Formation has: surge, a do; r357 the flap segue: reared breaking 'nr: The leading er." :reerelxity of 12 t. its 71v. 13). Initi- team‘s-er of lobes 71‘; .3 :4 - .....e..:1g edge. Arte: “‘35-'31 Cauliflower-1 5, “he a? With flat aw “mtg-118d to lir . ...,. h. .1111 * Stabilizar 3’s I '- “’~ M and 4229 2 \ c 7:. ‘5' l3), Photoz: .W ‘ “‘4 int aher «a 9 ‘ scan} .{ ‘ a “ Va ‘A "M _ -;‘ ‘Na 3% ‘n: : N‘ O ‘. ‘6‘ a Q 35 4. Base Surge Formation The base surge, a doughnut-shaped cloud of fines formed primarily by the flap segments impacting the ground surface, was first observed breaking through the disassembled mound area at 13 sec (Fig. 10f). The leading edge of the base surge traveled forward at an average velocity of 12 to 18 m/sec, with forward progress ceasing by 71 sec (Fig. 13). Initially the leading edge of the base surge exhibited a number of lobes extending 150 to 200 m in front of the average leading edge. After 21 sec these protrusions became muted and a general cauliflower-like pattern developed. Early lobes tended to line up with flap segments, while the latter-time and broader lobes tended to line up between flap segments. Vertical stabilization occurred by 4 min at a mean height and diameter of 670 and 4220 m (Gudiksen, 1970). The final base surge pattern (Fig. 13), photographed several days after the event, indicates that after stabilization southerly surface winds inhibited further spreading along the south. To the north and northeast, base surge deposits were pushed downwind and are indistinguishable from cloud deposits. 5. Cloud Formation The cloud began to develop soon after venting and had stabilized by 4 min at a mean height and diameter of 3960 and 2400 m respectively (Gudiksen, 1970). The base of the cloud from ground surface up to 700 m moved generally north at l to 5 m/sec while that portion above moved generally northeast at 7 to 18 m/sec. Surface deposits from the cloud were contained within the base surge pattern 36 FINAL FINAL NOTE: Numbers are seconds after detonation Figure 13. Bass Surge Patterns as a Function of Time as Observed from Overhead Time Sequencing Photography .53 .4 i u' n: F J l 'r u 3'. i: :5: northeast Q'- L Ejecta Impacts 1. being mm“ zieu impacts "’6 2.2-25m free e 125).? “mac to altitude c Free :ntinued until 7 3113:!!! SGZ at 15 sec The photographic s, fa: mere autoaeticel ;"all of. equipped wi! 33:23 a black and w': Maintely 8 x 8 h ”infers, 1. 1 c, . Mt"*1: conditions. zEtta hint to we: .3. fl mating be a; In gen " ) and am ‘ C°ntl "9 053m 1’ .'. . . I Hate a )4!“ ph “.1 *5 .3509 $373533 . 37 except in the northeast quadrant where they extended well beyond to 9000 m. B. Ejecta Impacts 1. Mapping Procedures Ejecta impacts were photographically recorded during the Schooner event from a USAF C-130 aircraft tracking east to west at 76 m/ sec and an altitude of 7620 m above ground surface. Photo coverage continued until 71 sec after detonation with the plane passing over SGZ at 15 sec. The photographic system consisted of a standard KC-1(B) mapping camera automatically sequenced at approximately 4 sec intervals and equipped with a 150.895 mm Planigon lens for recording on 23 x 23 cm black and white film. Area covered by a single photo was approximately 8 x 8 km. Photo scale, determined from a set of ground markers, is 1 cm 'I 386 m with a minimum resolution of 3 m under optimum conditions. 2;] ecta impacts were counted on each photograph by overlaying a polar grid scribed in 10° 3 152.4 m areas and marking all new impacts. Counting began on the first photograph exhibiting a visible impact (11 sec) and continued through successive photos until no new impacts were observed. The scribed grid was accurately repositioned on each photograph using recognized terrain markings. Portions of two such photographs are reproduced in Figure 11. 7 in: * 3 «CM' . l 1. listtlbutiou .55 Maul oi 5333 tr. 312-:er 330 to 213' 23.31, nd £7 sec. D; m‘. hinting was main by 23 sec "~ hmIkmdingly, t”: M articularly to Emma local come 3335-: of these was :3; 1111300.! jet , :1! imsiuml p a1 l‘fiin Nl’tially f T5! shah: 1V3 n 38 2. Distribution of Impacts A total of 4383 impacts were counted from 11 to 71 sec over distances from.380 to 2100 m. Figure 14 presents observed impacts at 15, 31, and 47 sec. During the first 31 sec two basic patterns developed. Dominating was the strong concentration of impacts to the southeast which by 23 sec had broadened to include most of the east side. Correspondingly, there was a noticeable lack of impacts to the west and particularly to the northwest. Superimposed on this pattern were numerous local concentrations which changed with time. The most persistent of these was to the southwest in line with the previously mentioned luminous jet. After 31 sec number of impacts decreased and the depositional pattern become more symmetrical with low density areas being partially filled in. The cumulative number of impacts as a function of time for each 10° sector is presented in Figure 15 with ray and valley axes of the continuous ejecta blanket indicated (see Chapter IV for a discussion of the continuous ejecta blanket). There are 8 major and 2 minor concentrations of impacts with intervening laws which correlate reasonably well with valley and ray axes, respectively. That better correlation is not present is possibly due to the fact that ray and valley axes are typically skewed over their total range (indicated by dashed lines in Figure 15) such that the 10° impact- counting sectors seldom match 1:1 with an entire ray or valley axis. Host of the concentrations (with a notable exception at 315°) are recognized by 15 sec and all are well defined by 27 see, when most 39 2% 47'sec 31 sec ljisec NOTE: Each do! (0) represents one elects Impact. 2km Ejecta Impact Distributional Patterns Observed from Overhead Time Sequencing Photography Figure 14. Ah- I ' D e(-O(‘- be! I... 0 I0. Ivl IOn‘O' m‘.. 40 .3252 no souuussm e as mast—35 vaooomnusom us nausea—H swoon— uo uenasz 0523250 .3 ous»: A: .. | Iv OZHBMMm .mO MOZE 3.53 mmfi CC WHAA<> 92¢ Am: WE «Se .35. E 9 3. o> 2. o> 02¢ a; .E :> E :2. ~> 2. n> «33:. v> 2 95¢ 42 o> 1 c... . .-.... z”- _ .. ...... ..4-.u “I. ..l-.-. 4 m ...... . ..... m.-. ....m -h . . '1. ~ 1... Mn| - . . Annnl cl IIIII III'uun ..- unula null. tall. I on: of o: o: 90— on 00 av on o q [q H , . a 1 a d 1 O O n W m A 3 I 3.2 $417»; w 2.. r m V - ta Sum/L 2;. 5:5 3 ..IILRN l o: - mmozé S m: 1 a... o S. 1 $2 ( 382:. no 8. 8. I 3.23%... ...S 7:--. 4 2a - . 8N , cuts. 53 m. 525: Si: 328% z. 1 gflfi ZO_P(ZOPWO CWPI< mW1_P W¢( WCWQIDZ A OWN no L mine received at 1 new pet 19° sec: 3.1352,! factor of 5 :Ls‘mof impacts to t': :rzothe southeast (1? 3527!: is downhill vi; 3353 large luminous ; Ifitmursiom in the “-335 but: is uphil. mzoth southwest ( if?“ “Pacts are kto distance, 13% 'e. Nita: ‘6 between 700 41 sectors have received at least 502 of their total accumulation. Total impacts per 10° sector range from 45 on the west to 226 on the southeast, a factor of 5 variation. In general, there is a notice— able 1ack of impacts to the west, which is uphill. Most impacts occur to the southeast (135°) and secondly to the southwest (225°). The former is downhill while the latter is aligned with the previously discussed large luminous jet in that direction. Both are aligned with outward excursions in the early venting pattern (Fig. 12). Minimum range of impacts is uphill to the west (295°) and maximum range occurs to the southwest (225°). Ejecta impacts are not evenly distributed (Fig. 16). With respect to distance, impacts are peaked near 1200 m and heavily concentrated between 700 m and 1500 m with the 50th percentile near 1000 m. With respect to time, impacts are concentrated between 15 sec and 35 sec, with 502 of the impacts occurring by 25 sec. The slight decrease in impacts between 15 sec and 27 sec is not understood although most 10° sectors are similar, irrespective to either azimuth or Ray-Valley structure (see Chapter IV). Figure 17 compares cumulative distributions of ejecta impacts as a function of distance and time for four pairs of 10° sectors. Pairs (l) and (2) provide good ray and valley contrasts; i.e. axes match the 10° sectors, while pairs (3) and (4) were selected for reasons stated, but also provide fair ray and valley contrasts- may use consumes mo soauossm e no euosesu ease—H uo nopssz agenda-=5 was ween—:2 .3 sun»: (10931“) SLDVdNI 31“.an [IO 62 12.320.95.098 5...: mac. :5 New 20....— coitus 8 s. 3 z 2 9 S a. a a .2 2 2 : a 8: 8: 82 82 8. 3. as c T G d d 1‘ d d. 1 fl 4 1 4 1 ° d d ‘ d d m — 4 ‘ d W T“ d . , .. 2 I 1 L8— 8 1| 1 3 t n 33» N 8 I 1 :5... 93¢ .72 m .: l 8 v 4 was» 1 m :8... 9.2. I a T l 4 8a m V I L m 8 1 \I 2 II I. is d m a 0 .. m 4 r. 8. I (I t i. 1 1 8. x- l l T 1 c2 ~13 9.13 r panda-(um .- :3 ecu: .8. T l l t 8. r L F b b b b r b b D e b b D P b r l 1 L b h b P b b e e h b m b m b b ( '0" ) SLOVdKI CUMULATIVE IMPACTS (percent) CUMULATIVE IMPACTS (percent) (93 ‘°° r I I I I I I I I I T‘Jrr. /,Vy, I I I I H ,-' , 95/ ':///.'/: (v 10) 225° so - ,- 3 .. (”I ..l ' ’1' I v n 195° 70 I- : I, l/ ( ) ..., . l i. I / O ’ . 5° F I! I '/ v 4 85 " :ufHRAm--——f77 If '/ "’ .‘I" ’/ / I- e I . d so .7 , ,‘ ,0 I: I’."' (v.2) 135 I/ // ”I. ..e 20 *- I. :/.// He/ 0 d .’I /"/ (R- I) 185 I.” 10 I- ‘p/ - ’47 0, .« -"‘ L L 1 L l l L 1 1 1 I 1 1 l o .2 4 6 a 1.0 1.2 1.4 1.6 1.8 2.0 2.2 DISTANCE FROM SGZ (km) 100 I I I I I I 9° " . ’ .° . 4" p cm \W a" I ..O’. no F “5”“) ° ( ’// . . Vac/.... ° (as) 285° J " /0/' '"m,/’ m r O... a“ v’l’ ‘ : _." (R 10) 265° /l .' I 60 *- [21.-:1, " b //:: . : " 5° "' 135°(v-2)———-—/ F——" (v.4)as° ‘ / :llg/I I d 30 r- /(./ I ' .' / 95°(R-4) I" so i- ; ' .- 3 : [/4 . I}'/ 20 °' ,’ (v.11) 195° -‘ / 10 a o l 1 L l L J l L l l l L 7 11 Is 19 23 27 31 35 39 43 47 51 55 59 63 67 71 TIME AFTER DETONATION (see) Figure 17. Cumlative Distributions of £1 ecta Impacts for Selected Azimuths as a Function of Distance and Time T22 iisttibution of 227119! axes 9.3:: ‘c‘ro "2 2.13, maxim: r 12:11 Is aligne. gas: with either. 4:1" 9 - .231. 3?1111. 7»,‘ L 3a? ‘3 “1 fart‘ne 25' 3Q m‘lffl later >18; ‘1“\ ‘5321’ Ira 4 CC 3. ‘2 ‘t 3: Q: Azta is s i: r ,1 a\‘ hgah§s ‘QE 7., “an; 5., r x “'5 ”f a a $ It z?!“§ ~. “:2 21"). 35: i"! s 1‘ 44 (1) 85° V-4* 95° R-4 (2) 195° v-11 185° R-l (3) 135° Downhill (V-Z) 285° Uphill (R—9) (4) 225° Maximum impact range (V-lO) 265° Minimum impact range (NR-10) The distribution of impacts is basically different for those ray and valley axes examined, with valley impacts distributed over a greater range. Maximum range is generally greatest downhill, except for V-lO which is aligned with the previously discussed southwest jet. While overall, impacts as a function of time appear insensitive to alignment with either ray or valley axes, the last 252 of impacts is greatest uphill. Thus, it appears that impacts downhill occurred both earlier and farther out than those uphill. This suggests that ejecta masses on the west did one or more of the following: (1) exited the mound later, (2) exited with lower velocities, or (3) traveled higher trajectory paths. 3. Time Sequence of Impacts There were two characteristically different phases in the impact of ejecta as shown in Figure 18. Plotted are time-distant data for all impacts in terms of the range and the weighted mean distance [£(number x distance) % total number]. The first phase consisted of a steadily outward progressing curtain of impacts moving at an average ground speed of 42 m/sec to 1200 m. The second phase, *V-h and R94 are symbols for Valley 4 and Ray 4 respectively. f‘ I I T I 1 I I I.---/I .— ‘- -g‘ -‘ TIME AFTER DETONATION (sec) 45 t 1 I I r 1 r T y I 1 I U 1 T r_ , 7 7s ? ’I/ , ’ I a 71 4 _ .. _/. .. Zn. \ .— \ ‘9’ \ 67 ‘1. — — — _ A 63 , -— _‘ 59 1.1.1:.- — j .. 55 - -‘3‘11‘.‘3- 51 .- ...-= :‘L". 5 4 ‘3 - fl 3.- 3’ - 35 L- -1.‘ r 27 L _ 23 P A A 75 /IMPACT FREQUENCY z - 19 v I :: WEIG:;E£ i5 4’.’ ‘ A a... o (2&2...‘ v g f , 11 ‘-- EXTENDED RANGE 1 L a J g l e 1 L I 1 l A L L J 0 3” 600 900 1200 1500 1800 2100 2400 DISTANCE FROM SGZ (m) Figure 18. Frequency of 21 ecta Impacts 'as a Function of Distance and Time w: ':-. 2‘. sec, cons trrczress of the c :5 tbstndally char 3:7. bte that the i mg a given ti: curing Eton a tint 11:: 3? sec. Hui: :51; xnxed “ea: t 21'. 13 either side. :3; in an 95113;. ‘. . \. a“ . _ . \n Rt. ‘34:: . “°- of t: 46 beginning by 27 sec, consisted of a series of oscillations in the forward progress of the curtain with neither mean nor maximum range values substantially changing throughout the remaining depositional history. Note that the initiation of the second phase occurs approximately when 502 of all impacts have occurred (Fig. 16). During a given time interval impacts occurred over a distance range varying from a minimum of 600 m at 11 sec to a maximum of 1220 m at 39 sec. Maximum number of impacts during a given time interval occurred near the weighted mean distance and decreased smoothly to either side. Extended ranges on either side of the plotted data are estimates to account for those impacts obscured by the cloud and base surge. Only beyond 50 sec do the number of these impacts reach 202 of the total. 33535.0. CHARACTE‘ L Definition of hidinition, the “3713111 ground our 1'33 W110! above in 13m: crater Ind . “d “511?“! Photogr. ”in n "”‘fied pro 365' ft“ m 15013“ in} gen u; Iod 2“” to 571501: . 1‘ Cute: t! “Karen: Ct; 3:5 Q races,” .0 “a .. Vita» N . “it ., Mlmation CHAPTER IV DIMENSIONAL CHARACTERISTICS OF THE CRATER AND EJECTA FIELD .A. Definition of Major Features By definition, the visible portion of the Schooner crater below original ground surface is termed the apparent crater while the visible portion above is termed the apparent lip. Major features of the Schooner crater and ejecta field can be seen in the aerial over- head snd oblique photographs of Figures 19 through 22. Figure 23 presents an averaged profile of the Schooner crater and ejecta field prepared from the isopach map of Figure 24 with major features defined. Terms are modified from Hansen, et a1. (1964) and listed in the Key to Symbols and Abbreviations. A 1. Crater The apparent crater is the void resulting from the sum of the cratering processes modified to a minor extent by post-event processes such as vater and wind transport of ejecta fines into and within the crater, consolidation of the bulked fallback, mass slumping of ejecta from.the crater rim, and tumbling of individual ejecta blocks down the crater sides. The true crater lies outside and below the apparent crater being the boundary beyond which no significant dislocation of material has occurred. 0n Schooner, the true crater is exposed along the upper sides of the apparent crater. Between the true and apparent crater lies the fallback which is the result of a number of cratering processes including displacement 47 x u ’l J 4‘: ”in BASE SURGE AND CIKNHDIDEPCEHTS DISCONTINUOUS EJECTA FIELD / 0 j (ms P»... 5 sends. Lumen... Albuquemue, NM) ‘0 1000 Figure 19. High Altitude Aerial Photograph of the Schooner Crater and Ejecta Field ( 969 ”Info 5 Amadeus Aeflol Serve a VI. Covlno, Figure 20. Intermediate Altitude Aerial Photograph of the Schooner Crater and Ejecta Field Bah.) n. s . o. i ‘ill‘d ill I . (1973 Photo by Williamson Alrmh, Son's Durban. CA) Figure 21. Low Altitude Aerial Photograph of the Schooner Crater end Ejecta Field Looking North [Cru'u II 32.6!" Rim to Rhl] (1969 Photos by American Aerial Surveys, W. Covino, CA) Figure 22. Aerial Oblique Photographs of the Schooner Crater and Ejecta Field I! O (sundae :I\ 2: II us fa, M "\ 52 Amcouuuffiunfi‘ use nHon—ahm ou hou— oomv 33m uuounm use noumuo nocoozom 0.3 no 3395 3939.4 .2 snow: 35 mugs .HZHOA OMEN ma 20mm HUZLr-p-.......LFLL..+_....’...L_...._... p .— (m) EIOVJHHS CINHOHD 'IVNIDIHO AlO'IEIH/SIAOHV SIDNVLSICI S3 R109. R10C (eleveolom In two) 500 (conroun mrtnvu. as FT 1 m curse. I n our) Figure 24. Modified Isopach Map of Schooner Crater and 2:) acts Blanket with Skewed Ray and Valley Axes Indicated . u‘ A !" and ~11 tr! «e 54 of material within the crater, ballistic return of material originally ejected, collapse of portions of the mound after venting, failure of portions of the overturned flap along the crater rim, and fallout of fines from the base surge and cloud. Outside and below the true crater lie in succession the rupture, plastic, and elastic zones. Each of these zones is the imprint of a continually decreasing stress field; thus, each is imprecise and difficult to delineate even where drilling, excavation, and geophysical techniques are employed. For Schooner, these zones remain undefined. 2. Lip The apparent lip is composed of the true lip, formed by the upthrust and partially relaxed ground surface, overlain by material ejected from the crater. The true lip peaks inside the crater lip crest (at R31 of Figure 23) and drops off rapidly, becoming ‘negligible by 300 m (~2.5 Ra)' Ejecta deposits peak at the crater lip crest and drop off more gradually. They extend continuously out to the continuous ejecta boundary (Rab)! which averages 510 m (NA Ra)’ and discontinuously to the maximum.ejecta range (Rm), which ‘reaches 2150 m (~16.5 Ra) in at least one direction. There are eleven distinct topographic highs (crests) and intervening topographic lows (troughs) spaced unevenly along the crater rim. Each crest and trough gives way outward on a 1:1 basis to radial concentrations of ej ecta (rays) and intervening sectors smith little ejecta (valleys) (Fig. 20). Rays and valleys extend out to the continuous ejecta boundary and, as will be demonstrated in 55 Chapter VII, can be traced well into the discontinuous possibly leaving their imprint as far as the maximum.ejecta range. This Ray- Valley structure is a key feature of the Schooner ejecta field against which the dimensional (Chapter IV), geomorphic (Chapter V), and geologic (Chapter VI) characteristics are compared. The continuous ejecta field, also called the ejecta blanket, is comprised primarily of material.from the overturned mound sections (flaps) overlain by discrete masses of ejecta that have impacted ballistically. The discontinuous ejecta field is comprised primarily of ballistic impacts together with some material from the ejecta blanket that has moved outward along the ground surface after initial emplacement. Secondary craters, formed by ballistic impacts of ejecta masses, are observed from the crater rim out to maximum ejecta range; but are concentrated between 3 and 6.5 R8 (400 and 850 m). The entire ejecta blanket and much of the discontinuous ejecta field is covered by thin, late-time, fallout deposits from the base surge and cloud. Ejecta sizes are strongly bimodal, consisting of boulder-size blocks up to 9 m.in length and sand-size fines. Blocks are derived from.the upper densely welded tuff unit (0 to 38.7 m) with sizes and shapes varying about the crater radially, and to a lesser extent azimuthally. Blocks retain, to a large degree, their in situ shapes and are usually bounded by joint and foliation surfaces or by new surfaces paralleling these in situ surfaces. There are two notable 4exceptions, secondary craters and their associated secondary ejecta 56 fields and more significantly the rubble zones that make up portions of the rays. In both cases, block sizes are significantly comminuted downward with most in situ surfaces destroyed. In no case were blocks observed joined together as a result of the cratering processes. Fines were derived from the weakly welded tuf f and the upper portion of the nonwelded tuff (38.7 to 4'75 m) and remain a consistent coarse to fine-sand size wherever observed. There are two minor exceptions. A small percentage (less than 12) of fines was shock lithified into light frothy fragments a few centimeters up to one- half meter in size. Another equally small percentage of fines was melted and subsequently cooled to form the thin coating (up to a few centimeters) of fused glass encasing many blocks observed beyond the continuous ejecta boundary. Although portions of the weakly welded tuff were lightly cemented in situ, except for the "c" unit, no cemented ejecta masses were observed in the ejecta field. 3. Dimensional Relationships The dimensional characterization of the Schooner crater and ej ecta field was accomplished by serial stereophotography and photo- grs-etric analysis, details of which are presented in Appendix 31. The resulting isopach map (Fig. 26) was used to generate most of the numbers and profiles presented in this chapter. Table 2 presents dimensions for major features of the Schooner crater and ejecta field. Those dimensions enclosed in parentheses were originally reported by Tune (1970) based on initial work by American Aerial Surveys. 57 TABLE 2 SCHOONER DIMENSIONS FEATURE Apparent Crater Radius (Ra) Apparent Crater Depth (De) Modified Crater Depth (n1) Apparent Lip Radius (Rel) Apparent Lip Height (Hal) True Crater Radius (Rt) True Crater Depth (Dt) Ejecta Lip Height (11.1) True Lip Height (nu) Upthrust Radius (3“) Continuous Block Boundary (Rb) Continuous Ejecta Boundary (Rab) Cavity Radius (Re) Maximum Missile Range (Rm) Apparent Crater Volume (Va) True Crater Volume (Vt) Upthrust Volume (Va) Apparent Lip Volume (V1) P8111)le Volume (Vt) Continuous Ejecta Volume (Vc) *Values in parentheses were reported by Tewes (1970). AVERAGE (m or m3) 129.8 (129.9)* 63.4 (63.4) 1 76.0 146.3 (147.2) 13.1 (13.4) 129.8 155.1 6.4 6.7 304.8 447.5 510.9 46.9 1,745,433 (1,745,433) 3,840,130 383,538 1,895,063 (2,099,032) 2,094,697 1,511,525 RANGE (m or m3) 71-82 125.9-167.0 9.4-18.0 111.6-147.5 2.1-12.2 3.0-8.2 243.8-563.9 381.0-609.6 _>_ 2150 0'4 [.1 '1 l.’ 58 1. Apparent Crater The apparent crater, bounded by the inner "0" contour of the isopach map (Fig. 24), is moderately asymmetric with largest radius and shallowest slope on the southeast and smallest radius and steepest slope on the west. The apparent crater radius gradually increases to a maximum of 147.5 m (142 above the mean of 129.8 m) on the southeast and then gradually decreases to a minimum of 111.6 m (14! below the mean) on the west (Fig. 25). The crater wall dips an average of 65° (range 50° - 80°) on the north and west where it is exposed to a depth of 23 to 30 m and an average of 55° (range 40° - 65°) on the east where it is exposed to a depth of 8 to 15 m. The average dip of the fallback is near 33°; but locally reflects differing concentrations of blocks and fines together with local slump features which continue to develop and change with time. 2. Apparent Lip The apparent lip lies between the inner "0" contour and the maximum ejecta range. The apparent lip radius (R81), measured from SGZ to the crater lip crest, is moderately say-etric ranging j_I-_ 141 about a mean of 146.3 m and closely paralleling ll,l (Fig. 25). The apparent lip height (Hal) is asy-etric ranging from 9.4 to 18.0 m with a mean of 13.1 m and reflects the 11 crests and intervening troughs (Fig. 25). While the primary trends of 11a and Rel are independent of the Ray-Valley structure, secondary perturbations of DJ J ( \ \ ’r \ / \ .13 CINJOH . P4;- «J'JU .~ Dec! V‘y . .( .... ...: r ...eu.z m.-(4U~. II... n. 59 EB _ [ H1011) aovaans (muons 'IVNIDIHO EIAOEIV IHDIHH can as can can 8” 8a 8a 98 o2 8,. 8. 3. on. 8. 8 8 2. 8 o 1 q 4 4 dl J. J q 1 d d a q A d 1 d \/(\/ U s .\ K E wagons oz... 6c memmmo . 1 s8 2 8 3 8 \N 3 one/(oz: :u .3 G C 8 2 3 n 5 3 3 n» «so do 3. r / 1 . \x/I..\/.\ // a n 1 \ \7: / o .. r 1.. l K m . \I \ L\\\ ’1’ AMI . L K} a. if lll/ . I o ../ q T x I / sou—IA mvw \\8 ,\ r / 35” \{K /Em._ 9.1mm \ r cm on surfing mo sown—25m o no usage: mu.— uso 3365— 3.— .esunwm mousse . . . snows-sol:— usousnaz .mu shaman $8.183 masseuse. , S \ H 5’ >L\> 7 1 41 J t1 . U/er <2: /1 L .l/ \ 32.1.4ng ....,//\ /k < . I 35... / _o 1, tuft/k r . :85 93m x . ,, x r I ll \‘1” \I\ 1 an I” \.l \\\ a” s. L .0“ (II \\ .\ a, \s t T IIIIIIIII o I s\ a. \s fl II II II C ’1 \\ ol\.\ t r 0233 .. .. x 33m 1 1 ... E3 9:; r p L r p t P p p P L p p b a b b _ am— an— c: on— on. o: ("a ‘le (In) 2593 NORA: SONVLSICI 60 R‘al 8, 9, and T-S, 7, 8, and 9. appear to line up with some crests and troughs; e.g. C-2*, 6, 7, a. Crests Crests, bound by the inner "O" and approximately the outer 25 ft (7.6 m) contours, are composed of one or more segments of an overturned flap, each roughly semicircular in plan view. When viewed from the ray side, crests appear as a series of irregularly descend- ing plateaus while on the crater side, they slope evenly down to the original ground surface with dips ranging from 20° to 40°. Note that prior to the failure along the hinge zone of the overturned flap, crater-side slopes were probably nearer vertical. While crests are to a first degree similar in detail, they exhibit differences in shape, structure, and geology (see Chapter V. A). Crest peaks occur along the crater lip crest, except C-lO which is displaced over 30 m outward. Crest peaks are usually not symmetrically positioned with respect to the crest. Most crests contain a singularly distinct peak (C-1 and 7); but one is without a peak (C-3), and another is double peaked (C-6). As shown in the Hal plot of Figure 25, Crest 4 contains a poorly developed second peak, Crest 6 contains a poorly developed third peak, and Crest 9 contains a single peak that maintains a near constant elevation over 17° azimuth (~43 m) . In plan view, crest shapes vary from long (with respect to circumference) and narrow (C-ll) to short and wide (C-7). Crest *C-2, R92, T-2, and V-2 are symbols for Crest 2, Ray 2, Trough 2, and Valley 2, respectively. .l-lbl _ ._ . 4 . . .n 61 lengths, measured from trough to trough, range from 41 to 133 m (‘i‘ . 92 m); while widths, measured perpendicular to the length, range from 48 to 88 m (3; - 68 m). Spacing of crests is uneven about the crater varying from 17° to 51°. The inner slopes (towards 862) average 33° for the overlying fines and 40° for the underlying blocks. It is these inner slopes, particularly the fines, which are being slowly eroded into the crater. Outer slopes average less than 10°, but approach 50° to 70° at plateau boundaries. Slopes between crests and troughs range up to 60° depending on the type (fines or blocks) and quantity of ejecta. b. Troughs Troughs, unlike crests, do not contain large concentrations of ej ecta. They are therefore structurally and geologically simpler. They vary in shape from narrow (with respect to circumference) deep features (T-6 and 11) to broad shallow features (T-2) depending upon crest spacing and the degree of "flooding" (downward movement of ejecta) from crests. Trough widths vary from 1/4 to 1/2 that of the bounding crests; while inward and outward slopes are typically 252 and 502 steeper. Crests and troughs differ primarily in the amount of ejecta they contain. Figure 26 presents a plot of the apparent lip height (Hal) and its two components, the upthrust or true lip height (an) and the ej ecta lip height (11.1) obtained from Figure 37 and adjusted for slope of the crater lip. The constant elevation lines are means for crests, troughs, and create and troughs combined. 62 «— n— m— 3 5m .3295 one woods oswsouu. use oououu on 3.3.3: 93 300 «u use .0999 Jeanne: .on snow: steamers EDEN... 8m oz” can 8n 2%. 8a or... on... can 8. 8. 3.— an. 8. 8 as or cm a a; much—OMB Q73. ADV memmmo B C 8 3 so 2. 20 oz. .8 E. G S 3 S. no 2. «u 2. no 2. ecu do 2. .... u E m 3 "E x .. as . c + u. m ..r x., ..r 3 "3+1! m. . ...» n U. x \ ,,.\. ...,, > \ so v.6. x \ l x w L rkx I \ I. \ In :11 / xi/ xv/z a. f I a .I..\ M/ W 1 a; \ v\\/ o I xx 11 as I/ N A s . s a. s .(\ t ........... xv..-) .................. i1. . ..::..... ...... a ............... Mt: W.\ II‘\\ (oak )\\\ (\ Ia» \\\ III/I’d “ml/o(\\lol'lnl|\ It? >‘§( cob F“ I! \‘1‘ . ’ W C Ms I m 4 a 5 .