ENGLACIAL STRUCTURES OF THE VAUGHAN LEWIS ICEFALL,
AND RELATED OBSERVATIONS ON THE
JUNEJIU ICEFIELD, ALASKA. 1957 - 19.69

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY
LOUIS RUTHARDT MILLER
1970

 

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Michigan indie U ul‘V'JIJJ)

East Lansing, Michiqrn

 

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University

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ABSTRACT

ENGLACIAL STRUCTURES OF THE VAUGHAN LEWIS ICEFALL,
AND RELATED OBSERVATIONS ON THE JUNEAU
ICEFIELD, ALASKA, 1967-1969

BY

Louis Ruthardt Miller

Wave-ogives are defined as the three-dimensional
surface wave forms found at the base of many glacial ice—
falls. The morphogenesis of these wave forms is in dis-
pute. Two main theories exist to explain their origin:
(1) The ablation theory-~greater ablation during the sum-
mer months forms a trough and the increased accumulation
during winter months causes a wave-crest. (2) The com-
pression theory-—wave-ogives result from a longitudinal
compressive thickening at the base of an icefall, thus
forming a wave during late summer presumably when com-

pression is at its greatest.

Measurements of englacial structures on the Vaughan
Lewis Glacier, Alaska, including steeply dipping tectonic
foliation and transecting thrust surfaces, plus supple—
mental surface movement surveys obtained during the years
1967-1969 indicate that a longitudinal compressional stress

does exist in the ice apron sector at the foot of the

Louis Ruthardt Miller

icefall, and indeed in the basal ice of the lower half of

the icefall itself. This interpretation reinforces the

argument for compression thickening. It does not, how-

ever, rule out the possibility of at least some accentu—
ation of surface bulges in the apron area by ablation,
though this is considered to be a subordinate factor in

basic genesis of these striking surface features.

ENGLACIAL STRUCTURES OF THE VAUGHAN LEWIS ICEFALL,
AND RELATED OBSERVATIONS ON THE JUNEAU

ICEFIELD, ALASKA, 1967—1969

BY

Louis Ruthardt Miller

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geology

1970

ACKNOWLEDGMENTS

This study was made possible through financial and
material support from the Foundation for Glacier and En—
vironmental Research (FGER) via the Juneau Icefield Re-
search Program (JIRP) in the years 1967, 1968, 1969, and
research grants made through the Alaska Glacier Commemora-
tive Project of the National Geographic Society, Washington,
D.C. Assistance was also rendered by the Glaciological and
Arctic Science Institute of Michigan State University and
the U.S. Forest Service with the loan of surveying equip-

ment.
It is with sincere appreciation that thanks are

extended to Professor Maynard M. Miller for his stimu-
lation, encouragement, enthusiasm, and guidance both in
the field and during preparation of this manuscript.
Thanks are also extended to Drs. Hugh F. Bennett,
Robert W. Little, and James W. Trow for helpful sug-
gestions and critical review of the manuscript as the
other members of the writer's thesis committee.

Deep appreciation must also be extended to many

of the members of JIRP, too numerous to mention, who have

helped logistically. It is only through the assistance

ii

of these many selfless individuals that a topic of this
magnitude could be approached and these results accom-
plished in the main summer field seasons of 1968 and 1969.
It is especially true in field research on glaciers that

one's success depends on the close help and cooperation

of one's colleagues. This is because not only must one

work closely with them, but also one must live with and
learn from them at times when one's life is wholly de—

pendent on their concerns and their abilities. For this

aspect as well, special thanks are extended to my field

associates Dr. Alfred C. Pinchak, William Lokey, and

John Schutt.
Thanks are also extended by the writer to his

brother, William M. Miller, and the writer's wife, Karin,

for help in computer programming.

iii

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I ‘IVI

TABLE OF CONTENTS

Section
LIST OF TABLES . . . . . . .

LIST OF FIGURES. . . . . .

INTRODUCTION AND PHYSICAL SETTING. . .

METHOD AND AREAS OF RESEARCH . . . .

INVESTIGATION OF THE VAUGHAN LEWIS GLACIER.

Observations in the Crestal Névé . .
Investigation of the Icefall Zone. .

Morphogenetic and Structural Features in

the Wave—Ogive Zone. . . .
Crevasse Observations. . . .
Surface Movement, 1967-1969. . . .

Mass Transfer and Theoretical Considerations

SUMMARY OF RESULTS AND CONCLUSIONS . .

SUGGESTED ADDITIONAL INVESTIVATION . .

REFERENCES . . . . .
TABLES. . . . . . . . .
APPENDICES

Appendix

A.

on Cleaver West of Camp 18 . .