- a \\ t /. :1 rd. / ss / \\ L V L)! )\ I ( \ )p > a. m. a¢\ \ s N . \V 0.0— .175 .XI A/ \z 7 \.4/ \f/ as... > \V r .1 x xx/ x ,4 xx / .. / a < / >. .1 x \x x x 9.2.: +o§ / x x z x \ ..a < , \ «Lx 9. .1 V? /x , ..a (\ a x xx 92 .6; c / \a/ /\ ... < .0: < .0: L a . |-| ..x ._ .... a .II.. 2.: 02m0m... - L L p L p p a L L p n p m p b b (m) HOVJHDS CINflOHD "IVMIDIHO HAOHV .LHDIEH Fm; ‘ tax: .. a ‘ tile {'8' r: 2f: '33? lb La stature 13310-6) 63 While ej ecta and upthrust heights have nearly identical means and both vary about the crater, only ejecta heights reflect the Ray- Valley structure of the lip. In detail, while the upthrust ranges fro. 3.0 n (T-G) to 8.2 n (C-1, 2, and 7), there is little preferen- tial difference between crests and troughs as illustrated by their means (6.6 I vs 6.5 n). Azimuthally, there is slightly greater upthrusting in the southwest through southeast (T-lO counterclockwise to T-B) and slightly less upthrusting in the northeast (C-S to T-6). Ej ecta thicknesses of crests average twice those of troughs. Asinuthally, ejecta increases toward the northeast (C-4 to C-7) and thins toward the south (T-l to 'r-3) and west ('13-9 to T-lO). c. Rays Rays consist of concentrations of ejecta extending from the crater out to the continuous ejecta boundary. Beyond the crest there are typically one or more topographic highs (concentrations of ejecta), a smooth flat area between 1 3/4 and 2 1/2 Ra, and a terminal rubble zone of brecciatsd blocks. Ray 3 is the only ray not containing internediate ej ecta concentrations. Ray 11 contains an isolated ej ecta lass beyond the continuous block boundary. Topo- graphic highs are typically lens shaped in plan view with long axes radially outward, but skewed slightly with respect to SGZ. Ejecta gasses range up to 9 x 103 n2 in area and rise as such as 4.6 1: above the surrounding ejecta blanket. Rays 1, 7 , and 9 are best delineated because their topographic highs are in line with each other, their crest peaks, and SGZ. This .1 64 is not the case‘with other rays where topographic highs do not line up, particularly Rays 5, 8, and 10. Beyond the 25 ft (7.6 m) contour, rays typically slope toward preshot ground surface at less than 5° except in the vicinity of topographic highs where slopes can approach 50° to 70°. d. valleys valleys, beyond 100 n of the crater rim, contain little ejecta that have not been derived froa adjoining rays, either by tulbling of blocks or "flooding" by fines. The alount of flooding ranges fron extensive (V—l and 9) to slight (V511). Valleys are skewed to the degree to which they are flooded from adjoining rays. The axis of each ray and valley has been drawn on the modified isopach nap (Fig. 24). Each axis is skewed to acne extent since no single straight line can adequately represent an entire ray or valley. These skewed axes are obviously not unique; but were drawn as best representing actual field conditions. Each skewed ray axis consists of a straight line fro-.SGZ to the crest peak followed by a mini-um set of straight lines connecting the topographic highs out to the Reb° For Rays 6 and 6 (C-6 has two crest peaks) two axes were required to adequately represent the topography. Sinilarly, Ray 10 required three axes. valley axes were constructed in the sane.nanner except they follow the topographic lows. In this sense, valley axes bound the ejecta ease of the enclosed rays. Of the 15 ray and multiple ray axes, 9 are skewed clockwise (with respect to 862) and 4 are skewed counterclockwise (all on the ll g: 3-3, 3, 13' Valley axes nag of 5°. 1 rated troug'. ”is: for ra E. Area? The 15y: I}: see; in ”‘33 3032011: 2‘ ”395W“: rites: 65 west: R-8, 9, 10L, and 11). Average net skewing is 7°, maximum is 15°. valley axes are evenly skewed to either side with an average skewing of 5°. Note the near-mirror imagery with respect to SGZ of the paired trough axes 11-6, 1-7, and 2-8. Similar relationships do not exist for ray axes. C. Areal Relationships The asymmetries of the apparent crater and lip described above can be seen in plan view. Figure 27 presents traces of selected isopach contours from Figure 24. Each isopach contour is compared to its corresponding mean contour (a circle), constructed such that its circumference is equal to the perimeter of the isopach contour. The difference then is a measure of the asymmetry of the crater or lip at that elevation. l. Apparent Crater The lower oneehalf of the crater, -75 ft contour down to -208 ft contour {-22.9 m.to -63.4 m), is nearly symmetric with only a slight but persistent elongation to the north and a less and varied shortening to the south and southwest. These small perturbations can be attributed to differences in fallback distribution; i.e. the lack of talus trains on the north and broad talus trains on the south and southwest. 0n the other hand, the upper one-half of the crater, -75 ft contour (~22.9 m) up to zero ft contour (l 2.), is asymmetric, being elongated to the east and southeast while shortened to the west. Note that the elongation occurs along the direction of the preshot 3...: see. Fine «:9: nuaav— .. \‘ u‘..\ I a. an . H. . Knee» .fiu-z (: IQ. ...: 2v. ‘3 a. 1. .. 3734}. _. “at“: W: 66 Z announce new: 505. new: announce :Knml v.03. osm— mN mum—HBO 3.2793: eon— O 3. am ass-s! 1 1— 4 d d J E can on. o O + mm mm27: a yum—EDD 3.3— I063 ..oc— Andolnét ...:co ) \ ab: and: \a-r fldDDQVe‘I) noon—00H 3.50.?» no confines-80 Ego—I06“: no: 3m :.9 I92”. ofin G mew: . R one»: .5. 9025. as: zm xeezenm . ...—395 unopened .8 8.52 o.— —.—I a; l v.— ... n.— l o; I a." T ..nv (8w f,OI X) ammo/x T..— 72 Volumes were computed by determining areas between contours with a compensating polar planimeter and multiplying by the appropriate thickness, see Appendix B3 for details. To obtain relative volumes for each ray, lip volumes were divided by their corresponding crater volumes (Fig. 28). The assumption used is that material was ejected from the Schooner crater in a radial manner. Previous workers have shown this to be the case for buried bursts (Sakharov, et al., 1959 and Carlson and Newell, 1970). When normalized in this manner (i.e. V1/Va) Rays 1, 4, and 7 are largest while Rays 3, 8, and 11 are smallest. The greatest enhancement factor is for Ray 1 (1.82) and the smallest enhancenent factor is for Ray 3 (0.73). 2. Ray-Valley Comparisons Volumes of the apparent crater (Va), true crater (Vt), apparent lip (V1), and upthrust (Vu) were computed for each ray and valley from profiles constructed along their respective skewed axes of Figure 24. Profiles for Rays 1 (largest), 3 (downhill), 10C (uphill), and 7 (second largest) are presented in Figure 29. See Appendix B4 for methods used. The true crater volume (Vt) and its two components.apparent volume (Va) and fallback volume (Vf) (where Vf - Vt - a),do not reflect the Ray-Valley structure of the lip (Fig. 30). The true crater volume exhibits generally the same asymmetric pattern about SGZ as Va, both of which follow closely Ra and R31 (Fig. 25). True crater volumes deviate slightly more about their mean than apparent IN. 73 3 use .h .m ..H as: he: now audios." nousuu noun. was soon—seas An: 9N4 20m OMHN ME 20mm HUZSHEQ . an shaman So 2... 3n S... 2: 94 8.. 8.” 3n 8... 8a ox... 3... a: 8. 9.. 8. 3 8 on o r . s- i ...... 2 . H n mu— 1. I .. . J i II .I . ><¢ 8— .. 1 an . on A5: 3.5 3: 2 . 5. 2 5. x 5. 3...: a 5. I! I F — - I - - - .....-i.........i .. - - .. ...,-.. - -..:.. ............ o 111.....mfihm flit: ..... f P L bbbbbb b b r b r D f f ) r trblr P L r D r FL b LIL ? Plrh D!) .P I. Ihlr >>>>>>>>>>>>> a (m) sevasns (muons 'Ivmomo MO'IEIH/KAOHV HONVLSICI 74 shod—ob use mks: you nonsense-50 cause-53> 33 use poncho 302on messes... . on own-mam con 36 can can can con own cum cow 62 _co— 3.. cup co. 8 co 9. on c . a; mmODOMB 92¢ ADV mhmmmo o _ 1 4 q fl q _ J _ _ a _ J _ 4 I4 .11 4 A q _ a mu n... «U m... 00 3. EU a: :U :p —U p... «U uhmu n... 10 V... mu a... «flu .30 \o.._. n I P n 1- I? I) 11.1111E111h1: 9111‘ I1 ..1 _ .. . . .1. 1 .11:.! _ 1.:1.1.:1...1‘1...11...1.1 1.1!... ...V 1 ... .I. a a a .x. ...— 1/1 A3>v|Xu \ 0 ...i .,. . x . .e. x . .3. .. 1 ...“ an .. ~ -- \ a s» a s. \ ’a m. u. l.. > ..‘u .....v .\..\\‘ o l . . , ..., ...... ...,.-. .... .. - . . .... ... . . 2 in. 0V pm. (am 901 x) mn'IOA 75 crater volumes (1 232 vs -_O-_ 162) and there are slight azimuthal shifts in maximum and minimum values. Apparent crater and fallback volumes average 461 and 542 of the true volumes. respectively for both rays and valleys. Only where Vt is a minimum (T-6 to C-lO) does Va - Vf; elsewhere, Vf > V . Apparent lip and ej ecta volumes, on the other hand, do reflect the Ray-Valley structure (Fig. 30). The upthrust volume comprises 202 of the apparent lip volume and remains relatively constant (+ 202 to - 282 about the mean). This is a direct conse- quence of the relatively constant upthrust observed along the crater lip (Fig. 26) and the assumed uplift profile. Ejecta volume makes up 851 and 661 of the apparent lip volume for rays and valleys, respectively. It is this ejecta volume (Ve - V1 - V“), varying + 1222 (R-l) to -812 (V-ll) about its mean, that is responsible for the relief of the ejecta blanket. Thus, ejecta-lip asynetries ~observed along the crater rim (Fig. 26) are continued outward over the ejecta blanket as ejecta-«ohms asynetries (Fig. 30). 3. Ray 1 Variations Ray 1, from the V-l axis (153°) clockwise to the V-ll axis (194°), was examined in detail by constructing radial profiles in one- degree increments from SGZ out to the Rb. Volume calculations were made for 360° with the computer routine discussed in Appendix B4. Apparent crater volumes (Vg) and apparent lip volumes (V1) are shown in Figure 31. V. is independent of the Ray 1 structure, gradually increasing from V-ll (194 ) to V-l (153°) following a pattern similar q~C\ so... 76 .n >3— mmouo< mason—onus common use 5 museum mama—com you mosses.» a: one season uses-284 .Hn ensues 38..me census... «2 Q: on. on. on. no. 3— 3— mo- 0: a: v: c: a: on. mm. 92 02 3— 2: no— vo— J 1 d e u A d 1 a) q a fi 4 d a — q u l4 « q d \\ T p111 L r ..> 1 . L I J T l 1 _. L _ _ a _ . . L _ L r F p T p p _ _ . . . . co on— on— cm— o—n ova aha can can com com Gav (8m i,O'IC X) EIWH'IOA 77 to Ra (Fig. 25). The apparent lip volume (V1) reflects the Ray 1 structure, rising from 194° to 183°. Fro-.183° to 153° the lip volume gradually decreases. This gradual and lower net decrease reflects the flooding of ejecta from Rel into V-l, whereas V-ll is relatively devoid of ejecta. 4. Cumulative Distributions Cumulative distributions of V1, Va, and Vu as a function of distance from SGZ for Ray 9 and Valley 1 axes are presented in Figure 32. Volumes were computed by revolving skewed profiles through a onerdegree arc and agree within 22 of the volumes computed by the previously discussed area moment technique. Uplift volume is distributed close to the crater where for both R99 and V-1, 502 and 902 of the volume is located within 1.4 and 2.0 Ra' Contrast this to the distribution of Va, where 502 and 902 of the volume is at 2.2 and 3.2 Rll for R99 and 2.0 and 3.1 Ra for V-l. Figure 33 compares cumulative distributions of Ve for R99 (a large volume ray), V-l (a flooded valley), Rel (the largest volume ray), R23 (the smallest volume ray), and V511 (a valley with very little ejecta). In each case, the distribution of the majority of the ejecta (between cumulative 202 and 802) is a strong function of the total ejecta volume present; i.e. the larger the total volume the farther away from the crater it is distributed. Distribution of the far-out ejecta is not a strong function of the total ejecta :volume. v,(v. n 78 New Bonn Gunman:— uo nuance—fl e as .n head; use a as: new §Ho> sous—nu moo—53:00 use Josh—nun: .93 no seamen—«mung .3 one»: As: NUm 20mm MUZ was mean nouoouom now now some vacuumwe mo souuocsm a mo mssuo> muoofim msossuusou mo cowusauuuoun AcuvnfiumHanwmanESSHmru coo can can can 03 on” can on" com on — cc— .mm «names \ n11 :I> ..I> d on on as oo— (mamad) awn'IoA amivmwno 1X .1"! I! h u. CHAPTERV GMRPHIC CHARACTERISTICS OF THE CRATER All!) CONTINUOUS EJECTA FIELD .A. General Although used in extraterrestrial studies, geomorphic mapping of terrestrial craters and ejects fields has received little attention by investigators. nonetheless, such a study is ideally suited for Schooner because of its distinctive and varied set of surface features. The ejecta field exhibits an inverted stratigraphic order with fines from the weakly welded and nonwelded tuffs overlying blocks from the upper densely welded tuff. In the crater, on the other band, fall- back exhibits a complex, but apparently normal stratigraphic order with blocks overlying fines. The initial distribution of blocks and fines followed by post-depositional movement gives rise to a large variation of surface morphologies (Fig. 21) which for this study have been grouped into seven distinct regimes: blocky, rubble, smooth, drowned, hu-ocky, mixed, and transitional. Appendix C presents a description of the morphological regimes and discusses procedures used in their *mapping. Over 550 separate areas were required to map the crater and continuous ejecta field. The data accumulated are listed in Table C1 and presented in three geomorphic maps: a surface feature map, a ‘block size map, and a block areal density map. Maps are provided in the map pocket and reduced to page size in Figures 34, 35, and 36. 80 21K 11'!“ “1 I1 .I' 1 I :3 . HQ 81 GED-ORPHIC CMTER AND WI IA? SURFACE FEATURE! .O‘V-WS “(cu WV ONVINUCU! [1! EVA IOUHMIV IIIID anus CIA". I‘LL GONVWUOUS ILOOI IOWDINV Figure 34. Geomorphic Crater and Ejecta Map - Surface Features at". cum I 51:4 w m '52! NI .. .0 14m W. thsb:h c K a. , .1 ..m. M an. 51. 82 Figure 35. Geomorphic Crater and Ejecta Hap - Block Size I'll” an C’J'El 1| 120 kit. 16" . .. .. __ . i, 1‘1 .. .3 .. 7...... ... .. a £11.... , . . e xiv . P . 1\\ Na mu I 1 a... VI . . .~; / . . ......)A}... x x.) .U .. (1.6.. . ...”...K. . .VV . HERE 2 \D .... ..0L-..1.It$\xx.vx . We «5 x .. he..." a...» .v N. a .e. b... 83 vtmr men - mew - tum-tours - M :1 runs I: cum wsu. - Figure 36. Geomorphic Crater and Ejecta Map - Block Areal Density ' gym: Crater 1. Surface 1 f2 ufor fe h overrun lisdivided 1 111311131. 3311 1 33th: of bloc] 3 900th 1 Emmimums . hi! ranges up 15141! CIests aiming 310v 1 711': the era 84 B. Apparent Crater 1. Surface Morphology The major features of the crater from the rim crest down are the overturned ejecta flap, the soil horizon, the wall, the fallback, and the floor (Fig. 34). a. Overturned Ejecta Flap The overturned ejecta flap, exposed below the crater rim crest, is divided into a smooth area consisting of fines from the weakly welded and nonwelded tuffs underlain by a blocky area consisting of blocks from the upper densely welded ruff. The smooth area 01:1-7, Geomorphic Mapping Units 1 thru 7) is not continuous about the crater, being confined only to crests where it ranges up to 2.7 m in thickness. Crests 5 and 10 contain no fines while Crests 3 and 4 contain only scattered amounts. This area is undergoing slow, but continual erosion (up to 1 m between 1969 and 1974) with the eroded material transported down into the crater. Detonation of the Randley event, a 1.2 HT buried event with a slant range of 5.5 km to the southeast, caused a number of circumferential cracks 1 to 6 m out from the crater rim which have accelerated the wearing back process (Shackelford, 1971). The blocky area (14:8) is continuous about the crater ranging up to 12 m in thickness. There have been no large slope failures, except on the south; but there has been a continual movement of individual blocks into the crater. A typical blocky talus train on the northeast (14:61) is carrying blocks from this area into the crater. b ‘5 .. 7 l. 1‘ . . .5 1 H ). Soi infirm; "’5 ‘33: ::a ”lei :u: 3.5 frag ' 5 feta: x" . ‘11”. K. g» \ \2 .-_ NI 85 b. Soil Horizon The soil horizon (H:9-l4), consisting of in situ and over- turned components, marks-the present location of the uplifted ground surface. It decreases in thickness from a maximum of 3.5 m on the east to near zero on the west and southwest. On the east (M:lO) where thickest, it is slowly eroding into the crater, e.g. fine talus train 11:51. c. Hall The wall (M340, 60, and 87), consisting of the uplifted and blast-fractured upper densely welded tuff, is exposed continuously about the crater except where covered by fallback. weakly welded and nonwelded tuffs are not exposed along the crater wall. wall thickness ranges from 7 to 15 m.ou the east and 15 to 23 m.ou the west. Only ‘minor degradation of the wall has occurred since crater formation. d. Fallback Fallback, including material eroded postshot from above, consists of blocks and fines distributed continuously from where it overlaps the crater wall down to the crater floor. Morphologic regimes include blocky, smooth, and mixed areas. Rubble areas are not identified; but broken blocks contribute to both the blocky and mixed areas. Because fines do not in general cover blocks, neither drowned nor hummocky areas are present. The distribution of morphologic units, while controlled primarily by the shape of the crater, also reflect the Ray-Valley structure of the lip; e.g. portions of the crater rim that failed during overturning, material eroded postshot 1. IE’ .~ :1 1537: rm 9...: :1: Black? :::.: fail: :erk 1 rs. firs. :11 m: i"; ad 1 tr; of : IL 29:: -‘ I 5.3-? in 86 from above units, and the distribution of the large smooth areas containing the weakly welded and nonwelded outcrops. Blocky areas dominate almost down to the - 100 ft (-30.4 m) contour while smooth areas dominate below. Overall, the distribution of fallback reflects a normal stratigraphic order with blocks over- lying fines. There are exceptions, one on the east where fines locally overlie blocks (Mz41, 43, and 45), another on the southwest (n:112 and 128). While blocks are observed overriding the peri- menters of the five smooth areas (Mo47, 67, 80, 84, and 125), few blocks cross the interiors apparently due to the slight outward bulging (toward the ZP axis) of these areas. Pine unit outcrops (M:46, 71, 94, 130, etc.) discussed in Chapter VI. C are contained within these smooth areas. The large smooth area on the east (Hz47) is aligned with Crests 3, 4, and 5 which contain few fines. Similarly, the smooth area on the southwest (H1125) is aligned with Crests 10 and 11 which are also deficient in fines. The smooth areas, particularly the outcrops, are slowly being eroded with the detritus washing down the crater and onto the floor. This distributional pattern of blocks and fines is modified by a number of talus and slump structures. On the south, a large slump structure extends from near the crater rim.down to the floor and consists of a mixture of blocks and fines (H:17-29). Other slump structures exist on the west (M:104, 106, 108) and north (H368 and 69). On the east (M:55) and northeast (H:6l) small talus trains are forming near the rim. Trenching operations in 1969 are probably 87 responsible for the mixed zone on the south. Where fallback begins along the wall, there is co-only a 1 to 6 m wide band of fines (11:36, 75, 88) presently accumulating from erosion of the overturned fine ejecta units in the flap. The Bandley event probably accelerated the growth of these features. e. Floor The nearly circular floor (11:27) is clearly anomalous. It is shifted to the northwest with respect to SGZ reflecting encroachment from the east and south. The floor contrasts sharply with the fall- back in composition and morphology. Its surface has many of the characteristics of a plays; i.e. flatness, dissection cracks, very fine grain composition, and complete lack of blocks (except those that have obviously rolled or slumped on at post-crater times) . Probing has shown that the thickness of the floor unit at scz' is at least a m with composition and grain size unchanged from the surface down (Day, 1972) . There has been a slow, but apparently continuing encroachment of fallback onto the crater floor. The floor is covered by a thin sheet (2 to 10 cm) of fines washed out of the fine outcrops above. Centimeter-size shocked pmice fragments, washed and rolled down the crater, thinly cover outer portions of the floor. Coarser fragments (up to ll 3 m) are collecting at two cresant shaped ridges on the west and northwest perimeter. On the west there are two talus trains 01:106), 3 to 6 m wide by 1.5 m high and composed of mixed blocks and fines, that have moved over 8 m out onto the floor. On the south a large irregular mass (14:26) 30 m across and 3 m high has moved 9 m ‘43.“?! $391100? 1m: 72516 3 a zimr 31‘ a: the I; the la mafia *wke 88 onto the floor. A number of large blocks, one 9 x 6 x 6 m (M:l34), another 6 x 6 x 6 m 01:10), and several smaller ones on the northeast have tumbled onto the floor; again all postshot. The two equi-dimensional blocks on the northwest portion of the floor (M:107) tumbled there during the Handley event. Observation of their impact craters indicates that in 5 years (1969 to 1974) infilling of the crater floor has been less than 15 cm. 2. Block Size The size distribution of blocks in the wall and the over- turned ejecta flap is discussed in Chapter VI. A. The size distribution of blocks in the fallback is controlled primarily by the shape of the crater with block size increasing down- ward (Fig. 35). This pattern is modified by talus trains and slump features. Transportation of blocks down the crater via talus trains locally decreases block size in the blocky areas (14:30) and increases block size in the smooth areas (leO6). Slump features produce a similar effect, but in a more complex manner since they involve a larger percentage of fines and some mixing of blocks and fines 01:24-26). The relatively larger block sizes on the east side of the crater are due to a combination of factors, including fewer fines in the overturned flap, more postshot slope failures along the crater rim, and probably larger in situ block sizes. I'- _a I | I- ‘— 3‘4 . ‘- V 3. Block Block area 722.7901‘ the l 89 3. Block Areal Density Block areal density, like block size, is primarily controlled by shape of the crater modified by talus trains and slump features (Fig. 36). Block areal density is obviously high in the blocky areas and decreases sharply with the onset of the smooth areas. Areal density for the mixed areas is intermediate. As a consequence, talus trains and slump features generally reduce block areal density above the -100 ft (-30 m) contour (11:51) and increase areal density below (14:70). C. Continuous Ejecta Field 1. Surface Horphology The general spatial distribution of blocks and fines in the continuous ejecta field closely reflects the Ray-Valley structure of the lip. Wherever blocks and fines are observed, they exhibit an inverted stratigraphic order (fines over blocks) with little evidence of mixing. The only exception is where secondary cratering has destroyed this order by inverting the order once again. In general, blocky areas are observed where fines are thin, primarily along ray perimeters and in partially drowned troughs and connecting valleys. Within ray interiors blocky areas are observed along most topographic breaks. Rubble areas are concentrated at ray termini, but are also associated with several of the topographic highs (flap segments) within rays. With few exceptions, fines cover all block and rubble areas to some degree; but are concentrated in the central portions of rays where they formed extensive smooth areas. 1. 310: Elects a :1. 31:15:: I :21 areas 01 1:32:55 :1: ‘41! were retiag val vs no .4 90 a. Blocky Areas Blocks are best exposed along ray perimeters where fines are thin. Blocks are concentrated at ray termini where they surround rubble areas on the outer three sides. Blocks underlie all crests and troughs along the crater edge (Chapter VI. A) and are only lightly covered by fines in several troughs (T-S, 6, 7, and 11) and connecting valleys. In ray interiors, blocks are exposed wherever there is a sharp topographic break; e.g. crest plateau boundaries (M:388, 395, and 505), steep slopes bounding crests (11:251. 385, and 499), and between most crests and troughs (M:212, 293, and 397). Blocks are also exposed along many topographic highs; e.g. R-4 (11:241), R-S (11:256, 278, and 283), R-6 (11:301-303), and R—lO (M:409). Although blocks are observed seemingly wherever fines are thin, blocks are not deposited continuously from the crater rim out to the continuous block boundary. Examination of the trench (Chapter VI. B) indicates that while blocks provide the foundation for Ray 1, there is at least one interval, 250 to 300 m (2 to 2 1”: R8), where there are no blocks. This location in the trench coincides with portions of the smooth area of Ray 1 (11:162) which in turn is aligned with an almost continuous circumferential band of smooth areas distributed around the crater. A number of other locations along this circumferential band provide further evidence for a discontinuous deposition of blocks. At the excavation surrounding drill hole P11 #2 (It-8, 11:394) very few Em J5; are obs :1 ate: n} nation of m: and 3 2 1:1 of a :m of 11: 913102 1": 311351: “Salad 1 121; H, a “£1on 91 blocks are observed. Also, at several locations where fines from rays enter valleys, field examination indicates a discontinuous deposition of blocks; e.g. R-l (1!:529) and R—ll (11:496). Thus the symmetry and persistence of this circumferential band argues that the lack of a continuous layer of blocks is a basic depositional feature of the Schooner ejecta blanket. Horphology of the blocky areas suggests movement of ej ecta after deposition. The outward spreading pattern of many ray termini accompanied by broad protruding masses (R-l, 11:534 and 536; R-4 11:224; R-8, 3:369; and R—9 11:415) points to both forward and lateral movement of ejecta on the ground. Along the leading edge of ray perimeters, there are numerous small blocky lobes which protrude up to 5 m beyond the average boundary; e.g. on R-2 (14:179), R-7 (1!:313), and R-ll (1!:518). Along lateral ray perimeters, similar blocky lobes are present, skewed from perpendicular to the perimeter to radially outward from the crater; e.g. on ll-l (11:530), R-2 (1!:179), and R-ll (H:486) . Tinally, most troughs and connecting valleys contain accmlations of blocks that have obviously tumbled down from surrounding crests and connecting rays. In cross section many of the ray termini contain low areas 10 to 30 meters behind the leading ray perimeters. Outward the surface is typically "stair-stepped"; i.e. the surface rises gradually for l to 2 meters and then drops off quickly. This "stair-step" is repeated several times with the net surface sloping gradually down to the original ground surface. "Stair-steps" are not well developed, if so be 92 they exist at all, along lateral ray perimeters. b. Rubble Areas Rubble areas are associated with four physiographic features: ray termini, outer ray segments, interior topographic highs, and isolated masses near the continuous ejecta boundary. With depth some rubble, actually broken blocks, are observed beneath crests and troughs (Chapter VI. A). Rubble areas are observed locally within flap segments along the trench (Chapter VI. B) where they tend to be localized and surrounded by unbrecciated blocks. With distance from the crater, brecciation increases. Rubble areas are observed neither along ray perimeters nor on the surfaces of crests, troughs, or valleys. The largest concentra- tions of rubble are observed near ray termini where they are surrounded by blocks on the outer three sides and overlapped by fines, the hum-ocky areas, on the interior side. In plan view rubble areas follow the general pattern of rays ranging up to 2 x 10" m2 in area. In cross section rubble areas typically consist of a broad topographic high rising 1.5 to 4 m above the surrounding ejecta blanket followed outward by a broad shallow area that is often slightly depressed below the surrounding ej ecta blanket. Rubble areas typically occupy major portions of ray termini particularly those containing large outward protrusions (R—l, 4, 7, 9, and 11). On Ray 1 there are three terminal rubble areas, two associated with protrusions (11531-533 and 11:172-174) and one not (11:164). Along portions of R-lO, there is a band of rubble roughly ::j S! as! ::L‘tatlv 9:11! f1 3:. he 93 paralleling the ray perimeter (M:424-426, 458-460, and 464), while along the eastern side of the ejecta blanket there appears to be significantly less rubble. The extent to which rubble areas are covered by fines is a question that only further excavation can answer. The trench shows that two of the rubble areas on R-l (H:164 and 541) are not connected. Rubble areas are observed within the outermost segments of Rays 2, 6, 10, and 11. These are similar to terminal rubble areas; but smaller in area. They contain interior hummocky areas (M:182, 268, 476, and 521) indicating that the fines and blocks traveled together in inverted stratigraphic order with little mixing on or after impact. Rubble are also observed on top of several topographic highs within ray interiors; e.g. R-l (11:160), R-S (11:259), R-7 (M:327), Rr9 (H:405), and R910 (M:455). This rubble is smaller in size than in the terminal rubble areas, at least in part due to a difference in lithology; i.e. "P80" mapping units rather than "RUL" mapping units (see Fig. 51). Study of the trench (Chapter VI. B) suggests that some of these topographic-high rubble areas may be only the "tip of the iceberg" of larger rubble masses below; but excavation is required to substantiate this. A number of isolated masses, up to 103 m2 in area and located predominately beyond the continuous block boundary, are composed primarily of rubble. These rubble masses range from broad shallow sheets (11:169, 171, 323, and 463) to small compact mounds (11:167. 310, .. 9' n): A 1321}. T 1' 512513 a imsit 11'; but, fled if sear-1:1 “In-101 ~.“be' ' g 94 and 321). The former have mixed slightly on and/or after impact. Their freshness and lack of coverage by fines is indicative of late time deposition. Similar features may well exist closer to the crater; but, if so, are fcovered by fines. The distribution and localization of rubble areas indicates that they were formed by brecciation upon impact, although later- stage secondary cratering undoubtedly contributed to further local brecciation. Rubble areas are concentrated within the thicker portions of large ejecta masses (segments) surrounded by blocks that are not brecciated. Since segments probably impacted as a unit, this suggests that the size of the impacting mass together with its impact velocity are important parameters in the brecciation process. Follow- ing this line of argument, the isolated rubble mounds, being relatively small in mass, probably impacted at higher velocities than the larger flap-segment rubble areas. In this sense, the mounds are intermediate to flap segments and secondary craters. c. Smooth Areas Fines cover the surface of the ejecta field continuously from the crater rim out to the continuous ejecta boundary. Scattered patches of fines observed beyond the continuous ej ecta boundary are mostly remnants of base surge and cloud deposits. The spatial distribution of smooth areas and their relationships to blocky areas strongly suggests movement of fines after initial deposition. Overall, fines and resulting smooth and drowned areas are shifted to the east and northeast (R-4, 5, and 6) resulting in xifl‘gm 4:” gas-ed 1104 21:11 dens :fm'a area triad; c ...:.z 11 1?st "‘1 was on 95 increased drowning (Fig. 34) and subsequent decrease in block size and areal density (Fig. 35 and 36). Note that there is a sparsity of smooth areas along the southeast side of the ejecta blanket, particularly on Ray 3. Fines cap most of the crests and spill into neighboring troughs and connecting valleys resulting in varying degrees of "drowning"; e.g. T-l, 2, 3, 10. Fines are thin and dis- continuous on Crests 3, 4, 5, and 10. Fines are concentrated within rays reaching their maximum extent and thickness in the middle interiors and aligned with the previously discussed circumferential band of smooth areas. The largest smooth areas (up to 5 x 10" m2) are located on R—l (M:162), R-4 (11:243), R-6 and 7 (M:299), R-9 (M:394), and R-ll 04:451). As observed in the trench fines fill in and smooth out the topographic irregularities of the underlying block deposits. Topographic highs (flap segments) are drowned by fines to varying degrees from complete burial as observed in the trench, to partial burial (ll-6, 11:301-303), to slight burial (ll-7, 11:327). Two of the largest topographic highs, R-4 (11:241) and 91-9 (M:404-406) appear to have deflected fines to either side. Where fines lightly cover rubble areas, hummocky areas are formed; e.g. R-l (11:539 and 548), R—4 (1!:231), R-9 (11:408), R-lO (11:427), and R-ll (11:492). Fines thin rapidly toward ray perimeters with very little extending beyond. There are several exceptions, one along the middle of R-l (near the trench) where a tongue of fines passes between two rubble areas. Other exceptions are on R-6, 7, 8, E 363951 1 $13.11.? 0 i‘fl: M \- 9:19,: 96 and 9. In each case fine deposits appear to have flowed through gaps between earlier block deposits. Valleys apparently received the bulk of their fines, not from spilling out across the ray perimeters, but by flowing out through such gaps in the ray perimeters, chiefly along the circumferential band between 2 and 2 1/2 Ra° On some of the larger rays, fines apparently overwhelmed these gaps and drowned the neighboring valleys; e.g. (R-l into V-l, R-4 into V-4, R-7 into V-6, R-9 into V-8 and 9, and R-ll into V-ll). 2. Block Size Block sizes on the surface of the ejecta blanket follow the Ray-Valley structure of the apparent lip (Fig. 35). Radially, block size decreases rapidly from the crater out to near the continuous block boundary. Beyond, the decrease is more gradual to the continu- ous ejecta boundary. The exceptions to this trend are in the various rubble areas where a local decrease in block size occurs due to more brecciation and betwaen the continuous block and ej ecta boundaries where local increases occur due to less brecciation. Azimuthally, the largest blocks are exposed in the troughs, connecting valleys, and along ray perimeters. While maximum block sizes in the trench are comparable to those along ray boundaries at the same distances, the amount of brecciation in the trench is greater. Thus, while the observed smaller block sizes on rays is due in part to coverage by fines, there appears to be a basic difference in the mechanisms of deposition and perhaps post-depositional .94 Oh". no: see to with : mate: the z :1 less 511 1:: be 3113‘. idler obse: 31‘ i. sin: ' Jaserved 8:132: of F {it far "P3 3154;“ at 3:11; 202), ‘1“- 1'311 110 t 3 . ~ 31:5 dif ‘3‘ 055; .hs'Q “‘41 as C 97 movement within a ray segment. This difference may reflect the degree to which a flap segment is dispersed prior to impact; i.e. the greater the dispersion the less mass impacting per unit area and the less brecciation. In addition to these Ray-Valley related patterns, block sizes tend to be slightly larger on the east (R-4 thru V-S) which corresponds to similar observations of the fallback and is probably related to larger in situ block sizes. Observed block size is strongly affected by lithology. Comparison of Figures 35 and 51 shows that average block size is smaller for "P130" than "RUL" units. Examples, with PBO areas listed first are: R—l (1!:540 vs 537), R-Z (M:184 vs 185), R—3 (11:201 vs 202), R-4 (H:236 vs 237), and R-9 (M:409 vs 410). The reason that block sizes are smaller on rays versus valleys is in part due to such differences in block composition; e. g. 01-3 vs V-2 and V-3). The observed block size is also affected by drowning from fines. Initially, as drowning begins, the smaller blocks are preferentially covered and average size increases; but later, as drowning continues, the larger blocks are covered and average size decreases. In some cases, there is a clear increase in size; e.g. R-6 (11:306) and R-l (M:545). More typically, size decreases; e.g. V-7 (11:348) and V-lO (11:443) . The larger block sizes on R-3 (11:212 or 201) relative to R—l (M:162) or R-7 (11:299) are due to the lack of fines on R-3. ‘ . £31101! 1 :11 (”3E1") 53:11; patter :::ih ow Sleek : s. \l:. , a}: d 5‘3.“ 5‘31 \. “a 98 An example of both lithology and drowning affecting block size distribution is observed on the outer ray segment of R-2 where large blocks ("RUL"), small blocks ("PBO"), and fines were deposited in an off-lap pattern to the east. A similar example in the opposite direction occurs on the outer ray segment of Roll. Block size distribution is also affected by preshot topography. In the stream cut to the east of SGZ, block size at the bottom of the cut (11:262) is larger than block size on either side (11:261, 2888, 263, and 264) apparently due to preferential rolling and tumbling of the larger blocks down the hill; but not up the other side. An example of block movement downhill is observed outward from R—4 (H:224 and 226) where blocks are spread downhill beyond the continuous block boundary for several hundred meters. This is in contrast to the west (uphill) where there is an abrupt drop off at the continuous block boundary. 3. Block Areal Density Block areal density follows the Ray-Valley structure of the apparent lip (Fig. 36). Areal density is primarily a reflection of the amount of drowning by fines; i.e. areal density decreases with increased drowning. Areal density is highest in the undrowned troughs; e.g. T-S (M:247), T-7 (11:343), and T-ll (11506) as well as in rubble areas near ray perimeters R-l (M:532 and 172), R-2 (M:186), R-4 (11:237), R-7 (11:315), R-9 (14:410), R-lO (11:424 and 464), and R-ll (H:490) . Local rubble areas also exhibit high areal densities; e.g. R-l (11:167), V-3 (1!:225), V-7 (11:321), and V-ll (11:511). he prev: gzwtieast (1 :hrase in 2:55 of f i 11:13 bla: :11 :evered 1‘1: cat frc teal d1 “31? new :::.fz: side 1'73 than av 333931 lack 99 The previously mentioned general shift of fines to the east and northeast (R95 and 6) is noticeably reflected by the correspond- ing decrease in areal density. Field observations indicate that the thickness of fines is not necessarily greater than on other parts of the ejecta blanket as shown by several low flap segments that are barely covered (H3260, 278, and 303). However, fines are distributed further out from SGZ (M:307 and 309). Areal density also reflects the preshot topography. In the previously mentioned stream cut (M:262) areal density is higher than on either side. Outward from R94 (M:224 and 226) areal density is higher than average due to downhill tumbling of blocks coupled with a general lack of fines. "F 0 am; If ’4’ 5307:3131 this settio: 111,151: of :1. 113131195 betv mm lip :10 1 '5! Processes 359 51013 the Win 560mm“ W with m ”5* Wins. 1.3m °f the I ‘3'“! 11mm M imlved. 1' 0"w: r“ trite “1k ate the CHAPTER.VI GEOLOGIC CHARACTERISTICS OF THE CRATER AND CONTINUOUS EJECTA FIELD This section presents the results from detailed geologic mapping and analysis of the crater and continuous ej ecta field. Geologic relationships between in situ units in the wall and ejecta units in the crater lip show that the material in the lip was overturned and that the processes of overturning were orderly. Comparison of the geology along the trench excavation to that of the surrounding ej ecta blanket demonstrates the inverted stratigraphic order of the ej ecta blanket. With these first order relationships as a base line, detailed mapping, analysis, and comparison of the stratigraphy and structure of the crater, crater lip, trench, and ej ecta blanket surface provides a means for understanding the crater and ej ecta process involved . A. Geology of the Crater Lip 1. Overview The crater lip, exposed in near cross section inside and below the crater rim, was mapped in detail. The major features above the fallback are the wall, the soil horizon, and the overturned ejecta flap. Where exposed, the wall provides a good 3-dimensional strati- graphic and structural record of the in situ geology that compliments 100 311111113 115 Edition, the :mfihs hma mhmfi zefttei. Si he 12': littl “it maple: “'3 o 3...} ”3‘5 Km 71» 11,, ad t t "J 51> ‘ 101 the drilling and geophysical logging data discussed in Chapter II. In addition, the wall provides an imprint of the cratering processes in terms of blast-induced fracturing and displacement. The ejecta flap lies above the wall and contains the material originally inside the wall that was compressed, fractured, bulked, and ejected. Since at the crater lip the ejecta was overturned en mass with little post-depositional movement, it contains the simplest yet most complete record of the stratigraphic units comprising the ejecta blanket. The soil horizon lies between the wall and the ejecta flap and thus contains the hinge line along which overturning occurred. Marking the preshot ground surface, its present position is a measure of the net upthrust (upthrust followed by some relaxation) resulting from the Schooner detonation. 2. Mapping Procedures Mapping control was established with 40 stations spaced approximately every 25 m along the crater rim and surveyed vertically to i 0.15 m and horizontally to 1: 0.3 m. Photographs (35 mm color slides) were taken of each station from the opposite side of the crater. From this distance of approximately 300 m, the field of view, centered on a 2 m stadia rod at the prime station, included the stations to either side. A base map delineating major features was produced for each of the 40 stations (L:l thru 40) by projecting the slides at a scale of 1 cm - 2.4 m and mapping the center one-third. Each mapping unit m; ‘. ,‘ A: ‘1‘13‘; '1" in :1 in a re; 231:2: 1'12 11;: died a fusing uni iatian of 21:10:19 ( s. 1 ~41? Kent: 6. an H ‘11.: ‘teu.7 ‘4 . who. 102 ("t" and "v" included with "g") was recorded. Individual blocks were mapped in a representative manner with only the larger blocks along the crater rim mapped 1:1. Base maps were checked in the field and details added as required. Boundaries are accurate to within 1/2 m for mapping units "P" thru "p". Due to inaccessibility, field confirmation of the other units ("3" thru "L") was limited to visual observation from the crater rim, the crater floor, and from along one rope into the crater below L:2. Boundaries for these units are probably accurate to within 1 m. The resultant Geologic Map of the Crater Lip, compiled with the above survey control, is provided in the map pocket and a generalized map is presented in Figure 37. An enlarged photograph of a portion of Crest 9 is presented in Figure 38 and selected photographs of other sections of the crater lip are presented in Figure 39. 3. Wall a. Stratigraphy Mapping units down through most of the "L" unit (~27 m) are exposed along portions of the crater wall. The "P" unit is not identified, but is probably just barely covered by fallback beneath L:31. The ”M" unit can be positively identified (color and texture) intermittently on the west (L:27-37); but must be present throughout the crater since it is observed everywhere along the crater lip and in the ejecta field. Where identified, it ranges from 1.2 to 1.8 m in thickness. The contact betwaen the "U" and "L" units is based _ m.‘ l :53: a3: a ...-time... I ILL: :55. a... I u.mm-m.eu 3.31: Rune ciao Amt—WRI- ...-2. sa> foamed-V so» 3 egg neuouu emu mo as: uwwoaoou nonuaouemeu .sn ouswum meme ml ! memos ____ __lr _ é , 1 ___ 55E?jgea__;§Laaaaggs;ssaz?a=_ ,_ . .4_..__. O. 351». L3 104 “hush! 5 an O. as.oc.oc ..- 9mg m.- .hn shaman .953! main. :1...— $1340 ELIE: .231: m on m I :7...“ 533. Set mflu lu- e.ou-o $th ..::.. E; 7.12.345 ...8 a!» Emma 0553 Blik“ 3:0 I. . . ya 1" I. .‘u '0. 1%..911 IIII‘ . . .1uufl t woumuwooH mafia: unions: cu“: a :95 mo moauuom m. mo :emmwOuosm .wm shaman mNuWH 0.....: Gang ., ., .. turx . t .lqlflwtlflumillh nu} .Iflbfllrahrtallllbh ," fitmlwli.W~ . . . .. 106 SCAL E AT STATIONS 0 ‘00 200Mflers [JellllllllllllleUJ Figure 39. Selected Photographs of the Crater Lip with Lip Stations and Crests Indicated 107 primarily on the higher degree of fracturing for the "U" unit. In addition, the color of the "U" unit varies from red to purple-gray whereas the "L" unit is a consistent medium gray. Due to poor color contrast and sparsity of fracturing, the contact between the "O" and "L” units beneath L:9-ll is in question. The upper portion of the "R" unit is easily identified by its dark brick red color on the east changing to pale red on the south and north and by its ever present white caliche coating. With depth the "R" unit grades into the ”U" unit with the contact often difficult to pick. Local variations in thickness of the "R" unit are usually at the expense of the "D” unit; e.g. on the west-northwest (L:29-30) the ”B" unit doubles its thickness over an 18 m stretch while the thick- ness of the "R + D" unit remains nearly constant. While units exposed in the wall are continuous (with the . possible exception of "11") , they exhibit considerable variation in thickness about the crater. Figure 40 presents thickness of in situ units in the crater wall below each of the create and troughs. As expected, thicknesses are independent of the Crest-Trough structure of the crater lip with azimuthal trends different for each of the units; i.e. ”D" thickens to the north (C—7 to T-6), R to the west (0911 to 'r-lo), and "s" to the east (c-6 to c-S). The range in thickness for the ”R" and "D" units approaches 1 502 about their respective means, while for the "R + D'f unit the variation is near 1 201. The latter is similar to variations observed for the "R" + "D" unit in the four satellite drill holes of DZOu (Fig. 8). 108 com 03” can cu can a... 0U can fine: ~3qu 05 a.“ season—Juana. 3s: mounds: 3am om assumes. EDEN... com . ova emu 8N o2 oo— cv— on. a; mmODOMH DZ< ADV mfimmflO 2. Eu 2» :u _E 5:. ‘1 ommm>ou and I o 2; I :6 and I and serum 4 A...» nan¥U.I.—. ...-23 Oz.tk(1 «U a... mu m... 23¢... 8— on 00 .oe ensue» 9. ON vU 3. «U n... moU Jou ( m) SSEINXOIHJ. SAILV'IIIWHO 109 These circumferential variations in thickness, color, and texture obviously inply corresponding radial variations which have important implication in interpreting ej ecta composition observed in the field; i.e. in determining whether changes in ejecta coeposition are the result of in situ conditions or crater and ejecta processes. b. Structure No faulting, folding, or other significant structural discontinuities in the in situ geology were observed. Each of the welded units is well jointed with all joints near vertical. The "L" unit exhibits hexagonal jointing with columns 5 to 10 :1 across and 10 to 20 I long. Where close examination was possible, welded units exhibit weak ("0") to strong ("L" and "P") flow foliation. Resulting horizontal partinge were also observed in ej ecta blocks and in the core. Vertical joints and my of the foliation partinge are veneered with secondary deposits. Joint trends observed along the crater wall are in general agre-ent with surface mapped joints. Figure 41 presents major and minor joint trends for the "U" and "L" units observed on those crater wall surfaces not covered by fallback. Heasurenents were made fron the sane photo set used in napping the crater lip. Results are sona- what difficult to interpret because the wall is partially covered by fallback, there are numerous jagged reentrants, and local blast fracturing tends to obscure sons joint feces (particularly in the "U" unit) . In addition, orientation of joints vary with depth and 110 U UNIT (1. 8 - 8. 5m) Moior Trend W E Minor Trend S L UNIT (9. 8 - 29.9m) N Moior Trend W E Minor Trend Figure 41. Major and Minor Joint Trends for Welded Units in the Crater Wall u‘l .- 3 r‘{ I x 111 azimuth, similar to surface joints (Fig. 9). Allowing for these constraints, _the major joint trend for the "U" unit is north-south with a minor trend northwest-southeast. With joints in the "U" unit orientated along a rectangular grid, as observed in the "U" ejecta blocks, an east-west joint trend should have been observed. Unfortunately, the south wall is covered by fallback and the north wall is badly fractured. Major trends in the "L" unit are also north-south with minor trends northeast-southwest and northwest-southeast, as might be expected with the observed hexagonal jointing. c. Cratering Effects The dominant effect of cratering on the wall was to open up existing joint and foliation separations several centimeters. Blocks were fractured, primarily parallel to horizontal foliation planes and secondarily parallel to vertical joint planes. A new set of diagonal fractures was developed and locally blocks were broken and brecciated. The "L" unit was least fractured and relics of its original columnar structure are visible. Traces of major through-going vertical joints are drawn on the crater lip maps. Joint paths are offset slightly, probably due to differential uplift and relaxation. Joints are most prominent in the "I." unit with some extending as far as the "R" unit. Major fracture planes, with dips clustered about 51°, are also traced on the crater lip map. Fracture planes are distinguished from joint and foliation planes in that they are fresh, less regular in path, partially 3:31:00 nae: era-”fl". ”eolb‘ an ‘ , m) I "t. 1 112 discontinuous, and diagonally cut joint and foliation planes. Displacements along fracture planes do not exceed a meter. The higher concentration of open joints and fractures on the west wall versus the east wall may be related to the greater distance of the east wall from SGZ (148 vs 112 m). Areas of intense brecciation vary locally and do not appear to be related to crests or troughs. Major fracture planes, on the other hand, tend to be concentrated beneath troughs; e.g. T-7, 8, and 9. Figure 42 presents a trace map of the ejecta flap and crater wall beneath Trough 9 (L:31). Blocks 2/3 m and larger are traced and brecciated zones, slump zones, and mapping units are outlined. Plots of horizontal block lenth (1) versus vertical block thickness (t) are presented in Figures 43 and 44 with data summarized in Table 3. While the largest blocks in the wall are from the "L" unit, mean Z-D size (1 x t) increases only slightly from "R" (1.9 m2) to "U" (2.0 m2) to "L" (2.4 m2). Most of the blocks are rectangular with 1 > t. ‘Mean l/t ratios decrease from "R" (2.1) to "U" (1.5) to "L" (1.4). For a given unit the larger l/t ratios, ranging from 5 to 9, are associated with the larger blocks. Blocks in the ejecta flap are more equidimensional (llt'v 302 less) and smaller (1 x t!» 502 less) than blocks in the wall. 4. Ejecta Flap a. Stratigraphy All in situ mapping units down through "p" (77.1 m) are present as mappable units somewhere along the crater lip. These units are well .11 CRATER LIP STA. L31 ‘ s (D F ,‘d' [1. «3:0“=‘1'//%’/’4‘fi/////>' 31.5341" °=’.’-,?'x"ay.’/I"Aifl/Jt’ézz/fiiifi/miyfi/ZITML U U Mews/.6 mam/IAQr/‘mmmem; Inflow. V/f’vs-a///':°'°=°‘::‘.~=°:°=i=:‘.:=:=:r . .l’qgiggzgsgg.‘0,’.§:§EO.0.0.0.0.0.‘:.. :. ...§§§§§zfé’$§§$§°§f.' o g R 221?... ”i=2." (fly-“b9 " r ’F'O‘ gefifitkyfi, 7);-algae. u 'd ”v e e o . . . . .e.e.e.e.e.e.o. ... : . s ge'o'f e e A Q U Wlfififiaf/ [- / ‘ '51 @‘v‘f’é‘é‘ad-rrfldsu W M "mafigmmwsfl' ‘ f; 711‘)‘ ‘4' 4 " ska-40* ‘- A ' ’ F?! L ....a laser a ‘ a ‘ ..‘l‘ .s g,- nv-z£%‘%§ r V » e e e 3 0 0.0.3.. NOTE: Mapping Uni" covssso (TALUS) m I. R. U. M. L. a and a, Figure 42. Trace Map of Welded Blocks in the Ejecta Flap and Crater Wall Beneath Trough 9 THICKNESS -t (m) THICKNESS -t (m) THICKNESS —t (m) 114 3 x \I“ 2 I— 1 +- . mean m [R UNIT] . fl 0 l I l l I l l | o 1 2 3 4 s 6 7 a 3 s f ~° \ 2 v- . e m s _o' .s e .- , .. - ., . 5. 1 . [U UNIT] 1‘ - "I .7 a- ~25 - f 'a'. z;- . ' e f o l 1 1 J 1 l l I o 1 2 3 4 s a 7 a T Q V 4 L- . \_h 3 _ [L UNIT] I 1 I: ' 2- r - o a. ~10 -: J .- e I u .- I- a I so 0 ‘ t , z a - . . 1- '} v '5‘ " k ' ’ 3. f I 'l c 1 L l l l l l I o 1 2 3 4 s a 7 s LENGTH - l (m) Figure 43. Size and Shape Distributions of Welded Blocks in the Crater wall - Trough 9 THICKNESS -t (m) THICKNESS -t (m) THICKNESS ~t (m) 115 Figure 44. _1 L 4 5 _l 2 3 LENGTH - l (m) Size and Shape Distributions of Welded Blocks in the Ejecta Flap - Trough 9 F ,9 ‘9 \.\ “ [R UNIT] L- . meon V! L 1 A L 1 1 0 I 2 3 4 5 6 7 [U UNIT] 1 l 1 1 4 5 6 7 @UMfl 116 o.mnm.o 0.7.20 mo.~ o.~um.o c.mle.o mm.a fianfio no; m.~|~.o ownum _o\H_ sense mm.o «Aoo.Hv m~.N oH.H -.H Ho.e om.a am.e ea.~ ma.o me.o ow.o m~.m oa.o mo.m Ha.o «a.» ~o.~ ea.~ nH.H em.o Ne.e ao.o~ se.e ee.m ee.H mm.m~ oe.~ h~.e m~.H Cg INI .5 M afllv alv _o n ”a uou< _o_ unannouea a Hmmmu H4 m P > R,U > M > B,O > Y >>> c >> g,y,m,l > p > w". Where brecciation occurs, "P" blocks are typically smaller than "Y" blocks. There are local variations in fracturing; e.g. "L" blocks in T-6 areaone-half as large as those in T-7 and "L" blocks in C-9 are twice as large as those in C-8. However, there is little correlation of block 123 size with crests or troughs. 5. Soil Horizon The soil horizon thickens and thins about the crater reaching a maximum of 4 m on the east (L:14-17) and thinning to near zero on the west (L:31-38). Where the soil horizon is absent, location of preshot ground surface can be inferred by either the caliche coated "R" unit or by a narrow band of scattered vegetation, both of which are closely associated with the soil horizon elsewhere. The soil horizon consists of the in situ unit directly overlain by the overturned ejecta unit. Observation of plant roots in the one accessible soil outcrop area beneath T-2 (L:6) indicates that the thickness of the ejecta portion of the soil horizon varies from l/2 to 2/3 that of the in situ portion. This factor was used as a guide in drawing the hinge line about the crater. The soil horizon is not continuous about the crater; but «Slanted with most breaks aligned along the previously discussed din8011411 fracture planes in the wall. Vertical and horizontal dis- Plflceflents range up to a meter and soil horizon segments are tilted a f" degrees with respect to each other; e.g. L:7, 14, 20, 30, and 38. This tilting suggests differential movement during uplift, relaxation, or both. Since fracture planes extend up into the ejecta flap, these planes were active during the relaxation phase. Other structural features visible in the crater which may be rehted to differential upthrust/relaxation movement include: a Possible slump covered fault below Trough 4 (L:12-14) with a vertical 124 offset of 3 m and the displaced soil horizon segment beneath Trough lO (L:34-35) with a vertical displacement of 1.5 to 3 m. The sharp increase in thickness of the soil horizon beneath L:14-17 is probably the result of local in situ thickening since the underlying "R" unit remains nearly constant. B. Geology of the Trench 1. Physical Setting A 350 m trench was excavated along the length of Ray 1 from the crater rim to near the ray terminus, 500 m from SGZ. The trench intersects the crater to the west of C-1 and remains on the west side of the R-l axis until 340 m, where it crosses the axis and finally terminates 80 m to the east. Along this path the trench transects a number of key features of the Schooner ejecta blanket, exposing their structure and stratigraphy with depth. The outer half of the trench intersects the preshot ground surface while the inner half bottoms within the overturned "L" unit. The trench has an average width of 5 m. Its walls range up to 4 m, ‘with typically the lower 1/2 to l/3 covered by debris. The ejecta ‘portions of the trench walls are nearly vertical except for the first 30 m where slopes as low as 45° occur. The debris, from erosion of ejecta fines along the trench, (does not overly detract from the mapping since it is discontinuous and in.many places thin enough for ejecta units to show through. In .addition, mapping of the trench was supplemented by observations of on: u- 125 the trench floor and of material excavated from the trench (trench- ings). Figure 46 presents an enlarged photograph of a portion of the trench cutting through Crest 1. Selected photographs of other portions of the trench are presented in Figures 47 and 48. 2. Mapping Procedures The east wall exhibited the best exposures and was mapped in its entirety. Selected areas on the west wall were mapped for 3-D comparison. Stations T:-6 through T:112 were established at approximately 3 m intervals and surveyed to i 0.3 m horizontally and 3: 0.15 m vertically. Color photographs (35 mm slides) were taken perpendicular to the trench wall and centered on each station with a field-ofdview that included the station on either side. Projecting at a constant scale (1 cm.- O.35m) base maps containing major features ‘were prepared for each station; details were added in the field. Each mapping unit ("t" and "v" included with "g") and mix unit was outlined in its entirety. Individual blocks over 1/3 m.in largest dimension.were mapped 1:1. Smaller blocks were also mapped, but only on a representative basis. Fallout, covering the ejecta blanket up to 10 cm thick, was not mapped. .A composite map, using the center 1/3 of each base map, was constructed with the established survey control. ‘The resulting Geologic Map of the Trench is provided in the map pocket and a generalized version is presented in Figure 49. 3. Major Features Five ejecta units are defined: blocks (B), fines (F), slightly Inixed fines (An), moderately mixed fines (Ax), and well mixed fines vouuouvmu 315 means: new 28.3.3.0. 50:03. :33 H umono swsoufi. museum. 05 mo :eunwouoem .3 one»: acorn momma. .M 1.. v . 127 T=32 T:40 Figure 47. Selected Photographs of the Trench with Trench Stations Indicated (Clip Board is 35 cm Long) 128 1387 Figure 48. Selected Photographs of the Trench with Trench Stations Indicated (Clip Board is 35 cm Long) 129 museum. on» no as: sumoaoou non—Hansen .3 ensur— 25 N8 20mm mozgflmun 8. one a: 8.. 8.. or. one 8.. 2.. 8.. d d Ar: mZOEkBm mozm MA. «2 o: 3— no. no. no. 02 no no we «o co 3 3 no «m cm §§§\\\\\\§§\\\\\\\\\\\\\V\x\\\\\\\\\\\\.SSe\\\\\\\\\\\\\\\\\\\\\\\\\\\§.....\\\\\\\\\§.\\\.\.\§.\H\.\wemewmxl1aelem:a.......gfica......l..l._.....§..§“.. o ? ......... .....IIICQI 1211... _ Queen—am 151525 . am 3” am a n 52 e 32... I 135:! -2 35... mood :33 E .5 xi g «:2: E: New some mozfima can 8” 2n e8 8m 8n 8.” 8” 2n 8..” 2m 2m 2." on" $5 mzoueflwm mozmmm. SE eheafifiaeeezueoes833833....«43835 _ as: .. ...-3:233:22: a . an. . «f .1 ............ .d. ...... . I“ a“. . ._ 1 oomboosgpgageefaoefl ggfiazw‘eeuafiu} A... .prvu.:.cm..l....a.......w.11.ku . 9 u O .8. . . ..d . ...... ... ...... usual.“ .. JD... .8. \V\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\§§sV\§m....§\\\\\\\\\\\\\ew ,. ...“..-mhw 22.$5....”“seem“...sws........ .2... 2....»5. v.32? .....flusfze . T ........ . . . 2...-...... . 21:... .... ... BUY. 2:.Z::~:::m\. :22: thus-M”. ..... “...... . ... ...:.a.‘ vmvamxmsvvp.‘“v.e.w\.s.\.:.~.\..h... .....a...“ .. A , . . ..~.~.“.‘.h.uu.............m ........... 