Data 1, 23 July 1968

Part 1.
Data 2, 29 July 1968 .

iv

Vaughan Lewis Glacier Computer Program
Input Data, Taken from Survey Points
FFGR #5 (Upper) and FFGR #4 (Lower)

Page
vi

vii

l7

l7
18

20
38
43
57
61
64
68

73

73

Section Page
Part 2. Data 3, 8 August 1968
Data 4, 15 August 1968
Data 5, 25 August 1968 . . . . 74
Part 3. Data 6, 7 September 1968
Data 7, 27 July 1969
Data 8, 1 August 1969 . . . . 75
Part 4. Data 9, 23 August 1969
List of False Data, Substituting
for Blanks for Computer Pro-
gramming. . . . . . . . . 76
B. Laboratory Simulation of Vaughan Lewis
Icefall Showing Mechanically Developed
Wave—Bulges in a Visco—Plastic Material
in a Scale Model . . . . . . . . . 77
GLOSSARY OF SELECTED GLACIOLOGICAL TERMS . . . . 81

LIST OF TABLES

Fortran Computer Program, Vaughan Lewis

Glacier Horizontal Movement . .

Movement Computed for the Periods 23 July
l968--29 July 1968 and 29 July 1968--

8 August 1968. . . . . . .

Movement Computed for the Periods 8 August
1968-~15 August 1968 and 15 August 1968—-

25 August 1968 O O O O O 0
Movement Computed for the Periods 25

August l968--7 September 1968 and
7 September 1968--27 July 1969 .

vi

Page

68

70

71

72

LIST OF FIGURES

Figure Page
1. Map of Southeastern Alaska . . . . . . 2
2. Location Map of the Juneau Icefield . . . 3
3. Vaughan Lewis Icefall. . . . . . . . 4
4. Pyramid Pylon Marker Placed at Stake No.

15 on 6 August 1968. . . . . . . . 13
5. Stake No. 15 Area 26 July 1969. . . . . 13
6. Upper Herbert Glacier Mosaic . . . . . 16

7. Sketch Map of Wave-Ogive Crests on the
Vaughan Lewis Glacier as Observed in
August 1968 O O O O O O O O O O 21

8.3 Diagrammatic Reconstruction of Surface
Detail on Longitudinal Traverse Across

Wave-ogives K, L, and M o o o o o o 23

9. Tectonic Folia in Vertical Wall of Stream
Channel. . . . . . . . . . . . 25

10. Tectonic Folia in Non—Vertical Crevasse
wall. 0 O O O I O O O O O O O 25

11. Distribution of Tectonic Foliation Within
Wave-Ogive J, B-Sector. . . . . . . 28

12. Distribution of Tectonic Foliation Within
Wave-Ogive J, a-Sector. . . . . . . 28

13. Distribution of Tectonic Foliation Within
Wave-ogive ‘K' B‘SGCtor. o o o o o o 29

14. Distribution of Tectonic Foliation Within
Wave-Ogive K, a-Sector. . . . . . . 29

vii

Figure page

15. Distribution of Tectonic Foliation Within

Wave-Ogives L, M, N Combined, B—Sector . . 30
16. Distribution of Tectonic Foliation Within

Wave-Ogives L, M, N Combined, a—Sector . . 30
17. Profile Diagram of Tectonic Folia of

wave-Ogive J. a o o o o o o o o o 33
18. Ogive Section of the Vaughan Lewis Glacier . 4o
19. §§_Echelon Crevasses. . . . . . . . . 4o

20. Longitudinal Profile of Lower Icefall of
the Vaughan Lewis Glacier . . . . . . 42

21. Plotted Results of Horizontal Surface Move-

ment Below the Vaughan Lewis Icefall. . . 45
22. Kaolin Model of the Vaughan LeWis Icefall. . 52
23. Profile View of Wave—Ogive K . . . . . . 53

viii

INTRODUCTION AND PHYSICAL SETTINGl

"Ogives have puzzled generations of alpinists and
their close study is long overdue, especially as their
elucidation should advance considerably our knowledge of
glacier movement." These are the words of William Vaughan
Lewis (1956), of Cambridge University, England, whose name
this glacier bears.

The Vaughan Lewis Glacier on the Juneau Icefield
(Figures 1 and 2) provides a classic example of the type
of features Professor Lewis described. The Vaughan Lewis
Glacier (Miller, 1963a), is considered to be a typical,
climatologically-controlled normal discharge type of
glacier (M. M. Miller, 1969, personal communication). It
has been used since 1961 as a prototype on the Juneau Ice—
field, Alaska for study of glacial behavior and movement
within an icefall (Figure 3).