0 mm o . e ... « cm a O— AEV N Um 20mm m OZ m0 om 60'! _ o L g 1 J l l J l 1 o zoo too 600 son 1000 mo DISTANCE FROM SGZ (m) Figure 60. Frequency and Cumulative Frequency of Secondary Craters as a Function of Distance from SGZ 100 90 IO CUMULATIVE FREQUENCY (percent) 183 Azimuthal distribution of secondary craters about SGZ varies up to 1762 about a mean of 41.5 impacts per 10° sector (Fig. 61), but neither peaks nor lows appear to correlate with rays or valleys. The high concentration of secondary craters near 140° and 225° are aligned with the downhill and maximum ejecta directions, the latter probably associated with the previously discussed jet (Fig. 10). Reason for the large increase in 1.5 to 3 m craters on the west is ‘unknown, but may be due to the relative sparsity of vegetation in this area, resulting in improved viewing conditions. C. Detailed Distributions Along Ray 1 and Valley 11 Radials 1. Mapping Procedures Blocks (and secondary craters beyond 610 m) were counted in the field within 53 sampling areas distributed in a geometric pattern 'with respect to R-1 and V-ll radials (Fig. 57). All sampling areas *were 30.5 x 30.5 m except those along the 457 and 610 m circumferential lines which were reduced to 15.3 m on a side because of the high density of blocks. Stations along the 1021 m.line were adjoined; thus, a continuous count was obtained within the 30.5 m band from 1670 to 195°. Blocks were measured along their longest direction and in the two mutually perpendicular directions. Each block.was classified according to its napping unit ("R", "U", or "L") and as to whether it ‘was coated by fused glass. Blocks from the "BOY" units were also (observed and measured, but except within previously mapped areas (see Fig. 51) or in localized areas surrounding secondary craters most 186 e O r I 1'3“ 320 340 L‘l ufi“ <: m ”u- \+ 3'. _. x > u ‘ ‘ I J ..P" s ‘h 'x 2 t. “‘ \ '5‘ ‘7? ’.—>‘ '-, L...“ <3 O I ~h‘, \‘ N. ‘ ad" ‘ a. " ‘ <\ ( 3 .,;° _., ”"~ ...—II") ';9 a. " 1' I ‘:~~ ‘m~~ .1 ~‘~ ‘~—I- f ‘QL ~\ \\ D \\ a" d ’7 ) g r ,’ 3 1’ l.“ ’dP’ / .. ”,’ /T’J ' gin-J ,1 < _.'4 o ’ é .. <~ ‘ / ....". d \-~~‘ <\ ..1 ‘K \____- l I z a I 2 "' 5 E . Ix. (K § 2 5 \\ - . E '0 E fie»~ O M o 0 ‘~, n .3 V " A -'-----‘L--- I l L I L l j '3 8 3 8 9 9 3 8 ( '0“) LONEflbi-IHJ 360 280300 240 260 100 120 140 160 180 200 220 80 AZ IMUTH (degrees) Frequency of Secondary Craters as a Function of Azimuth Figure 61. 185 such blocks were less than 1/2 m and their total rarely comprised more than 1/22 by volume of the total block population at any sampling location. Interestingly, blocks from the "P" unit were particularly sparce and where observed almost always had brecciated upon impact with largest dimension rarely exceeding 1/6 m. Deposits from below the "Y" unit were not observed. Secondary craters were measured in three directions with respect to the original ground surface; the longest diameter, the diameter perpendicular to that direction, and the maximum depth. In addition, the mapping unit of the impacting block was recorded. Less than 22 of all secondary craters observed were formed by "B" or "0" blocks and none were formed by "Y" blocks. Therefore, only "R", "U", and "L" blocks and secondary craters are discussed further in this chapter. Due to rapid decrease in frequency and size of blocks with distance, minimum block size counted was varied from 1 1/2 m at the 152 m.stations to 2/3 m out to the 610 m stations, to 1/3 m beyond. ‘While such a scheme is a compromise and admittedly less than ideal for good statistical analysis, it is believed adequate to meet the stated objectives of obtaining relative comparisons along and between the sampling lines. 2. Blocks a. Fused-Glass Encased Blocks By volume, 71 of all blocks measured were encased to some degree in fused glass with the percentage increasing significantly with 186 distance. Along the R-l radial, the percentage of blocks with fused glass increases from 102 at 450 m to over 902 by 1400 m (Fig. 62). The distribution is not regular due to secondary cratering; e.g. a number of large impacts with fused glass occur at the 914 m station. The percentage of blocks with fused glass along the V-ll radial follows that of R-l reasonably well out to 900 m, beyond the trend for V-ll is confusing, but totals fall well below those along R-l. Percentage of "L" blocks with fused glass reaches a maximum of 74% ‘near 750 m along radial R-l in comparison to only 312 along V-ll, also at 750 m. Overall, percentage of "L" blocks containing fused glass is greater than for "R" and "U" blocks out to 1050 m and 750 m for R-1 and V-ll, respectively; beyond there is little overall difference. Along the 457 m circumferential stations, blocks containing fused glass are sparce, being found at 182° on Ray 1 (22) and at 1940 in Valley 11 (62). At both stations percentages of "L" blocks with fused glass approaches 152. At the 610 m stations, fused-glass covered blocks are concentrated (N202) to the counterclockwise side of Ray 1 with percentage of "L" blocks increasing to 502. There is another small concentration on the clockwise side of R-l. Along the 1021 m arc percent of fused-glass covered blocks averages 42% and ranges from 20 to 402 towards V—l and V-ll radials and up to 852 along the R91 radial (Fig. 63). R ELAT IVE VOLUME (percent) ‘m I I I l ‘ 90 .— R-I ..———- v.11 -—-- so 70 - E I ' - I I i 60 - | I) | ' d I I I so —- ' I I . d I I '- I I I I = - I I 30 - | I I ' ‘ I I I 20 - ' I I | d I IO - ‘1 I l . | l l ‘ I l l ‘.5 l | l l ‘5 l l Lo 0 s o DISTANCE FROM SGZ (km) —Glsss igut with Fused t by Volume of Blozkgut . F . 62. 3:33. as a Function o as: landV-il 188 neouuoum assassins—8 ~33. SS 2: 9.3. 52:2 so 832:5 o as swan-sou 330732:— 53 save: no 35.—”ob an unsung 93 oo— aooamog 535?. a: oo— oo— 08 4—dq_d_fi_~dq-HI—-d added...,._.a._ . .4. q.j.d..4a. l —.> mmx< >MJJ<> oz< ><¢ :.> I L ... *8 u «M \ e9 . am f 5 . ....< T 4 «no . ..m I -.....I a n sssssss a I T. I.L T I m l .....c .228 .855 Em .38 Illlls eIIIIIIlIIIIIIIIIIJ eIIlJ IIIII I _l ..a pp..—»-L_L.».rblp)LP).P.PPPr-th-L—Pp_._..L.—-pP-I—-P . nc 9.5%: 8— (Iuoaxod) summon ammvxaa 189 b. Stratigraphy Blocks without fused glass exhibit an inverted stratigraphic order on both R-1 and V-l radials where percentages of "L", "U", and "R" peak successively outward (Fig. 64). The radials differ in two respects; first, the inverted stratigraphic order continues farther out on.V-ll (1250 m.vs 850 m) and second, the greater frequency of secondary cratering on R-l results in a less ordered distribution of blocks. For blocks 3_1 m the inverted stratigraphic order is slightly better defined. For the fused-glass covered blocks, there is little inverted stratigraphic order with "L" blocks dominating out to near 950 m. Note that for both Rel and V-ll radials the inverted stratigraphic order deteriorates where fused-glass coated blocks approach 202 of the total block population. Figure 65 plots percent volumes of "R +‘U" blocks without fused glass for the circumferential stations. At 457 m percent "R'+ U" reflects the Ray—Valley structure increasing from 20 to 302 on R-l to near 100% between R-1 and V-ll (near the Rb of R91) and then decreasing rapidly as the isolated segment of R-ll is approached. At 610 m.percent "R'+ U", while never below 602, exhibits a high of 981 near the R91 radial and a low near the V-ll radial; elsewhere "R +‘U" percentages are mixed. By 1021 m neither rays nor valleys are reflected with percent "R'+ U" oscillating between 65 and 952; the exception is at 181° which contains only small "R.+ U" blocks and several large "L" blocks from secondary cratering. RELATIVE VOLUME (percent) RELATIVE VOLUME (percent) 100 IN DISTANCE FROM 562 (m) Percent Composition by Volume of Blocks as a Function of Distance from 862 along the R-1 and V-ll Radials with Skewed Re and Valley Area Indicated - 191 veusuwvau mend hoHHw> was had 105m Aug gown-sum none: anon one .93 .smc on» used—sawed no .8325.— e as once: :9: ... ..m: we 35.—"oar he sauna-ones". unease .no one»: Ammonwoce =e§§< on. 8. o: . 8— 2.. 8a dun-‘dddqdufiuW—qd-u—d-qdfiq.qJ—qddq—qqfiqqd-q-qdduu—d-dddu. ll IL . ... T- e \b ~ 1 \ a a \ v s x a . To ...—3. a, a. I .l a . arlld so; . . a a. I a I a a. .. L a \\f a \q/ l a j 1 \ A / GI \ . \ a . \ // fl Ill \ m a H \ Id .1 \ /l\ m / \ 1’ 1| \ m L . . <\ / x . I I r. . [m I .25 .228 35$ 2“. .38 I... 1IIII6 o. IIIIIIIIIIIIII I. all... IIIII «a ..> ..z __.> 2.x 3.? 54...; oz< >3. p.-.—».-.-.hs—-.PL-.p-P..-.—.-...P....—.-P-—..P._~.pP_-. oc— (Iuaozed) awn'IOA 192 c. Size Along the R-l radial mean volume of blocks without fused glass decreases rapidly (0.015 m3 per m) to 700 m, gradually (0.0002‘m3 per m) to 1200 m, and then remains relatively constant to the maximum ejecta range (Fig. 66). Mean block volumes for the V-ll radial are similar to R-l near their respective continuous block boundaries, but decrease more gradually with distance such that from 700 to 1050 m.mean block volumes on the V-ll radial range up to a factor of 2 to 5 larger. Beyond 1050 m mean block volumes are similar along both radials. Blocks from.the "L" unit tend to be larger than "R" or "U" blocks out to 600 m, beyond block sizes are similar. Glass-encased blocks are slightly larger on both radials. Individual block volumes along the circumferential stations are related to the Ray-Valley structure of the lip (Fig. 67). At 457 m, mean.block volume is largest near the continuous block boundary of R-l (less coverage by fines), decreases into V-ll, and then increases toward R-ll. Within R-l fines cover blocks and sizes are accordingly reduced. Mean block volume of individual units also vary with the Ray-Valley structure. Near the continuous block boundary of R91 "L" i 0.57 m3, "U" - 0.23 m3, and "R" . 0.08 m3; while within v-11 "u" - 0.28 m3, and "R" and "L" - 0.06 m3. At 610 m, mean block volume increases toward R-1 and R-Z radials and decreases toward V-ll. Overall, block volumes range downward from "R" to "U" to "L" with "R" and "U" blocks following the mean volume trend, and "L" blocks exhibiting little trend. At 1021 m, mean volume varies from 0.03 to MEAN VOLUME (m3) 193 T I 1 T r T I I 1 L, (SJ) (:1) _ R-I .- With Fused Gloss 0.--...0 1.0 Without Fused Gloss o————-o q «k v-” 4 0 9 \\ With Fused Gloss D'---C . ‘ Without Fused Gloss D——-D .- \\ r P ii \ l 1 , II \ i H " 0.7 \\ | ' ‘ _- | 1 I \ I I 1 I ' | "‘ 06 \ | l | ' | I I 7 LIP I I ‘ -‘ I 1 I 05 I ‘ — l‘ ' ' - . I‘ i 1‘ 0.4 " “ l, ‘ —I p I I I - I, I | 0.3 . ‘ I - 1 _ ' I I 9 a 1 1 - x I\ I ‘ . \ 0.2 I . I \l \ d l 1 I y \ 1 I II \ p I ’ I I ‘ .0-1 [A /,\‘ f I ‘ \\ .. . . I J '° 'V I ' \ ._ . _ \ o I I I L I ' ‘1‘ - ._ I 0.2 0 4 0 6 0.8 1.0 12 14 16 18 2.0 DISTANCE FROM SGZ (km) Figure 66. Mean Block Volume as a Function of Distance from SGZ along R-1 and V-ll Radials 196 358:5 .23 mod.» 3. 5“ 333m 5:. 2833»... nope: :3 3.-....3 .5 a. 5.53 no 8383 a 3 2.33 x82 8»: .8 8.53 A8283 mass—NI. on. 9: 2. 8. 2.. 8" d u a q q 4 _ u 1 I— d a d 4 — q d d — q d a d 4 — q q u u q q 4 q 4 dI 4 q 4 q _ q 1 q d A q a d u I— . a q d d u q I I I 4 T l I I I I x I DID ... .8. I I of IQ ... so L oll.o ... 5. I L I L I I I l I .2... .220. .355 S“. .38 I I I'll II. llllllllll I II III I. _I e: I. e ._ I a... ..> .... :.> 2... 3.2 5.3.; oz< >5. pF-p—pppb—pb.r—r.-.—--L----..—--nun-anpppbb-nkp—b- To «6 n6 (.0 ad 96 (maxed) awn'IOA mm 195 0.11 m3 in an irregular pattern without respect to the Ray-Valley structure. Unlike closer-in stations, there is little difference in mean block.volume between the various units. Glass-encased blocks follow a similar pattern, but tend to be 30% larger. d. Shape Three-dimensional block shapes were computed using Sneed and Folk's (1958) shape factor [up - (82/L1)1/3] where L! I, and S are the mutually perpendicular long, intermediate, and short diameters, respectively. Average block shape increases slowly, but steadily from 0.7 near 300 m to 0.8 near 1200 m with little difference observed between R-1 and V-ll radials. This 132 increase is probably more a reflection of block size than distance; i.e. shape increases slightly with decrease in size which decreases with distance. Near maximum ejecta range most blocks not broken on impact are equi- dtmensional, 1/3 to 2/3 m on a side and typically encased in fused glass. Along the circumferential stations at 610 and 1021 m shapes vary regularly;i§Z about their mean, but follow no particular pattern with respect to the Ray-Valley structure. Average shape factor is 101 higher at the 1021 m stations, again probably reflecting a decrease in size. Along the 457 m stations there is a trend to slightly higher shape factors along V-ll (less breakage?) compared to R-1 and R911. Fused-glass covered blocks tend to have slightly higher (&102) shape factors out to at least 900 m. 196 e. Volume Total block volume in each of the sampling areas along the R-1 and V-ll radials is presented in Figure 68. Areas over which blocks were counted have been normalized to the largest sampling area; but no factor has been applied to compensate for the changes in minimum block size counted nor for counting only on the surface of the continuous ejecta blanket. Therefore, inside the continuous ejecta boundary, plotted volumes are lower than actual volumes. While R-1 and V-ll radials contain similar total block volumes near their respective continuous block boundaries, beyond 700 m total block 'volume along V-ll radial becomes significantly higher. Total volume distributions of fused-glass covered blocks along R91 and V-ll radials are reasonably similar, particularly beyond the continuous ejecta boundary; but distinctly unlike the distributions of blocks without fused glass. Thus, whereas Ray 1 clearly contains the larger volume of blacks out to the continuous ejecta boundary, Valley 11 contains the larger volume of blocks beyond, by a factor of 2 to 8. This correlates with the larger number of impacts for valleys versus rays observed from event aerial photography (Fig. 15) and provides one line of support for extending the relationships observed between R-1 and Vell radials to the entire ejecta field. 3. Secondary Craters a. Frequency and Volume Frequency of secondary craters per sample area along the R91 radial decreases rapidly and regularly with distance (Fig. 69). The VOLUME (m3) 197 ‘03 I I I fl I T r I _I r l I I — -I - a I' -I R-I 2 With Fused Glass 9...... 10 r Without Fused Gloss o——o 1 E v -II I I. With Fused Gloss O----O _I ,. Without Fused Gloss O-—O ‘ I- .- 101 L" -I q -I E q —I '- .I P -I I- .. \\\ 10° .7’ \ . ‘21 - \ I b d I- [I .. " \ / \‘I _ - I \ - _ 2 r ‘ / \ / - I I / " I. If I "' -I 10 -2 4 I I I I I I J I l I j_ I 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 DISTANCE FROM SGZ (km) Figure 68. Block Volume as a Function of Distance from 862 along R-1 and V-ll Radials FREQUENCY (no. ) 20 r I t 1 I (j I T r I I T T I r I 18 I- .. I6 _ R 1 0-——-‘ d V- 11 e---~e " -I I4 '- -I b ‘ -I 12 '- .I 10 b . 8 I- I -I P -I 6 " -I ‘ '- a 2 " -I \ / o l I l L l I #4 J l l \k/l !) l 1 0 0.5 1.0 1.5 DISTANCE FROM SGZ (km) Figure 69. Frequency of Secondary Craters as a Function of Distance from 862 along R-1 and V-ll Radials with Skewed Ray and Valley Axes Indicated 199 R-l radial contains significantly more secondary craters than V-ll out to 850 m, beyond the distributions are similar. Total volume of secondary craters per sample area, which is proportional to the 3 per sampling volume of impacting blocks, reaches a high of 22 m area on R-l near the continuous ejecta boundary, but only 5 m3 on V-ll at 900 m. Along the 1021 m arc, secondary craters per sampling area average 5.7 and range from 1 to 11. There is a general decrease from east to west independent of the Ray-Valley structure of the lip (Fig. 70). Total volume of secondary craters follows the frequency distribution except that there are concentrations aligned with the east (10 m3) and west (9 m3) borders of Ray 1 compared to an average volume for all stations of only 2.4 m3 sampling area. b. Size Size of secondary craters along the R—1 and V-ll radials range from less than 0.03 m3 to a maximum of 9.6 In3 about a mean of 1.1 m3. While there is a general decrease with distance, secondary crater size is controlled to a large extent by local ground conditions with little difference between the two radials. Along the 1021 m arc, size of secondary craters averages 0.5 m3 and, similar to block size, exhibits no trend with respect to the Ray-Valley structure of the lip. There is also little difference in size between secondary craters formed by either the "R", "U", or "L" units. c. Shape Aspect ratios (Ra/Da) of secondary craters along both R-1 and and V-ll radials range from 1.5 to 6.5 about an average of 3. Shape, 200 33 «an» acne: .33 use moose 5353 no .8335 a so aueueuo hueosouem no muses—Venn .oh enough $8..on 5.225... cm— oo— a: 92 02 can lfiJ—fi.47—fidqq_qqn.—quu. q\/. dfidu.4dq.q—d o r . .\ ../..... N I — .- M. \c.‘ ..< 1 n T .\ ... x I ...\ ....- \\ 1 M ’u. (‘4... con \\ I . o . see so. I. V a m \a I \ \ x mm \ ... \ fl . . \ v ...u\ 1 fin " ...-(x o > \ fl ’ \ x ’ V I n .I \\ /P I\ r . N W b\ I WIK .(ILI .- 1 .s - N I o :l:I u a - - ,x c - - -\ i a s . ~ Q L h ......... D f s — u ’ ~ ¢ ~ F a ~ ‘ — .I a I m a u ’ — a s — ~ I III mi /- - Io s . I. . ~ I r .. I:- = I _ L_- r I «— 75¢ .330. Aeocomv Azu— :40- fillwlll YIIIIIIIIIIIIIIIIJ flIJ III!!! I, 2. :.> : .- mwx< >u.-.-<> oz< ><¢ pr.—_».b_»p.__»...rpb..—.ru__.___—.—-._...._...._.. ( '0“) KONHHDEIHJ 201 like size, appears to be related primarily to ground surface conditions; i.e. the deeper the soil the greater the depth and smaller the aspect ratio. Aspect ratios of secondary craters along the 1021 m are vary from 1 to 4 about an average of 3 and like size exhibit no trend relative to the Ray-Valley structure. d. Stratigraphy For all secondary craters measured, the relative percentages of the impacting blocks were: "L"(35%), "U"(442), and "R"(ZlZ). While both the "R" and "U" percentages are increased with respect to in situ, 3.5 and 1.7 respectively, there is only a slight indication of inverted stratigraphic order with distance. Along the V-ll radial, secondary craters formed by "R" blocks dominate between 700 and 900 m reaching 60% by number and 902 by volume of the total population. Along the R-l radial "R" unit secondary craters are concentrated between 700 and 850 m, but do not exceed 402 by number or 201 by volume of the total population. Beyond 900 m "R" secondary craters make up only a few percent of the population on the R-l radial while on the V-ll radial "R" secondary craters are present in near equal volumes to secondary craters from the "U" and "L" units. Along the 1021 m stations "R" and "U" secondary craters exhibit average volume increases over that in the core of 5.5 and 1.5, respectively, while "L" secondary craters are decreased by a factor of 3. CHAPTER VIII RELATIONSHIPS BETWEEN THE GEOLOGIC SETTING AND THE CRATER AND EJECTA FIELD The Schooner crater and ejecta field and the processes involved in their formation are the result of a set of complex interactions between parameters of the source and the geologic setting. A.major hypothesis of this study is that certain geologic parameters of the Schooner site played a dominant role in the formation of the crater and ejecta field. Although few of the processes or resultant effects could be observed in their entirety, many important portions were, and have been documented in the preceding chapters. This chapter first briefly compares Schooner to three other buried nuclear events and then assesses the effect of key geologic parameters on the observed crater and ejecta field. A. Schooner Compared The Schooner site was specially selected to combine strong and weak layering with a water table, a geological setting not previously tested. 1. Crater Shape The shape of Schooner's crater differs from other buried explosive craters in two important respects, its steep wall and its shallow flat floor. Figure 71 compares the average crater profile of Schooner with average profiles of Sedan, 104 KT in desert alluvium; Danny Boy, 0.42 KT in basalt; and Cabriolet 2.3 KT in 202 203 1R. __2'l! A ‘ ssz / O l .‘ y'.’ 0' j .l ' . .r’ . APPARENT ..w/ ' canes ,V// . / , / / / / ’ / I” / / R-3Pro‘ile ,/ / Average Profile ... fl / has. ....o" n 10? m f a/ ’ - '03. Vi / _— I I . I / l I I SCHOONER (ROCK/SOIL) seom (son) ..... TRUE r CRAT I ER DANNY sov (ROCK) ........... I]; CABRIOLET (ROCK)...— / I .0. / ",:w, Figure 71. Comparison of Apparent and True Crater Shapes from Buried Nuclear Detonations in Rock and Soil 204 rhyolite. Two additional Schooner profiles from Figure 29 are also plotted, the R-lO profile from the west or uphill side of the crater and the R-3 profile from the southeast or downhill side of the crater. Profiles were normalized by superimposing 862's and setting the apparent crater radii equal. As anticipated, the apparent crater profiles traversing the fallback portions of all the craters are similar with slopes typical of natural talus slopes. Also as expected, the upper portions of the true crater profiles for rock craters (Schooner and Danny Boy) are significantly steeper than the soil crater (Sedan). The major difference in profiles is that the true crater is exposed on over 752 of Schooner's surface while fallback covers the other true craters; i.e. relatively more of the material from Schooner was ejected. Figure 71 also indicates Schooner's floor is anomalously flat and that its average profile is shallow with respect to the other average profiles. Schooner's average aspect ratio (Ra/Ba) is 2.04 compared to values ranging from 1.55 to 1.89 for the other three craters. Applying the average aspect ratio from the other craters, Schooner's "corrected" apparent crater depth (Dg) would be 76 m or 202 larger than the present apparent crater depth. The volume of material between Da and D; is 1.91 x 104 m3 or 12 of the apparent crater volume. 205 2. Scaled Crater Dimensions Given the geologic setting and with proper stemming of the device, the yield (W) and the depth of burst (DOB) of the device determine the size of the crater and distribution of the ejecta field. Both were accurately measured (W 8 31 :14 RT and DOB - 108.2 m), while the vent history discussed in Chapter III demonstrates that the stemming was adequate. Figure 72 compares, on a scaled basis, Schooner's apparent crater radius and depth, to current prediction curves for buried nuclear events in dry hard rock (data base primarily basalt and rhyolite) and dry soil (data base primarily desert alluvium) (Fisher, 1968). As observed, Schooner's scaled radius is only slightly smaller than that of a soil crater. The present scaled depth is slightly smaller than a rock crater; but the corrected scaled depth (Dé) is very close to a soil crater. While there are no curves for layered media, Schooner would be expected to lie between the soil and rock curves and most probably closer to the rock curves. Thus, clearly the Schooner crater is significantly larger than one would predict using current empirical techniques. Code calculations by Terhune (in Lessler, 1968) based on first principles and using the measured properties of the site, like- wise predicted a significantly smaller crater: Ra - 20Z low, Da - 72 high, D; - 112 low, and Va . 40% low (where Va - FnRa2 Da and F - 0.46, an average shape factor for Schooner). m .2 "U {U m A V Q .... E-' M \ \E/ V) Z 9. CD E E Q ‘11. r-J < O 1: "3 ‘5. Q) Q tigure 7'2. 60 10 60 206 1 1 1 l 1 1 0 10 20 30 4o 50 50 70 l l I I I T Soil —--— Da' /” ~\\\ / \\ \ \\: 1 1 1 1 1 1 -60 SCALED DEPTH OF BURST (m/KT1/3°4) 70 Sealed Crater Dimensions for Buried Nuclear Detonations in Rock and Soil 207 3. Kass Balance For cratering events, the mass of material affected should be nearly conserved. Thus, analysis of mass partitioning using mass balance ratios provides a means of quantifying the cratering processes. Mass balance ratios, described and calculated in Appendix D, are presented in Table 4 and compared with similar ratios for Sedan. The apparent differences in cratering processes between Schooner and Sedan are significant in two respects. First, on Schooner ejection was a dominant process with over twice the relative material ejected as on Sedan. Second, net compaction on Schooner was a minor process being less than one-third as great as that of Sedan. 4. Distribution of Ejecta.Hass Figure 73 compares ejecta distributions in terms of incre- mental nass as a function of crater radii for Schooner, Sedan, and Danny Boy. Although over 802 of Schooner's ejecta mass is composed of welded tuff blocks it is distributed significantly farther out on a relative basis than the basalt blocks of Danny Boy. In fact, out to 3 Ba Schooner and Sedan ejecta distribution are nearly identical. Beyond 3 It the remaining 202 of Schooner's ejecta mass is distributed relatively closer to the crater than Sedan; but still extends over four times farther than Danny Boy. 3. Relationships There are a number of important relationships between the crater and ejecta field and the geologic setting. These range from 208 TABLE 4 MASS BALANCE RATIOS FOR SCHOONER AND SEDAN Ratio Schooner Sedan gem: 0.43 0.20 11f In: 0.47 0.43 111:/11c 0.01 0.01 MAIN: 0.09 0.36 mm, 0.53 0.57 tin/Ht 0. 11 0.05 Ham. 0. 80 0.36 "ems 0.88 0,42 Name 0.09 209 you w— »on mass: use .smcem .uusoosum new menu sassy-«n mo souuoosh e as suoenu we sowusawuuewayaeuseseuusu Q5 New 205 moz<$5 o— I. N— o— »Om >ZZ+160)] '- 1— I 4 he . r :.94 1 b d -20 1 1 L 4 1 1 L -1.5 -1.0 -.5 0 .5 1.0 1.5 2.0 2.5 217 nonetheless in the right direction. Possibly more important, the unequal cavity growth might be expected to produce an earlier and perhaps more sustained vent on the downhill side which could explain many of the above observations. The large radial vent is aligned and might be responsible for the gap in the crater rim, large slump failure, and shallow profile of the crater between 115° and 135°. A similar feature on the Sedan crater was associated with such an early vent (Strohm, et al.,l964). Continuing this argument, if the vent were large enough, it may have broken up and dispersed the mound section of Ray-3 resulting in poor ray development. This could account for the larger than usual amount of fine fallback and the more widely distributed block field. Vesic, et a1. (1967) also observed that while ejected material had approximately the same velocities, exit angles were steeper on the uphill side. This could explain the relatively fewer observed ejecta impacts on the uphill side since they would impact closer to the crater and thus be more easily and sooner obscured by the base surge and mound disassembly. Additional evidence supporting this is that 2 to 3 times as many secondary craters were observed on the uphill side than elsewhere in the continuous ejecta field. It seems plausible then that the above observations are related, in the main, to some preferential channeling of energy toward the downhill side of SGZ through a combination of processes involved in asymmetric cavity growth, mounding. and finally venting. Since, according to Sargent and Jenkins (1968) the present surface gradient 218 likely follows the original depositional surface, perhaps some buried structural element paralleling and related to the surface gradient is responsible. Such a feature might be a linear or planar set of open flow fractures such as suggested by the caliper and density logs of the four holes drilled in the cratered region (Fig. 8). Possibly such fractures might contain a higher degree of saturation. b. Local Topography The surface topography also affects the local distribution of ejecta. Two stream cuts, 400 m.to the east and southeast of SGZ, selectively concentrated blocks over fines and large blocks over small blocks, apparently due to preferential downward tumbling. Along the southeastern quadrant ejecta contours, including the Rb and Rab contours closely follow portions of the preshot topo- graphic contours (Figs. 24 and 81). Most significant, on the downhill side of the crater (southeast quadrant) the surface is strewn for over 200 m with ejecta blocks beyond the Rab that have obviously tumbled from uphill towards the crater. This is in contrast to the uphill side of the crater where few‘blocks tumbled much beyond the ab. c. Soil Cover The depth of soil varies widely about the crater from close to zero on the west and northwest to l to 2 I along the southwest and southeast quadrants. This lack of soil on the west and northwest may, in part, explain the sparsity of observed impacts from overhead. That is the less the soil depth the smaller the secondary crater and 219 thus the smaller the resultant ejecta cloud. 3. Lithologic Characteristics a. Bulk Properties In Chapter II the geologic column of Schooner was subdivided into four physical property units: upper densely welded tuff (0 to 38.7 m), weakly welded tuff (38.7 to 61.9 m), nonwelded tuff (61.9 to 103.3 m), and a lower densely welded tuff (103.3 to 148.1 m) (Fig. 6 and Table A2). Each of these units possesses a distinct set of properties which in bulk were very important in the formation of the crater and ejecta field. The densely welded tuffs are hard rocks; they are strong, dense, brittle, low in porosity and permeability, and contain little water. Thus they retain a well developed and relatively open joint system while being susceptible to blast- and impact-induced fractur- ing. In contrast the weakly welded and nonwelded tuffs range from soft rock to unconsolidated; they are weak, low in density, very porous, and permeable. They are thus compressible and susceptible to stretching, thinning, and flow. In addition several horizons contain significant amounts of water which further decreases their strength while decreasing their permanent compactability as well. The net effect of these bulk properties is displayed by the structure and morphology of the crater and ejecta field which reflects the cratering processes involved. ‘Within the crater the dominant feature is the upthrusted and blast-fractured true crater wall of welded tuff which, because of its 1 - , . . , . -, I . , _w , - . . .1 . . ‘ . 1- . - --. . .. _. -‘ v v . .e ,. 220 inherent strength, maintains a slope averaging 65° (Fig. 71). With the vertical joint planes of the in situ welded tuff units, the wall should be more nearly vertical as observed along the mesa cliffs that surround the Schooner site. The difference lies in the amount of net upthrust at the wall surface, with the steeper, uphill portions of the wall perhaps reflecting less net upthrusting; i.e. less initial upthrusting or more late-time relaxation. The weakly welded and nonwelded tuff deposits along the lower oneéhalf of the crater are primarily fallback (and probably some flowback). Overall, these deposits exhibit a definite bulging out- ward (toward the ZF axis) indicating movement during and/or immediately after emplacement, probably as a result of their initially high water content (deposits are now dry). This initial water content would also explain their present light cementation, which is sufficient to maintain locally vertical slopes. The crater floor was emplaced prior to first visual inspection, 5 hours after the detonation, and more likely within minutes after detonation; but after fallback was emplaced. Its near perfect flatness suggests that portions of one or more of the high water content horizons within the nonwelded tuff became liquified during release of cavity pressure and flowed into the bottom of the crater. note that the present floor is nearly at the preshot level of the top of the "w” unit and several meters below its expected upthrusted position. 221 It is suggested that at least the floor and perhaps portions of the nonwelded deposits were derived by such a flowback.mechanism. As an added conjecture the steeper wall on the west might reflect more flowback of material than on the east. The floor is shifted in that direction. An alternate, and perhaps preferred, explanation for most of the weakly welded and nonwelded deposits in the fallback (not including the floor) is that they resulted from collapse of portions of the cavity roof upon venting and that these masses fell/ slid down the crater cavity to their present observed positions. Supporting this contention is the observation that in general, weakly welded and nonwelded units are located in the crater beneath crests deficient in these units. The bulging outward of these deposits may still be due to some flowback "pressure" from beyond the crater cavity. The fallback also contains blocks and mixtures of blocks and fines derived in part from mound collapse, but primarily from late- time and post-crater failure along the crater rim (the overturned hinge). These deposits are typical of natural talus slopes. The overturned flap above the wall maintains a slope depending upon the properties of the ejecta units. The welded tuff units become increasingly dislocated and bulked (decrease in bulk density due to breakage and rearrangement) with distance above the upthrusted preshot ground surface. Correspondingly, their slopes become increasingly shallower with distance upwards. The fine deposits exhibit shallow slopes and are slowly eroding into the crater. 222 In the ejecta field the most obvious consequence of the bulk physical properties of the media is in the bimodal size distribution of the ejecta. The welded tuff units produced boulder-size blocks and the weakly welded and nonwelded tuff units produced sand-size tuff fragments. Block sizes, together with total volumes, are important in the size and structure of the flap segments and in their post-depositional‘movement. Weakly welded and nonwelded tuff blocks are not observed; but some small masses of one or more of these units are present on rays partially buried by the top mix unit. These masses apparently had sufficient strength due to their water content and/or shock compaction to maintain their integrity during ejection, transport, and impact. During mounding. units were obviously subjected to tensional stresses, with the welded tuff units separating along joint and foliation planes. Upon impact units were further bulked. Crest flap segments, observed in the trench and along the crater lip, appear to have been gently "set down" since they retain to a large degree their in situ structure with only a minimum of bulking. ‘With distance outward and upward distortion and bulking increases. Bulked flap segments of welded tuff form the major topographic relief of the ejecta blanket. Movement of these masses after impact consisted primarily of en masse, outward spreading which increased with distance from SGZ due to increasing impact velocity. Frictional forces between the ground surface and the flap segments retarded the _1_ ah I»... 1‘ 223 movement, as evidenced by the generally sharp drop off at the continuous block boundary, the deflated areas near ray termini, and the "stair-step" structures just behind leading edges of rays. Along segment boundaries individual blocks tumbled downhill. The weekly welded and nonwelded tuff units contained within the overturning flaps were stretched as evidenced by their thickened, thinned, and often interrupted exposures in vertical cuts along the crater lip and trench. Where present in a flap segment they are observed to locally fill in underlying topographic irregularities indicating some local movement. With distance outward nonwelded units exhibit increased movement after emplacement evidenced by increased mixing with distance. The mix unit overlying both welded and nonwelded deposits exhibits strong flow characteristics. Viewed from the surface this unit smoothed out all topographic irregularities within ray interiors by filling in lows and flowing around highs. In cross section this unit is observed to have eroded previous deposits picking up 1/3 m blocks and transporting them outward for up to 30 m. The special flowing capability of this mix unit may be due to movement on a trapped cushion of air similar to that proposed for some major land- slides (Shreve, 1968). More likely it is due to a combination of a strong horizontal velocity component from the strong gas acceleration and the fineness of the material involved, possibly further mixed with air. 224 b. Specific Properties Terhune and Stubbs (1970) list in order of importance water content, shear strength, porosity (compactability), and compressibil- ity as the key material properties in cratering. Compressibility and porosity are the dominant factors in determining peak pressures while shear stress and its duration primarily determine the shock or spell velocity. Water content is most important since it decreases porosity, compressibility, and shear strength of the media while its vaporization increases spall velocity by up to 102 and most significantly provides "fuel" for a stronger and longer lasting gas acceleration phase. The initial shock and more importantly.the rarefraction wave breaks up the.media; i.e. forms the true crater. Spalling and more importantly the gas acceleration ejects the material; i.e. forms the apparent crater and lip. The Schooner site was selected for its high water content in several horizons which, as observed in the event photographs (Fig. 10), produced a substantial gas acceleration phase. Comparison of‘mound rise data from a number of events indicates that without the large gas acceleration phase the Schooner crater would have been significantly smaller. Layering considerations, discussed in the next subsection, would tend to further reduce crater size. According to Terhune (1976) without this strong gas acceleration phase the Schooner crater would have been significantly smaller due to infill by ejecta.deposited proportionally closer towards SGZ. ’11 225 In the preshot code calculation of Schooner discussed above, water in the nonwelded horizons above the shot point was allowed to vaporize only within the zone of tuff vaporization (&8 m from the IF). This resulted in a calculated peak mound velocity 30% lower than measured and consequently the calculated crater was considerably smaller than the actual crater. Butkovich (1971) modified the model allowing free water to vaporize out to its own partial pressure limit (~25 m from the 2P) and demonstrated that such a model would predict a peak mound velocity within 52 of that measured. Presumably the apparent crater dimensions would also have been proportionately larger and closer to actual values, but that calculation was not carried out. The higher water content of Schooner and the resulting strong gas acceleration phase probably account for its significantly larger crater (Fig. 72) and ejecta mass (Table 4) than would be predicted considering the geologic setting without the saturated horizons. The much smaller net compaction at Schooner versus Sedan can be explained by the higher water content at Schooner, especially the concept of liquification of saturated fine units. The substantial difference in the stratigraphic section ejected at Schooner (77 m) vs Sedan (10 m) is further evidence of the effect of Schooner's high water content. Finally, the strong gas acceleration phase at Schooner probably accounts for the distribution of ejecta signif- icantly farther out from the crater relative to the dry rock crater Danny Boy (Fig. 73) and as mentioned above probably contributes to in 226 the mixing and movement of fines after initial emplacement. 4. Layering The effect of the strong-weak-strong layering sequence on the cratering processes and resultant crater and ej ecta field, other 1 than the lithologic properties, is complex. The layering sequence is expected to have modified the distribution of energy during the shock and spell phases resulting in the ejection of material relatively closer to the crater thus producing a smaller apparent crater. Whatever the actual effect, it was obviously overwhelmed by other geologic parameters, primarily the high water content previously discussed. Terhune (1976) , who calculated the Schooner event, noted that particle paths were nearly all vertical which he attributed to the layered geometry since these results were not observed in his previous calculations of the non-layered events , Sedan and Danny Boy. Terhune concludes that without the large gas acceleration phase of Schooner to turn these paths outward, the ej ecta would have been deposited significantly closer to the crater and the apparent crater would have consequently been significantly smaller. Observations of the event (Fig. 10) clearly indicate that during early times, material was ejected nearly vertical, but later a strong horizontal component developed. There is speculation that the two hard layers may have effectively squeezed the middle weak layer. Such a "tooth-paste- tube" effect might have pushed portions of the weak layer back into 227 the formation, some of which would then be available for flowhack into the crater region after venting and reduction of the cavity pressure. Both the outward bulged, fine outcrops in the crater and particularly the flat crater floor could be explained in part by such a flowback mechanism which conceivably would be enhanced by this "tooth-paste-tube" effect. Vesic, et al. (1972) have observed a similar effect in small laboratory explosive experiments. When a charge was detonated in a weak layer underlying a strong layer (roughly the configuration of Schooner) the cavity formed in the weak layer was larger than for either of the individual layers alone. They attributed this to the top layer reflecting energy back into the weaker layer. 5. Joint Trends 'Major joint trends in the upper densely welded tuff units had a dominant effect on the distribution of ejecta. The Ray-Valley structure of the apparent lip, the ejecta impacts observed from over- head event photography, and the distribution of welded ejecta blocks in the discontinuous ejecta field all correlate with the joint system at the Schooner site. a. Ray-Valleyvatructure of the Apparent Lip Sixty-four percent of the axes connecting SGZ with troughs (l, 3, 6, 6, 7, 9, and 11) are aligned with joint trends that exceed the average trend (Fig. 75). Trough axes 2 and 8 are aligned'with joint trends that while slightly less than the average are more prominent than neighboring trends. The two major rays (1 and 7), in 228 R-4 (1.50) (0.73) R-ll (0.77) . ,, \ (0.87) RAY I V 8 VV 1.82 O 0| i l me'e's 1 .1 5?0 elevation contents in it. Figure 75. Correlation between Joint Trends and the Ray-Valley Structure of the Continuous 81 sets Field 229 terms of total accumulated ejecta (Fig. 28), thickness of the inverted stratigraphic section (Figs. 37, 49, and 51), and linear alignment of flap segments (Fig. 36) are bound by the major north-south joint trends common to all upper densely welded tuff units. The interme- diate rays (4 and 9), judged in the same manner are bound by intermediate joint trends. Finally the minor rays, in terms of one or more of the above criteria, are aligned with minor joint trends. Previous experience has shown for buried events in unconsoli- dated soil that a number of poorly to moderately developed, but randomly orientated rays are typically formed. For example, the Sedan event produced 6 moderately developed and 2 poorly developed rays, none of which extended beyond 2.5 R3 and all were randomly orientated (Strohm, et al., 1964). In a series of high-explosive experiments in plays at varying depths-of-burst 4 to 10 well-developed rays were formed extending outward to between 3 and S Ra (Carlson and Jones, 1966). The best developed set occurred at a scaled depth-of-burst only slightly shallower than Schooner. There was no azimuthal consistency between events nor symmetry with respect to SGZ. Rays also have been observed from buried events in rock (Johnson, 1962) differing from events in soil in that often one or more of the better developed rays can usually be associated with joint ' trends. Where the joint system is not well developed rays are poorly developed and randomly orientated similar to the case of unconsoli- dated soils. For example, both Cabriolet (Fransden, 1970) and Danny Boy (Nugent and Banks, 1966) with poorly developed joint systems, 230 exhibit no rays. It is postulated for Schooner, that as the mound expanded and hoop stresses increased, the vertical joint planes served as planes of weakness along which the mound preferentially ruptured. These breaks were possibly in addition to the two early vents to the southwest and southeast which may have been due to other causes; i.e. a buried geologic structure paralleling the surface gradient. It is suggested that the joint system of Schooner was super- imposed on a random mound rupture pattern that would have occurred if the media were not jointed. Therefore, the mound would break up into a number of radially orientated sections (like opening petals on a flower) such that the first breaks would form the largest and best developed rays and the last breaks, the smallest and least developed rays. Thus, it seems reasonable that the major north-south joint trend cm to the "R”, "U", and "I." units would open first and provide the best developed rays (1 and 7) in terms of the previously mentioned criteria. Areas where no dominant joint trends existed would break up last and provide the least developed rays. Perhaps many of the observed variations in the crater and ejecta field, particularly the relative skewing of the various segments and units within segments, are reflections of slight differences in the joint system with depth. b. Bj ecta Impacts Maximum accumulations of ej ecta impacts are aligned with trough axes and minimum accumulations are aligned with crest axes. Figure 76 23]. as: £9.95. use ueouu one 3er euoe nu seesaw.— oowuodouuoo A8833 EDEN< .ch euomqh con own can can can can own can com on. 93 o3 on. 02 co co 9. cm 0 _ — q _ d 1 d A a _ A J a _ - q _ NU no 0U 20 :U ”U «U mu '0 «00 .50 P LJIITT. . . i . - it - . up a... o... 2 h 2» 2. up n... v... n... o... 1 mg E 5:05. oz... 6. 5.58 1 . r 7 7 > > > \ \ / x y < /\ .2. 1x1. < 4 f L r L _ nd ed ..— n.— n.— w.— n.— S.L DVCINI SALLV'IIINIID HALLV'I SH 232 quantifies the relationship between the Ray-Valley structure of the ejecta field (Fig. 24) and the ejecta impacts observed from overhead during the event (Fig. 15). Plotted is a count of residual impacts averaged over a constant 6° azimuthal band centered on each crest and trough axis. Residual values were obtained for each of the original 10° sectors of Figure 15 by dividing by the averaged count of the two neighboring 10° sectors. This in effect eliminates trends due to topography, early venting, etc. The mean number of impacts for all crest and trough axes (if) is drawn together with the i one standard deviations boundaries. As shown, 82! of the trough axes contain more impacts than the mean (i) and 362 contain more than 371-10. Also, 66: of the crest axes contain fewer impacts than the mean (if) and 33: contain fewer than i-1a. It is suggested that as the mound ruptured along joint trends, welded blocks were preferentially channeled through the openings. With a vent opening beginning at the top of the mound (as observed in Figs. 10 and 11) and propagating downward towards the ground surface, exit angles would initially have been high and subsequently decrease with time. Furthermore, early-time ej ecta would have exited at high velocities under high cavity pressures and rapid streaming of plasma through constricted vent openings. As cavity pressure rapidly decreased and vent openings opened exit velocities would decrease. Such processes would account for the time history of impacts observed (Fig. 18); i.e. steadily outward progression of impacts followed by 233 an oscillation of impacts. c. Blocks in the Discontinuous Ejecta Field Comparison of the distribution of blocks in the discontinuous ejecta field along Rel and V-ll radials indicates that beyond the Reb there are significantly more blocks (by volume) without fused glass along the valley radial (Fig. 68). Such a pattern also suggests that the vent openings provided effective channels through which individual blocks were preferentially ejected. The fact that these blocks retained their inverted stratigraphic order out to the ‘maximum ejecta range (Fig. 64) indicates that the processes involved 'were orderly. Why there are as many blocks‘with fused glass along the R91 radial as along the V-ll radial is not known. Perhaps blocks ‘with fused glass exited at early times from the top of the mound and thus were not controlled by vent openings, but rather randomly distributed. Their lack of an inverted stratigraphic order also suggests such a process. 6. Joint Spacing and Foliation Characteristics The final size and shape of discrete masses that make up the ejecta field is a function of their in situ characteristics modified by the cratering processes including shock, spell, mounding. ejection, deposition (impact), post-depositioned movement, and post-depositional impact. The in situ size and shape of welded blocks is primarily a function of unit thickness, the vertical joint spacing and orientation, and the development and intensity of flow foliation. Weakly welded and nonwelded blocks are not observed in the ejecta field. Blocks 234 from all of the upper densely welded tuff units are observed, each exhibiting their own set of characteristic sizes and shapes based on in situ sizes and shapes modified by their inherent strength, particularly susceptibility to brecciation upon impact. The "R” blocks are limited by unit thickness (1 to 2 m) which is controlled primarily by intensity of weathering. While weather- ing is gradational downward, there are local zones of weakness along horizontal foliation planes that result in horizontal separations. Host separations are not pronounced; but provide a preferential plane of weakness, particularly on impact. Some are opened sufficiently to have been thinly veneered with secondary deposits. The vertical joint pattern is rectangular (90°) with spacing typically 2 to 3 n. Thus, "R" blocks are rectangular, l to 2 m thick by l to 3 m long (lengths are parallel to the unit's upper surface). The upper surface is typically irregular and desert varnished; many vertical surfaces are slightly curved and heavily coated with caliche. Blocks from the "U" unit are similarly jointed, but are not thickness limited (the "U" unit is 8 m thick); thus, they tend to be larger and more nearly equidimensional (l to 3 m on a side) while still trending toward rectangular shapes. The long dimension is parallel to the unit's upper surface because of horizontal flow separations; vertical surfaces are predominantly joint planes veneered with secondary deposits. Blocks from the "H" unit, like the "R” unit, are thickness limited (2/3 to 1 1/3 m). The "H" unit is fine grained and 235 homogeneous without foliation planes. Contacts between "U" and "L" units are sharp; but due to its lower degree of welding, separations usually occur a few centimeters into the "M" unit. Jointing is rare and vertical block faces are smooth, but uneven. Thus, typical block shapes range from equidimensional to rectangular with long dimensions 1 to 3 1/2 m.and parallel to the unit's upper surface. The "L" unit exhibits a moderate to well-developed hexagonal structure with columns 3 to 10 m across and up to 20‘m in length. With its well foliated nature, the effective in situ block thickness is on the order of 2 to'3 m and blocks are thus rectangular in cross section and hexagonal to subhexagonal in plan view. Blocks from.the "P" unit are similar to "L" unit blocks except they are intensely foliated with incipient partinge spaced every few centimeters or less. In addition, "P" blocks are more brittle. Close to the crater they are only slightly smaller than "L" blocks; but with distance they become smaller than "T" blocks due to their high susceptibility to brecciation. Blocks from the "B" unit are subhexagonal, but lack the folia- tion of the ”L" and "P" units. They are thus rectangular to equi- dimensional with long dimensions typically perpendicular to the unit's upper surface. Sizes range from 1 to 2 2/3 m across and 1 1/2 to 3 m thick. Blocks from the "0" unit are similar to "8" blocks; they are thickness limited, 1 to 2‘m across to l to 1 1/2 m thick. Both "8" and "0" blocks are vitrophyres and quite brittle. "Y" blocks are thickness limited and, unlike the "B" and "0" blocks, 236 exhibit neither hexagonal jointing nor foliation planes. Blocks are almost always equidimensional, 1/3 to I‘m on a side. Upper and lower surfaces are typically flat; vertical surfaces are fresh and without secondary deposits. As observed in the ejecta field the large majority of welded blocks retain to a substantial degree their in situ characteristics. Apparently little breakage of welded tuff blocks occurred during the 'mounding or ejection.processes. Peak stresses during the shock phase are estimated to have been between 10 to lOO’HPa within the upper densely welded tuff unit, sufficiently low for stress release to have occurred along joint and foliation planes. During spell and mound growth, tensile stresses would result in blocks further spreading along joint and foliation planes. There was some breakage of blocks along the crater wall which tended to parallel existing vertical joint planes and horizontal foliation planes (Fig. 42). There was also some breakage along the 'hinge line of the overturned flap as observed on the talus slopes beneath. In the ejecta unit lying immediately above the in situ unit the lowermost portions are gently overturned and their in situ structure is essentially intact. ‘With distance upwards, breakage of blocks does not necessarily increase; but amount of displacement and dislocation of blocks (bulking) does. Thus, except for along the crater wall and in the hinge zone, breakage of welded blocks appears to be primarily the result of depositional processes. 1 237 Breakage of blocks in the ejecta field is observed in and surrounding secondary craters, in lenses within flap segments, and most significantly within the large rubble tracts comprising the termini of most rays. Flap segments are apparently emplaced at low velocities since all such deposits even terminal ones, contain large surrounding areas of unbroken blocks (Fig. 34). The conditions necessary to cause brecciation observed in the rubble zones, are not well known; but appear to be a function of impact mass, impact velocity, impacted surface, and ability of the impacting mass to withstand brecciation. That is, for a given impact surface the smaller the mass the larger the impact velocity required for brecciation. This would explain the observed increase in brecciation in flap segments with distance, while also explaining why individual blocks that fringe the flap segments are not brecciated. Thus, the observed retarcs (local mounds of broken and brecciated material) represent an impacting massdvelocity condition intermediate to secondary craters and small flap segments. CHAPTER IX TEHE HISTORY OF CRAIER AND EJECTA PROCESSES A. General Sequence Terhune and Stubbs (1970) identify four sequential phases involved in the formation of a crater from.a buried nuclear detonation. ghggk. Shock wave is generated by the deposition of energy into the ground and travels outward. §pgll. Shock wave reaches the ground surface, a rarefaction wave is reflected back towards the source region developing tensile stresses which separate material by spelling it upward to form a mound. Gas Acceleration. Pressures in the media above the cavity are relieved and mound expands upward at a faster rate, driven by gas generated from the earlier vaporized media surrounding the device. Ballistic Trajectory. Venting reduces cavity pressure, mound disassembles and ejected material begins free fall affected only by gravitational and frictional forces. This chapter provides a detailed sequential history of processes involved in the Schooner event based primarily on the data presented and relationships developed in the preceding text. While individual Be‘l‘flmces are in general order, there is considerable overlap. Where 1”sable, real times are provided. hphasis is placed on the 238 239 ejection, deposition, and movement of ejecta after deposition which essentially continues Terhune and Stubb's (1970) "ballistic trajectory" phase. Since obviously neither all nor generally even substantial portions of the various processes are observed in their entirety considerable reliance is placed on inferences drawn from the final observed dimensions, morphology, stratigraphy, and structure of the crater and ejecta field. B. Detailed Sequence 1. Mounding Phase (0 to 1.75 sec) The mounding phase essentially incorporates Terhune and Stubb's (1970) shock, spell, and gas acceleration phases. (a) Energy from the Schooner device, a 31 KT source equivalent to 1.3 x 1021 ergs, was deposited in the media surrounding the shot point within a few'microseconds. (b) A.very high pressure (100-200 GPa) shock wave was generated which propagated spherically outward at superseismic velocity. (c) Device and surrounding media were vaporized, forming a spherical cavity which according to formulas of Butkovich and Lewis (1973) had a radius of «98 m. (d) Velocity attenuated quickly to the wave speed of the media as peak pressures decreased outward due to geometric dispersion and to the work done on the material through which it passed. (e) Beyond the vaporized region, materials were successively melted, compressed, crushed, displaced, and finally plastically and then elastically deformed. 240 (f) Extent of each zone was dependent upon specific material properties. According to Butkovich (1971) water was partially vaporized out to 5 GPa (~25 m from the 2?). (g) Ground surface began to rise at 0.08 sec when the outward traveling compression wave intersected the surface (a free surface) generating a rarefaction or tensile wave which traveled back towards the cavity. Media above the cavity was spelled upward layer by layer with a velocity representative of the energy trapped. Cavity at this time was nearly spherical (it had not "felt" the returning tensile wave) with a calculated radius of 16 m (Terhune, in Lessler, 1968). Shear zones formed close to the final true crater boundary. (h) Cavity growth below the ZP was retarded, but not stopped by the returning rarefaction wave. According to Closmann's formula (1969) final radius for the lower hemisphere of the cavity reached 47‘m. (i) Hound grew'upward with spall velocity increasing to SO‘m/sec by 0.2 sec; velocity then remained relatively constant until 0.6 sec. (3) Mound growth was asymmetrical, elongated to the northeast- southwest and shortened to the southeast-northwest with maximum radius reaching twice the minimum radius. (k) Upper cavity continued to grow driven by the high pressures of the vaporized materials (primarily water). By 0.6 see the gas acceleration phase become dominant increasing the mound ‘velocity to 58 m/sec immediately prior to venting. 