The Vaughan Lewis Glacier is located in Southeast-
ern Alaska at latitude 58° 49'N., longitude 134° 17'W. Its
source area or névé lies immediately southeast of Mt.

Ogilvie a boundary peak of the Northern Boundary Range

 

lV. glossary on page 81 for definition of glacio-
lOgical terms used in this presentation.

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in the high Coast Mountains between northern British
Columbia and Alaska.

The Vaughan Lewis Glacier (Figure 3) is of the
glaciothermally (geophysically) temperate type with the
main structures of concern in this study (surface wave
bulges, wave—ogives and ogives) all lying downvalley from
the mean névé-line of the 1960's. In the three years of
this study the névé—line at end of summer attained an
average elevation of 1277 m (4200 ft). It was as high
as 1400 m (4600 ft) in the unusually warm and dry summer
of 1968. In the unusually cool and stormy summer of 1969,
however, it remained as low as 1160 m (3800 ft).

This icefall and glacier is fed by a névé at a
mean altitude of 1680 m (5600 ft) with a total accumulation

2 (8.6 miz). The icefall is

area of approximately 26 km
approximately 1 km (0.6 mi) wide, and drops 500 m (1500 ft)
at an angle of descent varying between 24° and 40° (Figure
3). The ice depth at the base of the icefall has been
measured at somewhere between 180 m (600 ft) and 210 m

(700 ft) in depth (Kittredge, 1967; Prather, 1969, per-
sonal communication based on 1968 seismic data).

The wave-ogive area lies on the downvalley apron
of the icefall where the lower Vaughan Lewis Glacier meets
two other main valley glaciers. Adjacent to this icefall
and on the south is an "unnamed" glacier. Immediately

adjacent and to the north is the Gilkey Glacier. The

framing position of these glaciers is shown in Figure 7,

page 21. Each coelesces and flows as one continuum down-
valley to a terminal position 15 km (9 mi) west southwest

of the icefall.

METHOD AND AREAS OF RESEARCH

On the Juneau Icefield the Foundation for Glacier
and Environmental Research has constructed a number of
permanent research stations in connection with its long-
term Juneau Icefield Research Program. These are aluminum-
covered and usually well insulated frame structures which
serve as main centers from which field parties obtain
scientific data regularly each summer, including daily
meteorological information at the main stations (Figure 2).
The research done on the Vaughan Lewis Glacier, which is
discussed in the present report, was carried out during
the years 1968 and 1969. Some reconnaissance observations
by the writer were also made in the summer of 1967. In
all of this, Camp 18 and Camp 18B, and to a lesser extent,
Camp 19 served as the main research centers. Camp 18B
was a tent camp from which most of this research was con-
ducted. Here two nylon mountain tents and related tem-
porary field facilities, including a meteorological
shelter, portable radio, etc. were used. Camp 18 is a
more permanent installation, comprised of several build-

ings. This was used as the radio relay station and

permanent logistics base, and as such was revisited about
once a week to replenish needed food and supplies at Camp
18B.

Camp 19 was also employed. This camp has a single

2 (12 ftz)

wood structure and metal-sheeted building 4 m
situated on bedrock of a high berm at 1160 m (3800 ft)
elevation. Its location faces the icefall on the south—
west and lies 1.6 km (1 mi) distance from it. This camp
was constructed in the spring of 1968 as a base for re-
search not only on the Vaughan Lewis Glacier but also in
the downvalley area of the lower Vaughan Lewis-Gilkey
Glacier System. In the present study it was used as a
station for working the lower glacier area, and especially
in connection with movement data taken from the berm of
Mt. Grosvenorl (Figure 2).

Observations and measurements of the internal
structures of the Vaughan Lewis Icefall were taken within
natural Openings at the glacier's surface, especially in
crevasses and stream channels (Figures 9 and 10). Measure-

ments of strike and dip were made using a Brunton compass.

Linear distance measurements were taken with a 100 ft

 

lProvisional place name suggested in honor of
Gilbert Hovey Grosvenor, National Geographic Society Presi-
dent, 1920-1950. This is in recognition of the National
Geographic Society which has provided prime support for
regional glaciological studies of which this research is
a part.

(30.5 m) surveyor‘s chain (tape),1 and a 10 ft (3.05 m)
carpenter's tape.