241 (1) Highest measured peak.vertical mound velocity, 24 m to the southwest of SGZ, was 65 m/sec or 122 higher than that above SGZ. (m) During mound growth, hoop stresses developed by the expanding mound failed material in tension with welded blocks continuing to separate along joint and foliation planes. (n) anwelded units continued to be stretched and thinned. (0) According to empirical formulas of Butkovich and Lewis (1973) peak stresses in the upper densely welded tuff units ranged from 10 to 100 MPa, low enough for joint and foliation planes to provide adequate stress release paths. The net result was little crushing of blocks except near the true crater boundary. There breakage was limited primarily to separations parallel to existing planes of weakness; i.e. joint and foliation planes.. (p) Due to the strongdweak-strong layered structure of the site, portions of the weak nonwelded tuff layer were "squeezed" between the upper and lower hard layers with some of the weak layer pushed back into the formation. (q) As the mound grew, large circumferential cracks formed in the soil overburden due to gravitational sliding. (r) Immediately prior to venting the upper densely welded tuff still retained its in situ section intact; but due to spelling and the geometrical expansion of the mound was separated into individual blocks bound by vertical joint planes and horizontal foliation planes. The weekly welded and nonwelded tuffs, on the other hand, were significantly thinned due to compaction and flow. ‘a. 242 (8) First venting occurred directly above SGZ at 1.75 sec ‘when the surface of the mound was 88 m high. 2. Ejection Phase (1.75 to ~71 sec) The ejection phase extended from first ejection of material to last impact of material. (a) First venting was followed at 1.88 sec by three new vent centers equally spaced along a southwest to west are approximately 60'm from SGZ. (b) First vent expanded parallel to the elongation of the mound (northeast-southwest) and by 2.0 sec had coalessed with the other three vent centers. (c) Plasma, consisting of gases and melted ruff, began stream- ing out mound vents with highest temperature measured at 2590°C. By 2.1 sec a broad triangular-shaped blanket of plasma covered the mound area. This blanket, centered some 60‘m to the southwest of SGZ, had its three vertices (lobes) directed to the southeast (135°), south- *west (225°), and north (355°). (d) Hot gases together with entrapped fines from mound disassembly were convected upward forming the cloud. (e) The plasma blanket continued expanding until 5.4 sec with the lobe on the southwest (225°) developing into a luminous jet approximately 60 m above the ground surface and extending horizontally out to 600 m.by 7.9 sec. Several other jets also formed, but none extended outward as far, nor persisted as long. 243 (f) Plasma blanket cooled rapidly, changing color from an original yellowdwhite to an orange-red by 5.4 sec and to a dark red by 8.5 sec. By this time the entire region had become obscured by debris from the disassembled mound which had reached a height of approximately 500 m. (g) Beginning shortly after first vent, radial cracks developed in the mound first along major joint trends, second along minor joint trends, and third in remaining areas without joint trends. Cracks propagated rapidly outward and downward from the top of the mound. One of the first cracks, perhaps due to a buried geologic structure, developed between 115° and 125° with a large and persistent plasma plume marking its location. (h) Eleven mound sections, formed by the radial cracks, separated as they continued to move upward and outward. Each remained hinged to the original upthrusted ground surface near the crater rim. (1) Beginning at 3 sec, several thousand luminous ejecta masses encased in molten glass (partially solidified plasma) and up to 3'm across exited the top center of the mound. Initial exit angles were near vertical. Boosted by plasma initially rushing through constricted vents, masses reached velocities between 300 and 400 m/sec. With.time, exit angles decreased to between 40° and 60° commensurate with downward development of the radial cracks. Exit ‘velocities decreased rapidly to between 60 and 130 m/sec with subsequent drop of cavity pressure. 244 (j) Beginning at 5 sec compressed and perhaps partially saturated nonwelded tuff masses exited the mound in ballistic trajectories leaving contrails of fines marking their trajectories. (k) With venting of high pressure gases upthrusting ceased and relaxation of the ground surface and cavity walls began. Non- *welded units originally compressed and stretched along the cavity ‘wall began to slump back into the cavity while similar units on the underside of the mound shell, not carried with the mound sections, fell down the cavity walls. (1) Portions of the nonwelded units, originally "squeezed" between the two hard layers and forced back into the formation, liquified upon release of cavity pressure and began to flow into the cavity causing further relaxation of the upthrusted ground surface. (m) Mound sections (flaps) continued to overturn and stretch outward causing each to break up into several segments including a "hinged" or crest segment, a terminal segment, and one or more intermediate segments. (n) The "elbow" of the hinge segment failed in shear and began to fall/slide into the crater cavity. ' (o) Flap segments followed general ballistic trajectories. welded units continued to separate and nonwelded units continued to stretch and in some cases became discontinuous. Degree of dispersion between and within segments increased with time and distance. (p) During the overturning, stretching, and breakup of flaps, discrete masses of ejecta were separated to form a dispersed fringe 245 zone surrounding the flap segments. Masses within this fringe zone followed ballistic trajectories of the flap segments from which they ‘were derived. (q) Throughout their trajectory flap segments retained stratigraphic order and individual units retained their integrity *with little or no mixing between units. With overturning the stratigraphic order was inverted. (r) During transit, ejecta masses were affected by drag with smaller masses (less than 1/3 m) preferentially winnowed out with distance such that very few reached 1200 m. 3. Deposition Phase (4 to ~81 sec) The deposition phase began with first impact of ejecta and terminated with last movement of ejecta on the ground. (a) Flap segments were emplaced in an orderly manner and in an ordered sequence beginning with the crest segments (4 to 6 sec) and progressing outward to the terminal segments (8 to 12 sec). Movement of ejecta continued for at least 10 sec after initial emplacement. (b) With the inverted stratigraphic order of the flap segments, welded tuff units impacted first and with their large volume, further enhanced by bulking, produced the major topographic relief of the continuous ejecta field. (c) Weakly welded and nonwelded tuff units were deposited with and on top of the welded units, filling in and smoothing out local surface irregularities. Except near the crater rim, where volumes 246 *were relatively large, these units did little to modify the basic topographic expressions of the welded units. (d) Emplacement of flap segments became increasingly disruptive with distance outward, corresponding primarily to increased velocity of impact and thus post-emplacement movement, but also due to increasing in-flight dispersion between units. (e) Crest segments were gently folded over and little disrupted with the now underlying welded block units retaining most of their in situ features. At the base of the crest segment, blocks ‘were little broken and retained their jointed structure. With distance upward this structure became increasingly disrupted. In terminal flap segments, no in situ structures were preserved. (f) Brecciation of blocks within flap segments increased with distance as impact velocity increased. The processes of brecciation were orderly with little mixing between units indicating that segments were emplaced en masse at which time brecciation occurred. (g) Movement of, and within, flap segments after emplacement increased with distance due primarily to increased impact velocity together with increased separation of flap segments ineflight. Movement was an orderly process with little disturbance of the inverted stratigraphic order. (h) For crest segments, movement was confined to minor outward sliding or "squishing" en masse and to individual blocks tumbling downhill. 247 (1) Movement of terminal segments after emplacement consisted of a general outward spreading of ejecta leaving a slightly depressed region, followed by a bunching up of ejecta in a "stair-step" struc- ture at the ray termini. Along leading ray edges small lobate masses of ejecta moved outward. Similar lobes were formed along lateral edges, but skewed radially outward from SGZ. Individual blocks from the fringe zones surrounding terminal segments, for the most part 'unhroken on impact, tumbled farther outward. (j) Movement of intermediate segments after emplacement was intermediate to crest and terminal segments. (k) Movement of weakly welded and nonwelded tuff units within flap segments also increased outward grading first into slightly ‘mixed and farther out moderately mixed units. (1) Following the emplacement of flap segments a well mixed fine unit was formed from the weakly welded and nonwelded units. Concentrated within rays, this unit covered all previous ejecta deposits, reaching maximum thickness near ray centers. This unit flowed outward, perhaps with the aid of entrapped air, sufficiently to smooth out most topographic irregularities. Portions of this unit flowed through topographic breaks in the underlying welded units "drowning" portions of several valleys. Little of this mix unit flowed across ray perimeters. (m) Individual weakly welded and nonwelded masses (streamers) ‘were deposited along rays from 8 to 15 sec. Impacts occurred after ‘the segments were deposited, but during the formation of the mix 248 unit. During this same time period small masses of these units were deposited along the crater rim. (n) Individual ejecta blocks, which exited preferentially through the mound vents, impacted regularly outward in a moving curtain traveling at an average ground speed of 55 m/sec until 25 sec. Impacts were concentrated out from valleys with up to 302 of these blocks encased in fused glass. After 25 sec, impacts oscillated back and forth partially filling in the intervening areas. ‘Most impacts created a secondary crater, secondary ejecta field, and cloud. There were, however, a number of l to 2 m conspicuous blocks impacted out to 1200 m which exhibit no secondary craters. Maximum distance of a recorded impact was 2134 m at 34 sec and last recorded impact was at 71 sec and 1067 m. (o) Emplacement of flap segments generated a base surge that expanded outward at an average ground speed of 20 m/sec. Outward movement continued to 1370 m by 71 sec. Vertical stabilization occurred at approximately 4 minutes after which the remaining mass was pushed downwind (northeast) at 1 to 5 m/sec. (p) Cloud development began after first vent and continued until vertical stabilization at approximately 4 min. Cloud then traveled with the wind to the east-northeast at 12 to 18 m/sec. Fall- out from the base surge and cloud, within the boundaries of the ejecta field, effectively ceased by 12 min. CHAPTER X SUMMARY, CONCLUSIONS, AND APPLICATIONS The study of Schooner provides for the first time detailed considerations on the dimensional, morphological, stratigraphical, and structural aspects of a relatively large explosively-produced crater and ejecta field. Relationships between the observed features and key parameters of the geologic setting are derived and then used to infer crater and ejecta processes. Two major conclusions emerge: (l) the Schooner crater and ejecta field were produced by a set of orderly processes (as detailed in Chapter IX) and (2) these processes were strongly affected by the geologic setting (as detailed in Chapter VIII). The application of these results to cratering is twofold. First, as an analog to aid in the interpretation of existing craters through direct comparison of similar features. Second, as a basis from which to hypothesize crater and ejecta processes for other geologic and source conditions. In any application of Schooner, appropriate care must be exercised because Schooner is one event with a singular set of source and site parameters. A. Orderly Processes Processes involved in the formation of the Schooner crater and ejecta field are believed to have been orderly because nearly all observed features of the crater and ejecta field are logically 249 H 250 superpositioned and stratigraphically ordered to the finest detail. The few unordered features can be explained by movement of ejecta after initial emplacement or by postshot slumping and erosion. ‘Where direct observations were possible, mounding. early ejection of 'material, and impacting of individual ejecta.masses proceeded in an orderly manner. The detonation of the Schooner device produced an apparent crater with a radius of 130 m, a depth of 63 m, and a volume of 1.7 x 106 mp. Over 902 of the ejecta was distributed continuously to an average of 510 m. Maximum ejecta range was at least 2150 m. Ejecta sizes are strongly bimodal with boulder-size blocks from the 'welded tuff units and sand-size fines from the weakly welded and nonwelded tuff units. The dominant feature of the continuous ejecta field is the Bay-Valley structure beginning with 11 crests (topographic highs) and intervening troughs (topographic lows) spaced unevenly around the crater rim. Some crests and most troughs form sets which are aligned through surface ground zero (SGZ). With upthrust nearly constant around the crater perimeter, differences between crest and trough heights are a direct function of the volume of ejecta contained. Crests and troughs continue outward as rays (concentrations of ejecta) and valleys (little to no ejecta), respectively. The distributional pattern of rays is similar to spokes radiating from a.wheel hub (the crater). The components of the Rey-Valley structure; i.e. crests, troughs, rays, and valleys are closely and logically related 251 dimensionally, morphologically, stratigraphically, and structurally. The continuous ejecta field is in near perfect inverted stratigraphic order. Overall, it can be viewed as an upside-down layer cake. In detail, the layering follows the Ray-Valley structure such that in traversing outward, either radially, or perpendicularly, to a ray axis, higher and higher in situ units are encountered. In greater detail, the truncated layers are discontinuous, with each ray consisting of several segments of a mound section arranged sequentially outward in a slightly skewed pattern. Ray segments moved along the ground surface to varying degrees after initial emplacement resulting in morphological and structural, but few stratigraphical, modifications. Distortion and dispersion of segments prior to deposition, brecciation and dislocation during deposition, and movement on the ground after deposition increased with distance outward. Thus, segments spread out and coalesce with distance, producing a general broadening and diverging of rays. Even so, stratigraphic units comprising segments retain their identity with only minor mixing even within the most distant segments. Segments are in turn overlain by a continuous layer of mixed ejecta fines which exhibits strong flow characteristics. This mix unit smoothed out topographic irregularities by filling in lows and encircling highs. It also eroded portions of the underlying ejecta deposits, transport- ing them outward for up to 30 m. The major portion of the discontinuous ejecta field is also related to the Ray-valley structure; but with distance, ejecta . e «4 ,. . .. a . . I r . a; i . t: a. Is a a C . r I 4. ;. IIE »~.‘—. 252 ‘becomes aligned with troughs rather than rays. Inverted stratigraphic order is preserved to maximum ejecta ranges, but becomes increasingly difficult to trace beyond the continuous ejecta boundary. This is ‘because there are two populations of blocks comprising the discontin- uous ejecta field. Approximately 72 of all blocks are encased in fused glass and were not deposited in an inverted stratigraphic order. The majority of blocks are not encased in fused glass and ‘were deposited in an inverted stratigraphic order. The ratio of fused- to nonfused-glass-covered blocks increases from less than 32 at the continuous ejecta boundary to nearly 1001 at maximum ejecta range. It is concluded that the crater and ejecta field were formed by the orderly break up of the mound into 11 major triangularly-shaped sections’which were ejected, overturned, and deposited en masse. The fact that rays and their component segments are ordered to the finest detail indicates that processes involved in their formation were likewise ordered. During breakup of the mound blocks of ejecta were preferentially ejected through mound vents (between mound sections) and followed ballistic trajectories to impact. The fact that the majority of the discontinuous ejecta field exhibits an inverted stratigraphic order indicates that the responsible processes were also ordered. B. Important Geologic Parameters Features of the crater and ejecta field can be related to one or more parameters of the geologic setting. Water content was clearly the most important controlling geologic parameter. The high water . . 253 content of some horizons within the weakly welded and nonwelded tuff units provided "fuel" for the strong gas acceleration phase. This was primarily responsible for the significantly larger crater and the more widely dispersed ejecta field than had been predicted, consider- ing the geologic setting without water. The large gas acceleration boost probably also contributed to movement of ejecta along the ground and the resulting formation of the mix unit overlying the stratified ejecta deposits. The high water content of one or more nonwelded units above the present crater floor was probably responsible for the late-stage formation of the flat crater floor. Finally, the large quantity of fused glass produced by Schooner was probably due to the ‘high water content. Overall strength of the various units was responsible for the strong bimodal size distribution of ejecta. Ejecta sizes together with unit volumes played a major role in the distribution and movement of ejecta after initial emplacement and the resultant structure and morphology of the crater and ejecta field. Major joint trends were important in controlling the formation and orientation of the Ray-Valley structure of the ejecta field by causing the mound to break preferentially along major joint trends producing the dominant rays. The more dominant the joint trend the more dominant the ray. As the mound disassembled, ejecta blocks were channeled preferentially through vent openings between mound sections. Joint spacing and foliation characteristics controlled the sizes and shapes of the ejected welded tuff blocks. The high degree 254 of jointing and foliation in the welded units apparently provided sufficient stress release paths, resulting in little breakage of blocks during early stages of cratering. Large volume breakage of blocks on impact was localized within flap segments. Therefore, sizes and shapes of ejecta blocks reflect to a high degree in situ conditions. The surface gradient of 1.50 across SGZ, while seemingly insignificant, correlates with a number of crater and ejecta features; e.g. mounding and venting patterns, crater shape, and ejecta impact patterns, such that cause and effect relationships appear probable. Either the gradient was directly responsible, or indirectly responsible due to some buried structural feature reflecting the present surface; e.g. a set of flow or fracture planes. C. Applications The observations and analysis of the Schooner crater and ejecta field are potentially useful in generalizing to other explosive events within constraints imposed by Schooner's source and site characteristics. As an analog, the observed features of Schooner can be compared to similar features of other events to aid in the interpretation of geologic settings and crater and ejecta processes. In this sense surface morphology and geologic charac- teristics of the ejecta field are indicators of the subsurface stratigraphy and structure. In addition, the now well established details of the Schooner crater and ejecta field provide a basis for 255 the design of mapping, sampling, geophysical studies, etc., for other craters and ejecta fields. Schooner also can be used as a basis from ‘which to generalize to other cratering situations; i.e. variations in the geologic setting, yield, depth of burst, mode of energy release, (chemical, nuclear, or impacting meteorite), and planetary parameters (gravity and atmospheric pressure). In support of the above, the Schooner crater and ejecta field provides a ready means for testing hypotheses and for searching out and examining in greater detail features observed on, or hypothesized for, other events. Thus the importance of Schooner lies not only in its immediate application, but in its future use as an interactive analog. In the application of Schooner's results to other cratering events care must be exercised because Schooner is one event with a singular set of source and site parameters. 0n Schooner, there is ample evidence that the effect of the various geologic parameters on crater and ejecta processes were superimposed. For certain conditions, one parameter may even completely negate the effects of another; e.g. on Schooner the high water content probably negated effects from the strong over weak layered geometry. In general, where first order features of the crater and ejecta field of another event compare favorably to Schooner, then at least some of the higher order features, studied in detail on Schooner, are to be expected. Major differences between events should then be primarily a consequence of differences in the geologic 256 settings. Differences between source and planetary parameters are also important, but probably to a lesser degree. Overall, as an event's source and site parameters increasingly diverge from those of Schooner's, then increasingly greater care must be applied to extra polation. Within these guidelines it is safe to expect reasonably direct application of Schooner results to other buried explosive events and to the large class of bowl-shaped meteorite craters. The latter, ‘which includes Meteor Crater, Arizona, range up to 10 km in diameter on the Earth and possibly as large as 20 km on the Moon. General application of Schooner to cratering is discussed below. Neither specific events nor specific geologic settings are included, since the range of possibilities is great and the necessary details are either hypothetical, insufficiently defined, or simply not available. Nor is any attempt made to include effects due to source or planetary parameters since these have been considered by others. Specifically, Nerdyke (1961) has discussed explosive source parameters, Chabai (1965) has assessed gravity parameters, and Oberbeck (1971) has contrasted impact and explosion sources. Investigation of the Schooner event has demonstrated that the best approach in examining a cratering event and interpreting the processes involved in its formation is to begin at the crater edge and work outward. Since cratering processes and resultant features are ordered, observed stratigraphic and structural features at the 257 crater edge provide the key to what lies outward. .Along the crater ‘edge the most complete and undistorted inverted stratigraphic sections of ejecta are preserved. Beyond the crest, good strati- graphic sections can be obtained at topographic highs (flap segments), 'particularly along the dominant rays. While inverted stratigraphic order is to be expected in the discontinuous ejecta field, sampling can.lead to erroneous results without careful attention to the 4continuous ejecta field, particularly where there is no well defined ‘Ray-Valley structure. Since nearly all ejecta is distributed radially outward from the crater in a symmetrical and orderly manner, departures from such symmetry and order indicate either nonsymmetrical cratering processes or more likely discontinuities in the geologic setting. Regular departures from crater circularity may be due to regional surface gradients as small as l l/2°. Local and abrupt departures from circularity are more likely caused by local venting or postshot slumping, both probably related to geologic factors. Whatever the cause, the ejecta distribution radially outward should be accordingly perturbed. Departures from cross sectional symmetry of the crater are due to either excavation or fallback. Both of which are primarily geology dependent and should be traceable in either the ejecta field or the fallback. It appears that in general, explosively produced events are capable of generating radial concentrations of ejecta (rays) although other geologic factors (small gas acceleration phase due to 258 low’water content, certain layering sequences such as a thick soil layer over rock, etc.) may inhibit their development or conceal their presence. Thus, the presence or absence of rays is neither necessary nor sufficient to indicate the presence or absence of joint trends. However, dominant joint trends are indicated where dominant rays exist (in terms of size, volume, linearity, etc.) and particularly where ray sets are symmetric through SGZ. On Schooner, primarily as a consequence of the water saturated layers, the Ray~Valley structure is particularly well developed, extending continuously out to an average of 510 m (3.9 Ra) and discontinuously out to the maximum.ejecta range of 2150 m (16.5 Ra)° In addition, large blocks 1/3 to 1 m3 in volume were ejected to ‘maximum ejecta ranges. Thus on events where such features extend to similarly scaled ranges and with due consideration for gravity, the presence of water saturated layers in the geologic setting should be considered. Ejecta block sizes and shapes are a good reflection of in situ conditions for well-jointed sites. Where a lack of joint- faced blocks prevail in the ejecta field, excluding obvious brecciated zones, it can be reasonably concluded that in situ joint- ing is lacking. As in situ jointing and foliation decrease, then percent breakage should increase and block sizes and shapes should tend to reflect rock strength more than in situ structure. Aside from secondary craters, block breakage is concentrated within flap segments. Thus, the best place to observe blocks for interpretation of in situ structural characteristics is away from 259 flap segments; i.e. near and beyond the continuous ejecta boundary or along the crater wall or lip. Alternatively, the best place to observe blocks for interpretation of in situ strength characteristics is within flap segments. Since blocks can only become smaller during cratering, observed block sizes in the ejecta field represent minimum in situ sizes. Ejecta fines, on the other hand, can aggregate due to shock compression, presence of moisture, or cohesive constituents. Upon impact these aggregates are partially or totally destroyed, but in the process create secondary craters. Thus, ejecta fines are representative of the clast fraction of the in situ media, while aggregates (and the secondary craters they formed) can be useful in inferring physical properties of the media. A strong bimodal (or trimodal) ejecta size distribution, especially one symmetrical about SGZ, is indicative of a layered geologic setting. Where a strong over weak layered condition exists (as in Schooner) an inverted stratigraphic order is probable. As the thickness of the weak layer increases at the expense of the strong layer the block distribution will become increasingly covered by fines. A.Ray~Valley structure, if formed at all, may be concealed and its inverted stratigraphic order destroyed. For the reverse of Schooner; i.e. a weak over strong layered setting, the inverted stratigraphic order would tend to be destroyed 'with distance due to relatively higher air drag on the fines. Even dominant joint trends existing in the underlying strong layer may not ,.-.r A I fl ‘1. '\ .v'. , ... ‘ .. . . V I _ . 260 lead to preferred venting in the overlying soft layer. Or, if a ray ‘pattern is developed it may be skewed with respect to any ray pattern developed within the overlying weak layer. Obviously there should be little drowning of blocks by fines. Interpretation of event processes based solely on photo- {geologic mapping, particularly when the geologic setting is unknown, Inust be approached cautiously since similar surface features can be formed in different ways. Schooner has demonstrated that ejecta can move significantly after initial emplacement. Where deposited as large masses (flap segments), ejecta spreads out en masse. Individual 'blocks tumble and fines flow under dry (possibly enhanced with entrapped gases) and presumably, wet conditions. Where unconsolidated or weakly cemented layers underlie rock layers the fines generated ‘will be deposited last and their movement can cover and smooth out an otherwise blocky ejecta surface. Thus, smooth or level surfaces and surfaces exhibiting "flow-like" features can be the result of fine, as well as the more typically considered volcanic, flows. Schooner has also demonstrated that smooth features within the crater, particularly level surfaces, can result from the liquifi- cation and flow of fines from saturated zones. Thus, craters that do not contain a flat or level floor may not have contained a saturated zone of unconsolidated material above the present crater floor. If such a layer did exist, it may have been of insufficient ‘volume to produce a level surface. In this case partial filling of 'the floor or flow structures along the crater sides may be expected. 261 For Schooner little secondary cratering of the ground surface occurred during emplacement of the continuous ejecta blanket; i.e. beneath flap segments. While there was extensive secondary cratering of the ground surface during deposition of the discontinuous field, the volume of material affected was relatively minor. Finally, two miscellaneous observations. First, care must be exercised in using secondary crater sizes and shapes to interpret terminal parameters (size, mass, velocity, angle, etc.) of the impacting mass because ground conditions (soil/rock, soil depth, etc.) are usually the controlling factor in these characteristics. Second, in the interpretation of cratering events, it should be remembered that coverage and/or partial camouflage of the ejecta field, particularly within the continuous blanket, by base surge and cloud deposits can, until eroded, significantly alter the surface morphology. APPENDIX A APPENDIX A STRATIGRAPHIC AND PHYSICAL PROPERTY DATA FOR THE SCHOONER SITE Table A1 presents field descriptions of the 28 mapping units listed in Figure 6 and used in the geologic mapping of the crater end ej ecta field. Descriptions are based on megascopic examination of the UZOu-Z continuous core followed by correlation with ejecta deposits. Lawrence Livermore Laboratory measured physical properties of the Schooner media using both in situ and laboratory techniques. Results of their downhole seismic survey for the Ue20u-3 are presented in Figure Al. Their three-layer fit matches the superimposed physical property units of Figure 6 except for the velocity break at 42.7 m, which as shown by the dashed line can also be interpreted at 38.7 m. The slightly higher velocities of the upper densely welded tuff, compared to the lower densely welded tuf f , are explainable by the previously mentioned higher degree of fracturing within the latter. The low and high velocity zones («.1100 and 1800 m/sec) between 72 and 79 m correspond to mapping units "p" and "1". Bulk density profiles for Ue20u-3 and UZOu, using data from a lock-in density tool and laboratory tests, are compared to physical property units in Figure A2. Mapping unit "c" (57.6 to 60.7 m), a moderately welded ruff, and "p" (72.2 to 77.1 m), a consolidated reworked tuff , are clearly defined. The lower density values for the A1 ‘ I.’-‘/ '.!|‘r 1.. A": .k‘., saaua-I.> ‘., ‘UNIT U A2 TABLE A1 DESCRIPTION OF MAPPING UNITS BASED ON FIELD EXAMINATION OP U20u-2 CORE AND EJECTA DEPOSITS DEPTH (m) (Var) * (0-1.8) Soil zone, variable thickness 0-2 m, average 1 m. Fine grained, tan, contains fragments (2-6 cm) of caliche and desert-varnished tuff ( "11") . Ash-flow tuff, moderately to densely welded. Weathered portion of underlying unit; amount of oxidation and porosity decreases with depth. Grades downward from red to maroon, dark and dull when wet. A Ash-flow tuff, moderately to densely welded, devitrified, with vapor-phase crystallization. Contains 20-302 phenocrysts (1-4 mm) of feldspar and 5-102 fragments (2-15 In) of rhyolite and pumice. Grades downward from maroon to purple gray, dark and slightly dull when wet. Light color feldspars have rectan- gular habit producing a "salt and pepper" texture e *Variable thickness, not included in depths of other units. UNIT L P DEPTH (m) (8e5-9e8) (9.8-29.9) (29.9-33.2) A3 TABLE Al (cont'd) Ash-flow tuff, moderately welded. Fine grained with distinctive black pmnice fragments (15-35 mm), many with rectangular outlines, no feldspar phenocrysts. Medium gray. Soft, more porous than "R" and "U", very dark and dull when wet. Ash-flow tuff, densely welded, devitrified. Contains lO-ZOZ feldspar phenocrysts (1-5 mm) and 5-102 fragments of rhyolite and pumice. Pumice fragments (15-75 mm) are flattened and aligned horizontally producing an eutaxitic texture. Porosity less than "R" and "U", shiny when wet. Grades up to medium gray from purplish gray at base. Ash-flow tuff, moderately to densely welded, devitrified. Contains 20—252 phenocrysts (1-4 .) of feldspar and 5-102 fragments of rhyolite up to 10 -. Horizontal vugs of devitrified pumice up to 75 u with extensive flow foliation and partinge 2-10 In wide and 10-75 mm apart, results in a sheeted texture which grades up from "B". Porosity between "H" and "M". Medium purple grading downward to purple black at base. M 0 Y DEPTH (m) (33.2-35.7) (35e7-36e 7) (36s 7-38 e7) A4 TABLE Al (cont'd) Ash-flow tuff, densely welded, devitrified vitrophyre with no glass present. Contains 15-202 phenocrysts (1-4 m) of feldspar, 152 fragments ((4-25 -) of rhyolite and pumice. A few horizontal vugs near top as well as horizontal flow foliation. Porosity less than "L" from 35.7-34.1, slightly more porous below. Black. Ash-flow tuff, densely welded, devitrified vitrophyre with some glass present in black pumice fragments. Contains 15-202 phenocrysts of feldspar, 2: fragments of rhyolite and pumice. Numerous elongated vugs 1-5 m wide and up to 25 u long. Orange, grading to black at top. Contact with "I“ at base is sharp with rounded weathered fragments of rhyolite. Ash-flow tuff, moderately welded, devitrified vitrophyre with some glass present. Chemically altered. Yellow green to yellow brown. Becomes very porous toward base. DEPTH (m) (38.7-39.3) (39.3-41.1) (41e1-43 e 3) (49.1-53.0) TABLE Al (cont'd) Reworked ash-flow tuff, nonwelded, pumice rich, friable. Light yellow to yellow brown. Tan pumice fragments up to 20 mm containing small shards of black glass. Reworked ssh-flow tuff, nonwelded, pumice rich, friable. Orange yellow to reddish brown with depth, oxidized. Tan pumice fragments up to 20 mm.conteining small shards of black glass, some rhyolite fragments. Ash-fall tuff, nonwelded, pumice rich, friable, very fine grained. Grades upward from dark purple gray at base to lavender near top. Contains a tan (soil?) horizon several cm thick at top with limonitic staining. Ash-flow tuff, weakly welded, friable, fine grained. Contains 52 phenocrysts of feldspar and 10-202 equidimensional fragments of pumice some up to 10 cm. Contains zones of semi- welded, vitric, gray tuff. Ash-flow tuff, nonwelded to weakly welded. Transitional between g and "v". ‘Medium gray. gn_1__'r DEPTH Ln) v 63.0-57.6) c (57.6-60.7) 1 (60.7-61.9) v (61.9-72.2) 1’ (72.2-77.1) A6 TABLE A1 (cont 'd) Ash-f low tuff , weakly welded, vapor-phase altered? Contains 5-102 phenocrysts of feld- spar. Zones of moderately welded tuff with horizontally orientated vugs filled with feldspar and quartz crystals up to 25 -. Medium to purple gray. Ash-flow tuff, moderately welded, vapor- phase altered? Contains 5-102 phenocrysts of feldspar. Zones with horizontally orientated vugs filled with clear quartz and feldspar up to 25 -. Chocolate to reddish brown, oxidized. Reworked ash-flow tuff, friable, very fine grained, argillaceous, ch-ically altered, oxidized. Contains black pumice flakes up to 5 -. Reddish brown to orange. Ash-flow tuff, nonwelded, uniformly very fine grained . Small inclusions of orange pumice up to 5 -. Very few phenocrysts of feldspar. Light purple gray to white. Ash-flow tuff, very fine grain, nonwelded, reworked, argillaceous, oxidized. Some lithic (rhyolite) fragments up to 50 n. Yellowish orange to pale orange. DEPTH (m) (77 . l-78 . 6) (83.8-90.5) (90.5-93 .3) (93e3'95e7) A7 TABLE Al (cont 'd) Ash-flow tuff, lithic rich (rhyolite and pumice fragments up to 50 mm), friable to consolidated. Purple gray to yellowish brown to light tan. Reworked. Ash-fall (or flow) tuff, reworked, bedded, friable. Vitric pumice fragments up to 20 mm with feldspar phenocrysts. Some rhyolite fragments. Light gray to greenish white to bluish white. Ash-fall (or flow) tuff, friable to consoli- dated. Contains zo-zsz fragments (1-3 a.) of pumice. Buff to brownish gray. Ash-fall (or flow) tuff, friable to consoli- dated, fine grain, pumiceous, no fragments. Light gray to tannisb white. Ash-fall (or flow) tuff, reworked, bedded, pumiceous, friable. Contains 20—252 fragments (1-8 -) of pumice. Brownish gray to buff. Ash-flow tuff, reworked, bedded, partially welded with a few phenocrysts of feldspar and fragments of pumice up to 12 -. Tan to medium brown. UNIT DEPTH (m) (100.0-102.7) (103.3-112.2) T.D. - 112.2 m TABLE A1 (cont 'd) Ash-fall tuff, reworked, bedded, friable. Contains mostly pumice fragments. Similar to previous unit. Light gray to tan. Ash-flow tuff, reworked, argillaceous, partially welded. Few feldspar phenocrysts or rhyolite fragments. Brown to pale orange to yellow brown. Ash-flow tuff, moderately to densely welded, devitrified. Abundant dark gray to black horizontally aligned collapsed pumice fragments up to 75 mm with vugs containing vapor-phase crystals of feldspar and quartz. Fragments of rhyolite up to 25 mm. Feldspar phenocrysts 5-102. Light greenish gray to olive gray, local iridescent luster. DEPTH (m) A9 0 _ I I I T I I I I I I I I I I F I I I I q 25 __ UPPER DENSELY WELDED TUFF _ _ v =- 2217.3 1' 358.4 .../sec 4 L. V . Ex\ Velocity heel: of 42.7w *- 1 50 '- WEAKLY WELDED TUFF " " d b J .. V:1369.6 168.0 m/sec .. r- 1 ' NONWELDED TUFF " " '1 10° '- Velocify brook ot 103.6m '- q P u 125 ... LOWER DENSELY WELDED TUFF .. _ V82030.9i"279.5 III/sec ‘ b u 150 '- 4 1 1 i 1 1 L J l 1 1 l 1 1 L L l 1 L 100 05101520253035404550556065707580859095 Figure Al . TIME (msec) Downhole Velocity Profile for Ue20u-3 (From Tewes, 1970) DEPTH (m) A10 UPPER DENSELY WELDED TUFF 25 I—I- b _1 - + I— . 1 O F .7. 4 er”:& 1- . .1 \>.° 3' 5° "' v WEAKLY WELDED TUFF -‘ __.________._..‘.§ 5 g. '. NONWELDED TUFF ‘ O L 1 L L 1'. @1 l L l 1 1 1 l 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50 2.60 DENSITY (g/cm3) Figure A2. Bulk Density Profiles from In Situ and Laboratory Measurements for Ue20u-3 and U20u (From Tewes, 1970) DEPTH (m) 125 150 I. . — X .. .f ___}.F l 141 1"-A 1 1.11 1411 11 1.001.10 1.20 1.30 1.40 1.50 1:00 1.70 1.00 1.90 2.00 2.10 2.20 2.30 2.40 2.50 2.60 3 DENSITY g/cm All b . _— )3). q '<. ...—e/ NONWELDED TUFF P d x p e x e ' .s')‘ - .M 100$“? " .. LOWER DENSELY WELDED TUFF . In situ density from LRL clamp-in density tool - Ue200-3 I 0 It Bulk dry, as recovered, and bulk saturated 0 density measured on core from Ue200-3 I O I Bulk dry, as recovered, and bulk soturotsd density measured on cuttings from U200 (height of line is collection interval) k/ Figure A2. (cont'd) A12 top 15‘m of the lower densely welded tuff, compared to the upper Idensely‘welded tuff, are again due to the higher degree of fracturing in the former. The previously mentioned high variability of the non- 'we1ded tuff, particularly below 77 m, is apparent. With grain densities for all Schooner media ranging between 2.5 and 2.7 g/cc, 'variations in observed bulk densities are primarily a function of porosity and water content. Since porosity and water content so strongly affect the response of geologic materials to explosions (Butkovich, 1971), U20u and Ue20u-3 were vacuum drilled and samples tested on site, immedi- ately upon retrieval. Porosities generally follow the degree of ‘welding with values of 50 to 60% in the nonwelded tuff, 20 to 402 in the weakly welded tuff, and 10 to 20% in the densely welded tuff (Fig. A3). Fracturing in the upper portions of the densely welded tuffs result in slightly higher porosities. Mapping units "y", "m", and "1" (38.7 to 43.3 m), a nonwelded zone within the weakly welded tuff, are well defined. There are several zones with high, but unsaturated water contents within the weakly welded and nonwelded tuffs (Fig. A4). The top of the weakly welded tuff (mapping units "y", "m", and "1") and the middle and lower portions of the nonwelded tuff (mapping units "p" and "4" through "8") are highest in percent saturation (40 to 702). These zones are associated with contacts of the major ash-flows and are probably due to argillaceous soil zones underlying flows, to ‘baking at the contacts, or both (Ramspott, 1968). A13 ° 1 I T l l I 1 I I P . I I , ' r- I _ t l 0 Core from Ue201r-3 . I _4 II . I h I I Cuttings token from U200 ‘ I 'I I. I UPPER DENSELY vatoso TUFF ' I ' 1 P I 1 I _ I II o . I 50 P" I .1 I WEAKLY vatoeo TUFF DEPTH ( m) I l n. I ' q 0 O i F d 75 *- _ O P '1 ~ 1 - NONVIELDED TUFF O P i 100 - e _ {—.. 7 O l I p l d I :. ' LOWER osusstv vatoso run: D | q L_L&Illlll11.l‘ o 10 20 30 40 so 60 70 so 90 100 POROSITY (percentage of bulk volume) Figure A3. Porosity Profiles from Laboratory Measurements for Ue20u-3 and U20u (From Tewes, 1970) DEPTH (m) A14 0 - I I I | I l I I I. I UPPER DENSELY WELDED TUFF .- x = 5 e: X 3 005 range I to I6 ""9. 002 '0 0.3 ‘l 25 _ I I b'. I ' cl I . | T ' q I I I I -II 0 II o q 5° '1' VIEAKLY WELDED TUFF | 4 I- | q I i I I I a £9 % .. .' I. _ I 75 "' I g _1 r 0 I o . I. . ‘ I 'I ' NONWELDED 11mB 4 b I I L- . 0 o .4 100- O o‘ ._ ('3 I 4 1 O ' o o . D o o d .. | O 0 Values determined from core 0 _‘ 'I samples. Ue200‘3 O "I lo 0 “ '0 ~ 0 r- P l Values determined from cuttings. O .. I Ue200- 3 and U200 I - * I Loves ozuseu watoao' TUFF . - l o .. '50 b 1 1 1A 1 1 1 1 1 a 1 L 0 5 I0 IS 20 25 30 0 20 40 60 80 I00 FREE WATER (percent weight) SATURATION (percent) Figure A4. Free Water and Saturation Profiles from Laboratory Measurements for Ue20u-3 and mm: (From Tewes, 1970) A15 Representative core samples from each of the four physical property units were selected for high pressure testing by Stephens and Lilley (1970). Tests provided equation of state data for mathematical models used in the calculation of the Schooner event (Cherry and Petersen, 1970 and Terhune and Stubbs, 1970). Figure A5 presents loading and unloading pressuredvolume relationships and Table A2 lists typical physical property data. The two densely welded tuffs are similar, both exhibiting about the same amount of compressibility at 2.8 GPa (~14!) with little permanent compaction (~32) on unloading. Both the weakly welded and the nonwelded tuff exhibit twice the compressibility (30 and 362) and 4 to 9 times the permanent compaction (l3 and 272) because of their higher porosities. The lower permanent compaction ofthe nonwelded ruff is due to its higher water content. PRESSURE (GPa) A16 4.0 T F I I r Mama shoe = 2.306 g/cm3 (dry) I2I.9m sample LOWER DENSELY WELDED TUFF 3.0 *- Material 52.-Do =l-60 g/cm3 2.0 *- (wet) 9I-4m sample NONWELDBD TU FF I.0b 0.62 o l L }1 4.0 I I I I I UPPBR DENSELY WEI-DID TUFF Material 54“) = 2.37 g/cm3 3.0 '- 0 (dry) 12.5m sample ’ Material 53:00= I.“ g/cm3 2 0 _- (dry) 6.7m samde WEAKLY WELDED TUFF -— Loading - ‘— Unloading L0 — 0.62”? 0 r 1 —-d===-___. 0 40 0 45 0.” 0.55 0.60 VOLUME (ems/g) Figure A5. Loading and Unloading Pressure-Volume Curves for Four Representative Samples from Ue20u-3 (From Lessler, 1968) mun—H A17 page: mmé aé m.n m.m encu cué en.méné H.w¢.nlm.nc.n humane: was mung. .35 man c.~.n 6.3 can." on...“ 3.734 m.mdsluéo vandal—oz any .36 w.~ c.m~ m.» 2.: cc...” 8273.." 5.3153 3303 mass»: muss condom n~.c n.o e.n n.o coma om.~ am.~n-.~ ~.mmuo macaque Hanna use 8 8 3:3 A85 303 3 A.uouv usages: mongoose a sane owned «Han veadmuaao uaounou > use: and: huh—among gnauom sou—85.35 3a.“: Hanan nouns haw-nan menace Juno: Amadeus.“ SEMI glow ho muHEmcflm gHmE N4 and“. APPENDIX B APPENDIX B STEREOPHOTOGRAMMETRIC MAPPING, PROFILING, AND VOLUMETRIC COMPUTATIONS 1. Stereophotogrammetric Mapping The dimensional characterization of the Schooner crater and ejecta field was accomplished by aerial stereophotography and photo- grammetric analysis. The procedures, as they are commonly applied to cratering, have been previously discussed by Love and Vortman (1968) and Barron (1969). Briefly, after appropriate surveyed ground control is established, aerial stereophotography is performed both pre- and postshot. Pre- and postshot stereo models are optically constructed from rectified photo images and contoured in a stereoplotter to produce a pre- and postshot topographic map. By "subtracting" the preshot map from the postshot map, an isopach or difference map is produced expressing the net topographic change as a result of the event. Basic crater and ejecta field measurements are computed from the isopach map by planimetering and cross-sectioning. Figures 31, 32, and B3 present preshot, postshot, and isopach maps of the Schooner crater and continuous ejecta field. For Schooner, the aeria1.mapping was accomplished by American Aerial Surveys, West Covina, California (preshot December 68, postshot December 68 and January 69) at a range of photo scales from 1 in. - 280 ft* (1 cm I 33.6 m) to 1 in.'- 1200 ft (1 cm - 146.0 m). The photo *Photomapping and analysis performed in engineering units. Bl 32 A,» 21.... we in v ‘ \ x V J \ 5 u. Preshot Topographic Map of Schooner SGZ Area Figure 31. Postshot Topographic Map of Schooner Crater and Ejecta Blanket Figure 32. 0 5 0 L . 1 meters L . I? Figure 33 . Isopach Map of Schooner Crater and 81 ecta Blanket BS scale used in preparation of the topographic maps was 1 in. - 1000 ft (1 cm - 120.0 m) allowing a stereoplotter manuscript scale of 1 in. .- 100 ft (1 cm - 12.0 m) for contouring. The contour interval is 5 ft (1.5 m) for the lip and 25 ft (7.6 m) for the crater. Standards followed by the aerial mapping industry provide for a vertical positional accuracy of the contours such that 902 of the points are within 1 1/2 a contour interval of their true position while the remaining 102 are within 1 l contour interval. While there is no explicit horizontal positional accuracy, it is implied in the vertical positional accuracy. A general rule-of- thumb states that the planimetric position of any feature is within a distance equal to 1/60th of an inch (1/16th of a centimeter) of the stereoplotter manuscript scale. For Schooner this is 2.5 ft (0.75 m). The practical problems involved in delineating a zero thickness (outer "0" contour), especially when a 5 ft (1.5 n) contour interval is used, are substantial, hence portions of the outer "0" contour could be inaccurately positioned. With these limitations, the computed volumes are estimated to be conservatively within 52 of their true values and, if the outer "0" contour is accurately position (as the Reb contour is in the modified isopach map of Figure 24), within 2% (Barron, 1975). 2. Isopach Modifications During detailed field mapping of Schooner, the following modifica- tions were made to the original isopach map and are incorporated in the modified isopach map (Fig. 26): 36 (l) The 10 ft (3.0 m) contour was redrawn over portions of Rays 5 and 6, (2) A 5 ft (1.5 m) contour reflecting the isolated ejecta mass of Ray 11 was added, (3) The continuous ejecta boundary was mapped in the field and is labeled the lab contour. The lab contour replaces the outer "0" contour, previously determined by stereophotogranetric methods, for dimensional computations, (4) The continuous extent of ejecta blocks was mapped in the field and is labeled the Rb contour which is approximately a 1 ft (0.3 m) contour,- (5) A nonlinear thickness profile was constructed between the 5 ft (1.5 m) and the Rab contours. The first two modifications are self-explanatory; the last three are discussed below. By def inition, the 11.1, contour bounds the continuous coverage of the ground surface by ejecta; it was mapped directly in the field on the new 1973 aerial photography described in Appendix C. Desert-varnished rock fragments on the ground surface provided criteria for the contact. The outward continuous boundary for ejecta blocks (Rb) was also mapped in the field and approximates a 1 ft (0.3 m) contour. Both R» and Rh contours are plotted on the modified isopach map (Fig. 26). Except in the southeast quadrant, the fish contour generally tracks the outer "0" contour while exhibiting a better correlation to the Ray-Valley structure of the ej ecta blanket. This general agreement ’n finniffiflfi rave nvhr‘wr REV uvojncn (m 0.5) 37 VI 917’ (E\ A%LI nTUwiw Iqumei 9%: “nitnoETou Tuojcoo (n E.I) 37 E A (C) .Eusbf-E. an»: II vs": ‘0 (mi? NJ: n‘ Lnjjum anw YunLnuod njoeie euountjnoo SMT (f) TJjNU 9i; auntiwmv 1;03n03 Jflfi odT .TUOJHOD dad 9i: 2919451 :i .' I'.;‘:('r‘ : I’i lur’qna In It: ’.'*I InrrIrrrr—‘x Inl. "IIGHHI ‘I’I I’[ . :rt'. IHH - an“? In Inqmn. [hut-Iona”? 2', I a . I‘ I ,‘ "“‘ r I I r Inq'ilvv 'r‘ ' ': I null rtI uafa 1H IrraIa-a Dnunul IHHI atl'l (n) a I I). I r '.‘I!\Ir~wl uvrrr: TI qufz'AI 'vuulnu" (1'! Cult Inlnllc'l L‘l Farr. LIQII ,TU03HOD (m €.U) adj noumjad 5913u132n09 anv slllovc eeenioldj unanilnon A (C) .eruojnoo d9” ad: has (m 8.1) 3? k 915 991d? jarf 9N3 :7703nnnqu9-1198 91B anoijnollibom owj 33 '3 9n? .wnlnd Lsaauoaih (I u ‘50 aggrawos auounljrmn 91H eImuod 111031103 (,3)! 9d: .noljinilgl: v.‘ inf} (10 IJIBI‘I 9th) n1 ‘IIjiy3uiI) Le'uysn: Hit: 31 :53'n1fc) Y(l w'n;311us lulUlYI” -u3t Lorainusv-jvoaod .D xibueqnfi n1 qujvouqh vdqnvpojudq IEIWHfi (\Vl wan .393 :09 9M3 1o} 3&193113 bohivouq sonIvua bnuovg 9d) no u1n9m2n1 nognizuoo Lnudlnu an; B7 between the outer "0" and Reb contours implies that no major changes have occurred to the ej ecta blanket between the January 1969 serial mapping and the June-October 1971: field mapping. The lack of detailed agreement between the outer "0" contour and the Ray-Valley structure is probably due in part to the impreciseness in determining a zero thick- ness when photomapping. In addition, base surge deposits which initially covered the ejecta field out to a minimum of 1500 m consisted of silt-size tuff fragments which have been winnowed with time. The large discrepancy in the southeast quadrant between the outer "0" and ad, contours is believed due to heavier than average accumulations of base surge deposits. These resulted from the 62 topographic drop-off combined with the southerly surface winds. The standard method for computing volumes from an isopach map is to assume a linear fit between contours. During field mapping it was observed that between the 5 ft and Rob contours the decrease in ejecta thickness was not linear because of the bimodal size distribution of ejecta. An approximating profile between the 5 ft and Rab contours was constructed using the following linear segments with the constraint that the fish contour always terminates a profile: Contour Elevation 5 ft to Kb 5 ft to 1 ft RbtoRb-O-NOft lfttoO.5ft Rb + 100 ft to Rb + 200 ft 0.5 ft to 0.1 ft Rb + 200 ft to Rob 0.1 ft to 0 ft. . ‘31 ’ d ' , ' ~ . ‘r rt? ’ v' ‘ "" ‘ w , , . '. d‘ " . .,. .», "'t’ a » 1» I _s7 a. I . I‘ . . . . . . : q» ,. “we... . .4 .r .' ,.,. " a . . . . . . t . , . ,. , -I n l~. .’ .' l I ‘ , . l ' , - - a-e , - ,—.. ~ 1 , (I .. s I J ' ‘_ ' . . , l .- _ ._ - - . . . . , . . ,u , . . m . , . V‘{' v .. .1 I y' ... ., _a’ J —\ .l a u! I 'V ‘ 1 V . . . . . .r. -V 'I I. n J , ' _ .,. I J a q V I l "I e . I ’ 1 V " ’ V V '1 l .I . ‘. ' 1 . 4 . . I I «- w . ~ n,-., _I a , ... I ‘ '1 - / «4r B8 3. Volumetric Computations - Planimeter Method Volume of each ray was computed from the isopach map (Fig. 24) by determining areas between contours with a compensating polar planimeter and multiplying by the appropriate thickness. Two conditions were computed: (1) with a linear fit between the 5 ft (1.5 m) and outer "0" contours (as in the original photogrammetric computations), and (2) using the above discussed modified fit between the 5 ft (1.5 m) and new Reb contours. Totals for V5 and V1 using condition (1) were 2.22 higher and 2.92 lower than reported photo- grammetric values; these factors were applied to adjust all values computed using condition (2). The net effect of using condition (2) rather than (1) is a decrease of almost 102 in V1; the new apparent lip volume is 1,895,063 m3. Table Bl presents volumes of the apparent crater and lip for each ray, data are plotted in Figure 28. 4. Volumetric Computations - Profile Method Volumes of the apparent crater (Va), true crater (Vt), apparent lip (V1), and upthrust (Vu) were computed for each ray and 'valley from profiles constructed along their respective skewed axes (Fig. 24). True crater and upthrust profiles were constructed using available empirical formulae (Fisher, 1968). Cavity radius (RC) was determined using Closmann's (1969) equation: 10 11 TOTAL APPARENT CRAIER VOLUME V. (.3) B9 TABLE Bl SCHOOMER.APPARENT CRAIER.AND LIP VOLUMES FOR EACH RAY APPAREMT LIP VOLUME v1 (n3) 155,867 148,784 119,191 157,603 119,988 243,131 143,541 162,135 218,411 122,981 153,801 1,745,433 158,676 282,926 129,321 86,750 236,118 118,625 233,339 214,334 129,103 213,674 132,970 117,902 1,895,063 172,278 V1/Va 1.82 0.87 0.73 1.50 0.99 0.96 1.49 0.80 0.98 1.08 0.77 B10 where W a yield in KT E - Young's modulus in megabars u = shear modulus in megabars E'- average overburden density in g/cc h = DOB in meters. Using the material property data in Table A2, the resulting RC values are 46.9 m in the welded tuff below 103.3 m and 49.1 m in the non- welded tuff above. Since the lower hemisphere of the cavity is in the welded tuff, 46.9 m was used. Assuming a constant Rc below the ZP, true crater profiles were constructed by extending a parabola from Rc at 108 m (the ZP depth) to Rt at the preshot ground surface (for Schooner Rt - Ra)' Individual profiles were adjusted where the crater wall (true crater) was intersected. Upthrust profiles were constructed by connecting a straight line between the present position of the preshot ground surface observed along the crater (Fig. 26) to a point 1.5 m.above the original ground surface at 200 In (4.1.5 R3). A second straight line connects this point with a point on the original ground surface at 300 m.(~2.5 Ra)' This profile is typical of those observed on other buried explosive events (Fisher, 1968). Volumes were calculated with a computer program designed to accept profile data (range and depth values) and compute volume by the area-moment method (Lockard, 1974). The basic equations used are: Bll 2H Volume .- [AMOHCN’ 0 and Rn¢ AM - fr z(r)dr, 0 where AM - area moment r - range 2 - depth Ra¢ - radius of crater on a given radial, Volumes of annuli are summed using a straight-line fit between data points along a profile. Volumes presented in Table 32 and plotted in Figure 30 are for 360° and are, by design, maximized for each ray and minimized for each valley. Therefore, while relative volume comparisons are valid, absolute values require adjustment as in Table 2. 812 one.nfln.a ~mm.oon.~ una.o~n mum.nmn.~ mon.a~m omn.~oo.~ ono.om~.~ amn.o~o.a mos.omfi.a one.ooo wmn.n~m.~ nom.ooo.u nec.~mm.m 0 Anne > Ned.onn chm.mam cmo.~mm cou.mom cmc.chm ~mm.mom OMH.HHn oee.owm mom.¢um moo.mhm onH.wnm NHH.mon ewN.nN¢ a Anlv D Nam.mmH.N ou¢.~mo.~ mn~.wmd.d «mm.mnm.~ coo.~cN.H oom.uaa.~ ooo.weo.m mmm.~ce.a Nm5.wmn.fi mme.ssc.d woe.on~.~ nmm.ecw.a Hnm.sHH.c Anny; onm.oua.~ «Ho.oo~.~ ~on.~ofl.~ oao.no~.~ soo.onn.~ buo.aoo.u Hmo.ooo.~ ma~.oom.~ oNo.mhn.~ sam.ooo.~ nuo.nnm.~ non.o-.~ com.cmc.~ Anlvub Nn flflndu. wee.owh.n nme.dow.d cun.eoa.a nmc.wsm.d mam.oao.~ nud.mmo.u maw.aam.fi hon.ooo.~ ~we.ama.a ccw.omm.a muc.wda.d Naw.hmn.d who.wno.d Annen> coc.smw.n Hhc.aoo.c cmn.nwo.e Hmc.mcu.c cam.no¢.c oow.ccc.o oom.oo¢.e «mm.amm.e Nos.¢nm.e Hwa.man.o «ne.Hhh.c HOH.~we.o noc.onnnc An-vup ED 924 fig 8a “on mun—620330 Ban—AA; NH." a: 5:0 Boomum field «915 MMAAdfilh Nom.@oc who.m~¢ Haw.mmc mme.ode Hac.mnc ooH.~Hc sec.owm www.mnc wmh.omc va.wam mau.uwn woh.nme can.hhu Anlvjp one.wuh neo.wme.~ owH.Nno.H cca.¢hm.H own.wwn.m wan.om~.~ «NH.nwo.H nHN.Hoc.n sac.¢~o.a man.nnn.~ nmo.ons moa.nnc.m emn.ahm Amlv Ab «su.wn~.~ NH©.0HO.N oo~.ooa.fi. cmu.oe¢.d cnn.wmn.a woo.ome.a cou.°°o.d onn.non.d mmo.nno.H own.hus.u nnn.wns.d cmm.oon.a mwc.oon.d Ann—v up nom.non.u eon.oao.a onH.oHo.H ona.onn.a ~oa.een.a unn.nnn.a onn.ooe.a ~eo.ono.~ oom.~oo.a oeu.~oo.a an~.noa.a Hs~.anh.a nun.oow.a Anlv db To. 988 «a 5:5. sac.ass.n ono.nmc.n oom.osn.n cov.cwm.~ onu.nma.n wam.n~c.n cca.c~c.n wh¢.~cn.m nan.h~n.m «n~.nwn.m ~Nc.¢on.m mss.m¢n.m ~s¢.won.n Anne no HHI> HHLN OHI> AOHLu OOHLm floatu ngndfilhdm 1.5qu Afiiyclk 1...... Amnidnx Ame; < KENu,‘ «49.77325: III'I'1.6..I 1.08.701... II...“ I I APPENDIX C APPENDIX C GEOMORPHIC REGIMES, MAPPING PROCEDURES, AND DATA TABULATION l. Morphologic Regimes The initial distribution of blocks and fines followed by post- impact movement gives rise to a large variation of surface morphologies which have been grouped into seven distinct regimes applicable to ejecta, fallback, or both. These are described below. Blocky Areas (Ejecta and Fallback) Blocky areas contain a mappable set of blocks; i.e. sufficient number, size, and density of blocks such that the area can be delineated from surrounding areas. Rubble Areas (Ejecta) Rubble areas contain moderately to highly brecciated blocks with mean size usually less than 1/6 m and few, if any, in situ surfaces preserved. Many contain a high concentration of multiple secondary craters in varying degrees of obliteration and burial. Smooth Areas (Ejecta and Fallback) Smooth areas contain a sufficient quantity of fines to totally cover blocks or rubble. Smooth areas are subdivided into level areas (termed flats) and nonlevel areas (crests, fallback outcrops, topo- graphic highs, etc.). C1 C2 Drowned Areas (Ejecta) Drowned areas contain insufficient fines to completely cover underlying blocks or rubble. Degree of drowning varies depending upon size and number of blocks, topographic relief, and quantity of fines. while fines cover, to some extent, all surfaces out to the continuous ejecta boundary, drowned areas are designated only where fines significantly alter the surface morphology. Hummocky Areas (Ejecta) Hummocky areas exist where fines lightly cover portions of a rubble area producing a pockmarked or dimpled surface. Mixed Areas (Fallback) Mixed areas consist of mixtures of blocks and fines with no stratification. Transitional Areas (Ejecta) Transitional areas contain a discontinuous distribution of blocks covered by up to 15 cm of fines. Stratification is generally preserved. 2. Mapping Procedures General features of the Schooner crater and ejecta field have been discussed in Chapter IV. To provide a more detailed study of the surface morphology, highrresolution aerial photography was flown in 1973 by the U. S. Geological Survey and Williamson.Aircraft Co. of C3 Santa Barbara, California. Both black and white and color photography were obtained over a range of scales from 1 cm - 36.0 m to 1 cm . 6.0 m. Geomorphic mapping utilized the 1 cm - 18.0 m color photography. The continuous ejecta blanket was subdivided into specific areas, each delineating a singularly distinguishable surface feature in terms of morphology (blocky, rubble, smooth, drowned, hummocky, mixed, and transitional) and physiography (crest, valley, local topographic high, flat, etc.). Each area was assigned an average block size and a relative block areal density. These values are averages over each 'morphologic area and were determined by visual examination of aerial photographs with limited field verification. The degree of drowning of a particular area is reflected, in part, by the size and areal density values ascribed. Secondary craters and their ejecta fields, shocked pumice fragments, fused-glass fragments, and fallout deposits ‘were not mapped. Areas were mapped on individual photographs and then compiled using a survey control net established for this purpose. The survey net, accurate to 1 0.15 m, consisted of stations located every 10° at 610 m, every 20° at 366 m, and 40 stations spaced along the crater rim (see Chapter VI.A). In addition, stations were established every 152.4 I along a radial at 180° azimuth to 1524 m and approximately every 3 m along an excavated trench radially outward from the crater (see Chapter VI. B). Secondary control consisted of the established ground control for the earlier (1968-9) stereophotography, special topographic features, cultural features (roads, drill holes, bunkers, C4 etc.). and ancillary aerial and ground photographs. Crater mapping utilized the same photos, survey control, and mapping procedures. In addition, because of the large elevation difference from crater rim to floor (580 m) other photography were used. These included overheads, aerial obliques, and 35 mm slides taken from the rim and from within the crater. Over 550 separate areas were required to map the crater and ejecta blanket. These areas are numbered on the maps and listed in Table Cl, which also contains an example of the coding used. Data accumulated are presented in three geomorphic maps: (1) a surface feature map; (2) a block size map; and (3) a block areal density map. Maps 1, 2, and 3 are provided in the map pocket and reduced to page size in Figures 34, 35, and 36. 10. 11. 12. 13a. 14. 15. 16. 17. Se6e* Se6e Se6e Se6e Se6e Se6e Se6e Se6e Be3a SoGe So6e So6e SoGe SoGe 806e So6e SoGe BbZa SaSc merZa C5 TABLE C1 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. *See Geomorphic Regime Code at GEOMORPHIC REGIMES mer4c m-Bb3b ‘m-Bbe m-Bb4b mPBb3b SbSd mer4c ‘m-Bb4c m-Bb3b 816e Bb2a ‘m-Bb4c Bb3a Bb2a Bb2a Bb3a BbSb Bb3a Sa6e Bb3a end of Table Cl 38. 39. 39a. 39b. 40. 40a. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 50a. 51. 52. 53. Bb2a mer3c Sa6e Sa6e Bw Bb2a Sz6e Bb2a Sz6e Bb2a Sz6e SbSd Sz6e Sz6e Sz6e Sz6e Sa6c BbZa m-Bblb 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. m-Bb 2b Bb3a Bb3a Bbla Bb5c Sa6e Bb3a Sa6e Bbla Sa6e Bb4a mer3c Sb5d ‘m-Bb2b m-Bbe Bbla Sz6e Bb2a Bb3a Sa4a Sa6e Bb3c ‘merSd 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. C6 TABLE C1 (cont'd) Bb2a m-Bb2b SbSd Sz6e anblb m-Bb2b SbSd Bb2a Sz6e Bw Sa6e BbSa Bb4a Sz6e Bb3b Bbla Sz6e Sz6e Sz6e Sz6e Sz6e m-Bbla m-Bb3c BbSa 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 120a. 121. 122. 123. 124. Bb3a Bb2a merlc Bbla mer3c Bbla 'm-Bblb SbSd Bbla Sz6e Bbla Bbla Sa6e BbSa Sa6e Sa6e BbSa Sa6e Sa6e Sa6e Sa6d Bb3a Bbla Bb2a 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. Sb5d Bbla Sz6e Bbla Sz6e Sz6e SzGe Bbla Sz6e Bbla Bbla TABLE Cl (cont'd) 149. 150.’ 151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. C7 Sc6e Bc2a Sp6e . d-Bcp4b Bp2b Bp2b d-Bv3c ' Ss6e Sp6e Sh6e d-Rh5d SsGe Sf6e H6e d-RrSc d-RrSc d-Bg3c Rm4a C4c d-Ri4c d-Bg4b Ri4c d-Rr4a 173. 174. 175. 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. d-Rr3a d-Rr5c Rh5b C4d CSd d-Br2c Bg4b d-RrSd d-Rréb HGe CSc d-Rr5c d-Rr3b d-RrZa d-R4c d-Rr6d d-Rr4b d-RrSc d-Br5b d-Br4e d-Br3d d-Br4d d-Br3c d-Br2b 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. d-Bg4b d-C3c d-Br3b d-Bps4b d-Bp3a d-Bp13c Sps6e Sc6e d-B3d d-Bv2d Sps6e Sp6e St6e Sc6e d-Bp3c Sp6e d-Bde d-Bp2c d-Bp4c d-Bv3c d-Bp4c d-Bch d-Bp3b 221. 222. 223. 224. 225. 226. 227. 228. 228a. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. C8 TABLE Cl (cont'd) d-BrSc Ss6e d-Bv3b Bg4b Rr3a C4b CSc C4c 65c RrSa d-Rer B6e d-Rh6c d-Rh4b d-Rth Sh6e d-RrSc Rr4a d-RgSc Sh6e d-BrSd d-Bh5d RxSa Sf6e 244. 245. 246. 247. 248. 249. 250. 251. 252. 253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. Bc3d Sv6e Bc2a Bvla d-Bpr d-Bp3c d-Bp3d d-Bp2b Sl6e d-BhSd Sf6e $16e d-Bth Sh6e d-Bh4d d-RhSc d-Bh4c d-Bk5d d-Bk3b CSc d-Br4c C4c d-BrSd 268. 269. 270. 271. 272. 273. 274. 275. 276. 277. 278. 279. 280. 281. 282. 283. 284. 285. 286. 287. 288. 289. 290. 291. H6e d-RiSc d-RiSc d-RiSc d-Rr5c d-Rr3b d-Bg4d d-Bg3d d-Bg4b Sh6e d-Bh5c d-Bh4d d-Bh4d Sv6e Sh6e d-Bh3b Sl6e 3-Bp3c Sp6e Sc6e d-Bp5c Sp6e d-Bt3b d-Bt5c 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. 310. 311. 312. 313. 314. 315. C9 TABLE Cl (cont'd) Sv6e d-Bv4d d-Br4d d-Bva d-Bv3d d-Bp4c d-Bh3d Sf6e d-Bpr d-Bh5d d-Bh5d d-BhSd d-Br3c d-Bg4c d-C3c CSd CSc C4d Ri3b C4c CSc Br4b 03c 3:38 316. 317. 318. 319. 320. 321. 322. 323. 324. 325. 326. 327. 328. 329. 330. 331. 332. 333. 334. 335. 336. 337. 338. 339. d-Rr4c d-Rr3b d-Rr4c Bg4b RxSa RxSa Ri4a d-Bg4c d-Rr6c d-Rr6d d-Rh6c Sh6e d-Rm5b d-Rh6d d-Rh6d d-Bh5c Rr3a d-Bg4c d-Rr4c d-RrSd d-Bp2c Ss6e 340. 341. 342. 343. 344. 345. 346. 347. 348. 349. 350. 351. 352. 353. 354. 355. 356. 357. 358. 359. 360. 361. 362. 363. Sp6e Sc6e Btlb Btla d-Bv3c d-Bp2d Ssv6e d-Bv4c d-Bch d-Bv2c d-Bv3d d-Bg4c d-Br3a d-BrSc d-Br3b d-Br3d d-Br3d Rr5a d-Rr5d Bg4b Rr3b d-Br5d d-Rr6b d-Rr6d 364. 365. 366. 367. 368. 369. 370. 371. 372. 373. 374. 375. 376. 377. 378. 379. 380. 380a. 381. 382. 383. 384. 385. 386. C10 TABLE C1 (cont'd) Rr5a d-Rr3c d-RrSd Rr3a d-Rg4c Bg4b CSc C4b d-Rr4b d-Bg4c Bg4c d-Rr3b d-Bg4c d-CSd d-Rr5c Rr3a d-Rr4b d-Rr4b d-RrSd Ss6e d-Bs2a d-Bs3d Sp6e 387. 388. 389. 390. 391. 392. 393. 394. 395. 396. 397. 398. 399. 400. 401. 402. 403. 404. 405. 406. 407. 408. 409. 410. Sv6e d-Bpla Sc6e Bt3a Sps6e Sp6e Sc6e Sf63 Bpla Sp6e d-Bv3d d-Bt2c d-Bv4d d-Bv3b Sv6e Bp2a Sh6e d-Rh5c d-Rh5c d-Rh5c d-RrSc Hoe d-Rr5b Rr3a 411. 412. 413. 414. 415. 416. 417. 418. 419. 420. 421. 422. 423. 424. 425. 426. 427. 428. 429. 430. 431. 432. 433. 434. C4c Bg4b Bg4b C4b d-Bg4b C5d d-C3c Bg4c d-Rr6d Bg4b C4c d-RiSc CSc Rr3a d-Rr4b d-RrSd H6e d-jRixSa d-Bh3c Bla Bla Sh6e Sp6e Sc6e 435. 436. 437. 438. 439. 440. 441. 442. 443. 444. 445. 446. 447. 448. 449. 450. 451. 452. 453. 454. 455. 456. 457. 458. C11 TABLE Cl (cont'd) d-Bc3b Bc4a Bla d-Bp4c Bp2b d-Bp4c Bt2a Sp2c d-va4c Sc6e d-Bp5c d-pr3b d-Bp4c d-Bv3e Sp6e d-Bv3d Sf6e d-Bh3c d-Bp4c Sh6e d-RhSd d-Bh4c d-Rr6d d-Rh5c 459. 460. 460a. 461. 462. 463. 464. 465. 466. 467. 468. 469. 470. 471. 472. 473. 474. 475. 476. 477. 478. 479. 480. 481. d-Rh4b d-Rh5d d-Rh4b Bg4a d-Bg4b d-RiBa Rr3a Br3a C3b C4c d-Bg4c d-Rr4a d-Rr4b d-BgSc Sf6e Rr4b Bg4b d-RrSc n6e d-Rr4c d-RrSc Rr4a d-Rr6d d-Rr4c 791}? 482. 483. 484. 485. 486. 487. 488. 489. 490. 491. 492. 493. 494. 495. 496. 497. 498. 499. 500. 501. 502. 503. 504. 505. C4c‘ C4b C4b C5c Bg3b C4c C3c C4b Rr3a d-Rr5b H6e d-Rg4c d-Rh5c Shs6e d-CSd d-Rr4b d-RhSc d-Bp3c d-Bp4d d-Bp2c Sp6e Sp6e Bla d-Bv2d 506. 507. 508. 509. 510. 511. 512. 513. 514. 515. 516. 517. 518. 519. 520. 521. 522. 523. 524. 525. 526. 527. 528. 529. C12 TABLE Cl (cont'd) Btla A Bv2a d-Bv2a d-Bv3b d-Bv4d d-Bv3a d-Bv3c d-Bg4c d-Bv4d C4b CSc C4b Bg4b d-Rr5d C5d Hée d-Rr5c Rr4a CSc 05d C4c d-Rer d-Rg3b d-C5c 530. 531. 532. 533. 534. 535. 536. 537. 538. 539. 540. 541. 542. 543. 544. 545. 546. 547. 548. 549. 550. 551. 552. 553. Bg4b Rr3b d-Rr4a d-Rh5c 33b C3c d-Bg4c d-Rr4a H6e d-Rth d-Rh5c Bh4c d-Br3b Bh4c d-Br3d d-Bg3b d-Bh3c EGe d-Rh6c d-Rh6d d-BiSc Ss6e 554. 555. 556. 557. 558. 559. d-Bv3e d-Bv2b d-Bv2b d-Bp4b Sp6e Sc6e C13 TABLE c1 (cont'd) Example: (1) 459 (2) d-R (3) h (4) 4 (5) b (1) 459 C14 TABLE 01 (cont'd) GEOMORPEIC REGIME CODE (2) (3) (4) (5) : d-R h 4 b Map Area Code Morphology - Drowned, Rubble Physiography - Local Topographic High Average Block Size - 1/2 m Relative Block Areal Density - High MORPHOLOGY Blocky Area Rubble Area Smooth Area Bum-ocky Area Transitional Area Drowned Area Mixed Area Crater C15 TABLE Cl (cont'd) PHYSIOGRAPHY Ejecta Detritus Talus Ejecta Floor Soil Horizon (in situ + ejecta) wall Outcrop Crest Plat Ground Surface - Local Topographic High Isolated Unit Stream Cut Circumferential Valley Retarc Plateau Ray Terminus Slope Trough valley Secondary Crater C16 TABLE C1 (cont'd) BLOCK SIZE Number Average Code Block Length (m) I 2.2 2 1 1/2 3 l 4 1/ 2 5 5.1/6 6 Pines BLOCK.AREAL DENSITY Letter Relative Areal Density Code a Very High b High c Intermediate d Low e Fines APPENDIX D APPENDIX D MASS BALANCE COMPUTATIONS Mass balance relationships were calculated using procedures and formlations slightly modified from those developed by Carlson and Jones (1965). Figure Dl presents a sketch of an idealized crater and ej ecta field showing the various quantities involved and Table D1 lists densities, volumes, and computed masses. The basic equations are: Mt I'M. 'l-Mf Mn 'IMe +HI'. +MA MA -f (H8 andliu). H A is the mass that cannot be accounted for after fallback mass (Hf), ejecta mass (He), and cloud mass (Mk) have been subtracted from the true crater mass (Ht). H A is a function of compaction outside and below the true crater and upthrust above. The net mass lost to vaporization of material surrounding the device was significantly less than 11 of the true crater mass and is ignored in further discussions here. The various masses were computed in the following manner: (1) True Crater Mass (Ht) M1: " pt vt D1 ’1' ‘ ll- '7, re r I. I ."L/ I‘ {197’ f “ff. ‘4 . D2 anus—mounds: consume new: umuueuuesann seesaw An>L>ZnL>nnu§LSuES m3: 555 oz.mm_xlex 20.6mm IU4w>..—.Uwamm¢ >hpwzmo oz< £1340) .mm<1 whozma Qoz< .> .2 loans nuncahmaza =>=eu= hmDthn—D o S 2 .. 2 - E u <2 22505.0 92 29.5:on or use 33.. «ESE czar: no 2259. I 42 x . 3 one»: >m noun: >¢_v on n: 56mm. 33256an may-(m (FUN-d 131.x<1 020>um Omhfiommo m. h<1h 03040 2. a J<.¢wh<1&0mm(3 .l 2 Ir ‘ o> oe n 02 (huwaw macs-5:200 r motes... azaoao $2.23 NS D3 TABLE D1 SCHOONER VOLUME, DENSITY, AND MASS DATA Density Volume Mass (g/cc) (n3) (kg) True Crater 3,840,130 7,495,999,100 Upper Densely Welded Tuff 2.30 1,838,942 4,229,566,600 Weakly Welded Tuff 1.60 822,347 1,315,755,200 Nonwelded Tuff 1.50 911,035 1,366,552,500 Lower Densely Welded Tuff 2.20 260,594 573,306,800 Lower Honwelded Tuff 1.50 7,212 10,818,000 Missing Crater 3,976,908,140 Fallback l . 68 2 , 094 , 697 3 , 519 , 090 , 960 Upthrust 2.19 383,538 839,948,220 Ejecta Continuous 1.97 2,953,761,129 Discontinuous 2.30 247,219,822 Total 3,200,980,951 Cloud 74,959,991 Unaccounted 700 , 967 , 198 D4 True crater volumes were calculated, using procedures developed in Appendix B, incrementally for each of the 5 major units intersected by the true crater (Fig. 7). Density values are from Table A2. (2) Fallback Mass (Hf) H ID (V f f V) t - a True and apparent crater volumes are from Table 2. Fallback density was computed based on the relative proportions of the various units present and their assumed bulking characteristics. (3) Upthrust Mass (Mu) Upthrust volmne was calculated using procedures of Appendix 8 while density was estimated to be 952 of the average density of the upper densely welded tuff. (4) Cloud Mass (Mk) The mass of the Schooner cloud deposited beyond the continuous ejecta field was estimated to be 12 of the true crater mass based on analyses by Gudiksen (1970). (5) Ejecta Mass (Me) 1“a ' Mc"'Md -rn‘. 'r' fv"; 'ln- are f. ‘7“ 0" D5 The ejecta mass is the sum of the continuous ejecta mass (Me) and the discontinuous ejecta mass (Md). The continuous ejecta mass was calculated by integrating an average areal density profile from the average crater edge out to the average continuous ej ecta boundary and revolving this 360°. The equation is of the form Rob Mc - 21: f 80’) MD 1Ra . Similarly for the discontinuous ej ecta, from the average continuous ejecta boundary to the maximum recorded ejecta range, the equation is of the form a. Md - 21: f 50) MD Reb ° Schooner areal density data are presented with best fit straight lines in Figure D2. Data for the continuous ejecta field were derived from the ejecta portion of the average apparent lip profile (Fig. 23) using a density of 1.97 g/cc. This density was estimated from D6 ‘05 l- 1 I Ifilt' I I VIII] I T I IUTT'; I u 94 = 2.27 x lo” 0“?“ ’ 0 2.78Xlo'8 0'5“" -< L' 1 r i P '1 r J _ 7 J 103.. ‘5."°9°"'° D ‘6 r t * i b II '- -1 .- 4 \ I 1 g I- d E .. ob = 6.83 x 10” 0'2” . g A 1 457m Line " o m ‘0 :- 1. '1 S : 610... La... : - -1 < '- 4 E! ' é , T ‘3: " ol ‘ 0 1021 In Line " ‘0 — q E I : i + V 4' Averoge Profile e ‘ Io‘:- RJ Rmfid o .1 l- -I I v-n Rodiol , E " Circumferential - 10" if 1 . 21 h d i- q - '4 - a " '1 ‘0-3 I L 1 llLlll 1 1 1 LLllll J l 111. 10‘ 102 103 10‘ DISTANCE FROM SGZ (m) Figure D2. Ejecta Areal Density as a Function of Distance from 802 D7 observed ratios of blocks and fines in the trench and their corresponding bulk densities. Areal density data in the discontinuous ej ecta field are from volume measurements along R-1 and V-ll radials (Fig. 66) using the welded tuff block density of 2.30 g/cc. The previous two equations together with their boundary conditions give: -360 m 420 m 510 m 7 u - 2 c r [89) pan 4» [5501) non + [Scan nan 130 m 360 m 420 m and '900 m 2134 m M - 2 d r fgén)ndn+ [gums L510 m 900 m where 8(D) terms are given in Figure D2. Computed masses are presented in Table D1 and mass balance ratios in Table 4. REFERENCES REFERENCES Ahlers, E. 8., 1962, "Throwout Study of an Underground nuclear Detonation-Project Danny Boy", Illinois Institute of Technology, Defense Nuclear Agency Report,POer814. Andrews, R. J., 1975, "Origin and Distribution of Ejecta From Near- Surface Laboratory-Scale Cratering Experiments", University of Dayton Research Institute, Air Force weapons Laboratory Report, AFWL-TR-74-314. Baldwin, R. B., 1963, "The Measure of the Moon", University of Chicago Press. Butkovich, T. R., 1971, "Influences of Water in Rocks on Effects of Underground Nuclear Explosions", Journal of Geophysical Research, Vbl. 76, no. 8. Butkovich, T. R. and Lewis, A. E., 1973, "Aids for Estimating Effects of Underground Nuclear Explosions", Journal of Geophysical Research, Vol. 76, No. 8. Butkovich, T. R. and Lewis, A. E., 1973, "Aids for Estimating Effects of Underground Nuclear Explosions", Lawrence Livermore Laboratory, UCRL-50929 (Rev. 1). Carlson, R. H. and Jones, C. D., 1964, "Project Air Vent - Ejecta ‘Distribution Studies", The Boeing Company, Report-D2-90575. Carlson, R. H. and Jones, C. D., 1965, "Distribution of Ejecta from cratering Explosions in Soils", Journal of Geophysical Research, ‘Vol. 70, No. 8. Carlson, R. H. and Howell, R. T., 1970, "Ejecta from Single-Charge cratering Explosions", The Boeing Company, Sandie Laboratories Chabai, A. J., 1962, "Radioactive Tagging of Crater Ejecta", Chapter 5, Project Stagecoach, Sandie Laboratories Report, SC-4595(RR). Chabai, A. J., 1965, "On Scaling Dimensions of Craters Produced by Buried Explosives", Journal of Geophysical Research, Vol. 70, No. 20. *Cherry, J. T., 1967, "Computer Calculations of Explosion - Produced Craters", International Journal of Rock Mechanics and Mining Science, ‘vol. 4. R2 Cherry, J. T. and Petersen, F. L., 1970, "Numerical Simulation of Stress Wave Propagation from Underground Nuclear Explosions", Proceedings-Symposium on Engineering with Nuclear Explosives, The American Nuclear Society, CONE-700101. Christiansen, R. L. and Noble, D. C., 1968, "Geologic Map of the Trial Ridge Quadrangle, Nye County, Nevada", Geologic Quadrangle Map GQ—774. Circeo, L. J., 1969, "Nuclear Excavation: Review and Analysis", Engineering Geology, Vol. 3. Closmann, P. J., 1969, "On the Prediction of Cavity Radius Produced by an Underground Nuclear Explosion", Journal of Geophysical Research, V. 74, No. 15. Danielson, G. E., 1975, "Our Present View of Mercury and Venus", Proceedings of the Sixteenth General Assembly International Union of Geodesy and Geophysics, U.S. National Report for 1971-1974. Day, W. C., 1972, "Craters as Engineering Structures”, U.S. Army Engineer Waterways Experiment Station, Miscellaneous Paper E-72-2. Diehl, C. H. and Jones, C. H., 1964, "A Tracer Technique for Cratering Studies", Journal of Geophysical Research, Vol. 70, No. 2. Fisher, P. R., 1968, "Engineering Properties of Craters", U.S. Army Engineer Nuclear Cratering Group, PNE-5012. Fransden, A. D., 1970, "Engineering Properties Investigations of the Cabriolet Crater", U.S. Army Engineer Nuclear Cratering Group, PNE-957 e Freeberg, J. R., 1966, "Terrestrial Impact Structures - A Bibliography", U.S. Geological Survey Bulletin 1220. Gault, D. E., Quaide, W; L., and Oberbeck, V. R., 1968, "Impact Cratering Mechanics and Structures", in Shock Metamorphism of Natural Materials, Mono Book Corporation, Baltimore. Gudiksen, P. E., 1970, "Mass Concentrations and Particle Size Distributions as a Function of Time Within a Nuclear Cratering Cloud", University of California Lawrence Radiation Laboratory, UCR1950844. Hansen, S. N3. et al., 1964. "Recommended Crater Nomenclature", Geophysics, Vol. 29, No. 5. Barron, W. J., 1969, "Large Scale Photogrammetry in an Explosive Testing Program", Proceedings of the Convention of the American Society of Photogrammetry and American Congress on Surveying and Mapping. 1L3 Barron, W. J., 1975, "Personal Communication", Limbaugh Aerial Mapping Division of Bovay Engineers, Albuquerque, N.M. Hasler, J. W., 1965, ”Preliminary Report on the Lithology of Drill Hole UeZOJ, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies I-35. Hasler, J. W. and Byers, F. M., 1965, "Preliminary Report on the Lithology of Pahute Mesa Drill Hole No. 2, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies 1-39 e Benny, R. W. and Carlson, R. H., 1968, "Distribution of Natural Missiles Resulting from Cratering Explosions in Hard Rock", Annals of the New York Academy of Sciences, Vol. 152, Art. 1. Benny, R. W., 1970, "Schooner Ejecta Studies", Proceedings-Symposium on Engineering‘with Nuclear Explosives, The American Nuclear Society, CONF-700101. Hess,‘W. N. and Nordyke, M. D., 1961, "Throwout Calculations for Explosion Craters", Journal of Geophysical Research,Vol. 66, No. 10. Jenkins, E. C., 1969, "Summary Geologic Report on the Ue20p Exploratory Hole, Area 20, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies-75. Jenkins, E. C., 1969, "Summary Geologic Report on the U20p Emplace- 'ment Hole, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies-75 (Supplement 1). Johnson, R. B., 1962, "Effect of Geologic Factors on Cratering Experiments in Basalt-Buckboard Mesa Test Site, Nevada", U.S. Geological Survey Technical Letter: Area 18-1. Johnson, S. W., Galbraith, B. G., Bessert, G. C., Henny, R. W., and Swift, H. F., 1971, "Motion of Ejecta from.Sma11 Cratering Events", Abstract-52nd Annual Meeting of the American Geophysical Union, EOS Transaction, Vol. 52, No. 4. Lessler, R. M., 1968, "Schooner Preshot Analysis", Lawrence Radia- tion Laboratory, UCRL-50530 (Rev. 1). Lockard, D. M., 1974, "The LAUNI 2 Code: A.Program for Calculating Crater Volume", Air Force Weapons Laboratory, AFWL-TRP73-265. Love, G. C. and Vertman, L. J., 1968, "Photogrammetric Techniques .Associated with Model Studies of EarthrMoving Explosions", Preprint, .American Society of Civil Engineers National Meeting on Transporta- tion Engineering. R4 Lutton, R. J. and Girucky, F. E., 1966, "Project Sulky Geologic and Engineering Properties Investigations", U.S. Army Engineer Waterways Experimental Station, PNE-720. Moore, H. J., 1976, "Missile Impact Craters (White Sands Missile Range, New'Mexico) and Application to Lunar Research", Geological Survey Professional Paper 812-B. Moore, H. J., 1977, "Nevada Test Site Craters Used for Astronaut Training", U.S. Geological Survey Professional Paper, In Print. Mutch, T. A. and Head, J. W., 1975, "The Geology of Mars: A Brief Review of Some Recent Results", Proceedings of the Sixteenth General Assembly International Union of Geodesy and Geophysics, U.S. National Report for 1971-1974. Nbrdyke, M. D., 1961, "Nuclear Craters and Preliminary Theory of Mechanics of Explosive Crater Formation", Journal of Geophysical Research, Vol. 66, No. 10. Nugent, R. C. and Banks, D. C., 1966, "Project Danny Boy-Engineering Geologic Investigations", U.S. Army Engineer Waterways Experiment Oberbeck, V. R., 1971, "Laboratory Simulation of Impact Cratering with High Explosives", Journal of Geophysical Research, Vol. 76, No. 23. Orkild, P. P., 1969, "Summary Geologic Report on the U20u Emplace- ‘ment Hole, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies I-35 (Supplement 1). Orkild, P. F., Sargent, K. A., and Snyder, R. F., 1969, "Geologic Map of Pahute Mesa, Nevada Test Site and Vicinity, Nye County, Nevada", U.S. Geological Survey Miscellaneous Geologic Investigation mp 1-567 e Piekutowski, A. J., 1974, "Laboratory-Scale High-Explosive Cratering and Ejecta Phenonenology Studies", University of Dayton Research Institute, Air Force Weapons Laboratory Report, AFWL-TR-72-155. Post, R. L., 1974, "Ejecta Distributions from Near-Surface Nuclear and HE Bursts", Air Force Weapons Laboratory, AFWL—TR974-51. Purtymun, W. D., Harrill, J., and Rush, F. E., 1969, "Geologic Data for U20u Satellite Holes 1, 2, 3, and 4, and Studies of the Orienta- tion of Joints in the Thirsty Canyon Tuff, Area 20, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Open File Report. Ramspott, L. D., 1968, Internal'Memorandum, University of California Lawrence Livermore Laboratory, Livermore, CA. R5 Richards, W. D. , 1964, "Geologic Study of the Sedan Nuclear Crater", Lawrence Radiation Laboratory, PNE-240. Roddy, D. J., 1968, "The Flynn Creek Crater, Tennessee", in Shock Metamorphism of Natural Materials, Mono Book Corporation, Baltimore. Roddy, D. J ., 1970, "Geologic Studies", Operation Prairie Flat Symposium, DASA-2377, Vol. I. Roddy, D. J., 1973, "Geologic Studies of the Middle Gust and Mixed Company Craters", Proceedings of the Mixed Company and Middle Gust Results Meeting, Defense Nuclear Agency, DNA-3151. Roddy, D. J., Boyce, J. M., Colton, G. W., and Dial, A. L., 1975, "Meteor Crater, Arizona, Rim Drilling with Thickness, Structural Uplift, Diameter, Depth, Volume, and Mass Balance Calculations", Proceedings-~Sixth Lunar Science Conference. Rohrer, R. F., 1972, "Schooner Surface Motion and Vented-Gas Temperature Measurements", University of California Lawrence Livermore Laboratory, UCRL-51181. Sakharov, V. N., Kolesnikov—Svinarev, V. 1., Nazarenko, V. A., and Zabidarov, E. 1., 1959, "Local Distribution of Earth Thrown Up by Underground Explosions", Doklady Akad. Nauk., Vol. 125, No. 2. Sargent, K. A. and Jenkins, E. C., 1968, "Summary Geologic Report on the U320u-l and Ue20u-3 Drill Holes, Area 20, Pahute Mesa, Nevada Test Site", U.S. Geological Survey Technical Letter: Special Studies-68. Shackelford, T. J ., 1971, "Crater Stability Under the Influence of Large Seismic Motions", U.S. Army Engineer Nuclear Cratering Group, Sherwood, A. E., 1967, "Effect of Drag on Particles Ejected During Explosive Cratering", Journal of Geophysical Research, Vol. 72, No. 6. Shoemaker, E- M. . 1963. "Impact Mechanics at Meteor Crater, Arizona", in The Solar System, Vol. IV, The Moon, Meteorites, and Comets, University of Chicago Press. Short, N. M., 1964, "Project Danny Boy: »‘ the Definition of True Crater Dimensions by Postshot Drilling", Lawrence Radiation Laboratory, Short, N. M. and Bunch, T. E., 1968, "A Worldwide Inventory of Features Characteristic of .Rocks Associated with Presumed Meteorite Impact Craters", in Shock Metamorphism of Natural Materials, Mono Book Corporation, Baltimore. R6 Shreve, R. L., 1968, "The Blackhawk Landslide", Geological Society of America, Special Paper 108. Sneed, E. D. and Folk, R. L., 1958, "Pebbles in the Lower Colorado River, Texas-a Study in Particle Morphogenesis", Journal of Geology, Vol. 66. " Stephens, D. R. and Lilley, E. M., 1970, "Loading-Unloading Pressure Volume Curves for Rocks", Proceedings-Symposium on Engineering with Nuclear Explosives, The American Nuclear Society, CONF-700101. Stoffler, D., Gault, D. E., Wedekind, J., and Polkowski, G., 1975, "Experimental Hypervelocity Impact into Quartz Sand: Distribution and Shock Metamorphism of Ejecta", Journal of Geophysical Research, Vol. 80, No. 29. Strohm,‘W. E., Ferguson, J. S., and Krinitzsky, E. L., 1964, "Project Sedan-Stability of Crater Slopes", U.S. Army Engineer Waterways Experiment Station, PNE-234F. Terhune, R. W. and Stubbs, T. F., 1970, "Nuclear Cratering on a Digital Computer", ProceedingsuSymposium on Engineering with Nuclear Explosives, The American Nuclear Society, CONE-700101. Terhune, R. W. , 1976, "Personal Comnication", Lawrence Livermore Laboratory, Livermore, CA. * Tewes, H. A., 1970, "Results of the Schooner Excavation Experiment", Proceedings-Symposium on Engineering with Nuclear Explosives, The Anerican Nuclear Society, CONF—700101. Vaile, R. B. , 1961, "Pacific Craters and Scaling Laws", Journal of Geophysical Research, Vol. 66, No. 10. Vesic, A. S., Boutwell, G. F., and Tai, T. L., 1967, "Theoretical Studies of Cratering Mechanisms Affecting the Stability of Cratered Slopes", Duke University School of Engineering, Soil Mechanics Series No. 11. vesic, A. 8., Ismael, N. M., and Bhushan, R., 1972, "Cratering in Layered Media", Duke University School of Engineering, U.S. Army Engineer Waterways Experiment Station Report, E-72-3l. Vortman, L. J. , 1969, "Ten Years of High Explosive Cratering Research at Sandia Laboratory", Nuclear Applications and Technology, Vol. 7. Vortman, L. J ., 1970, "Nuclear Excavation", in Education for Peaceful Uses of Nuclear Explosives, University of Arizona Press. '} . ‘A if N I28 c ké/f .0. 7 .. ... w ,(m" . ‘ !' gum}! 4? W'ATHI b; v~~" ." arias! ‘ ’.;"Il"A 015T . " .L' .31 , r . r? atheism ' . _ ' ' ' I) 17351119 - .-“ .“ .noarfi: . > 1 ‘ 'rr‘l‘if'fil’D 3°, " '.—"-UW .azidusfi ' . “9‘.- 90‘1"! Q “ v 'i'rzP'ffi’r" .OW .AL) ,9 go‘ .. r " “1,.uaeif , », ' ~w’i ”(I y-"t . , ' 'v-lr."')_ .waioo‘r ‘ 1‘! :11 1981”] ‘ .TOV , '-r ..'. .3 .I ' arm: 2:11:1de ' r. rfl’)” '{313 ». :1: .‘flb‘ ..M In a . p}; "‘?'r—'ISVJ’H", , z" rung). nominal ’ L f ‘ “0 was? 1191'" r - ’.:’,r~:‘ ‘13:»,th ' fut" 7391M" ‘fi‘f 'vtr\jf',1 .8071“ . w 3 ”1.3.4 '1' H.‘ ‘ —- . . - I \. ”it ‘ o , e 5.4 1