Movement data were obtained with a Wild -T2
theodolite using triangulating methods from a base line
the length of which was determined with an Invar Subtense
Bar. Three meter (10 ft) sections of thin-wall electrical
conduit were used as movement stakes. These proved to be
easier to place in 3 cm (1 in) holes than the previously
used 8 cm2 (2 in x 2 in) wooden stakes. Also by having a
galvanized finish they did not ablate out as fast as wooden
stakes with a lower albedo. The conduits were placed on
the glacier at pre-selected points along each movement
profile. They were drilled into the ice or firn pack to
depths of 2 m (6.5 ft) either with a 2.5 cm (1 in) SIPRE
drill or a 4 cm (1.5 in) Norwegian type hand drill. Later
in the field season when bare ice was exposed the Norwegian
"¢strem-type" drill was wholly used. Tape measurements
were also taken along the SlOpe from movement stake to
stake. After a few weeks, some of these stakes had to be
reset to their initial vertical position. This was done
by deepening the drill holes with an apprOpriate auger.
This, of course, corrected for tipping due to ablation.

Movement stakes aligned in strain-diamond patterns were

 

1Unfortunately these data were taken in feet and
fractions thereof. In research of this kind the metric
system is much preferred; however, the metric chain antici-
pated was not at C-18 at the beginning of this study, and
so for consistency the English tape continued to be used.
Conversions are made in the following pages.

10

also implanted with measurements taken from carefully
marked points on each stake. And similarly about every
seven to fourteen days these movement stakes had to be
redrilled because of ablation effects.

Various types of smaller pegs in strain-diamond
patterns were also installed in horizontal positions on
vertical crevasse walls. The data obtained from these
proved to be of little value. The reason for disappoint-
ment here relates to a number of practical problems, mostly
allied to ablation. For example, the installation of
wooden dowels into horizontally drilled holes was tried
first, then nails were driven into the ice. In each case
methods to induce freezing around the markers failed. It
was determined that any foreign material, wood or metal,
would increase ablation around the marker and thus fall
out before adequate records could be made. The best method
was found simply to drill a hole and measure from its
center. The error encountered, however, was of the same
order of magnitude as the movement expected and so the
results are so far inconclusive. With more time this
method might prove to be of value if one applies a sta—
tistical mean movement analysis.

Toward the end of the 1968 field season, a new
method was tried for the surface movement surveys. In
this a pyramid pylon (Figure 4) was constructed to hold
a movement stake more permanently in place, that is

without necessitating redrilling the bore—hole. The

ll

pylon was also invoked to hold the stake perpendicular in
spite of subsequent ablation. The technique was a modifi-
cation of the movement tripod method used in many previous
JIRP seasons. The pylon was constructed from 1.5 m (5 ft)
sections of building material, put together in such a way
as to form a pyramid with four triangular faces. The de-
vice proved to be very effective. In July, 1969 the pylon
which had been placed on survey point no. 3 in July, 1968
(wave—ogive K), was still holding its movement stake in a
vertical position. Another pylon, however, placed at
stake no. 15 in the upper apron area (Figures 4 and 5)
could not be relocated during the 1969 field season. This
one was assumed to have drOpped into a crevasse or to have
been crushed by winter snow.

It is probable that the existing pylon at survey
point no. 3 was sturdy enough to withstand very high winds1
during the winter because the complete structure, except
for the lower 15 cm (0.5 ft) was extremely abraded from
the effects of wind-driven snow. Also, this would seem to
indicate that little accumulation occurs on the crests of
wave-ogives in the autumn, winter, and spring months, i.e.,
generally mid-September to late-June. Sequential movement

records were taken on stake no. 3. Although not discussed

 

lWind velocities of 128 km/hr (80 mi/hr) were re-
corded at this site in September before the close of the
field season. Velocities at various other icefield
stations have been recorded in excess of 160 km/hr (100
mi/hr).

12

Figure 4.--Pyramid pylon marker placed at stake no.

15 in the summer of 1968. (Photo by L. R. Miller, 6
August 1968.)

Figure 5.--Stake no. 15 area late i
. n the summer of
1969. (Note absence of pyramid pylon to right of cloth
phototheodolite marker.)

. Glacier flow is f
right. (Photo by L. R. Miller, 26 August 132? left to

 

14

in detail in this report, these data will be useful for
comparison with future measurements.

To better evaluate the nature of glacier movement
and surface changes within an icefall, a unique and rather
unorthodox program involving crevasse "seeding" was inaug-
urated on 12 August 1968. In.this, sections of damaged
triangular radio tower and a total of fifty-two rectangu-
lar five-gallon gas cans (numbered with red paint) were
dropped 30 m (100 ft) apart in two large crevasses at the
tOp of the fall zone on the Vaughan Lewis névé--about
1620 m (5300 ft) elevation. For future reference a docu—
mentation of locations of these markers is given in the
1968 Camp 18 log.

The markers were positioned as a reference for
obtaining velocity data at a later time. Everything de-
pends, of course, on the cans subsequently becoming ex-
posed by ablation further down glacier. With a knowledge
of their initial position and depth--approximately 27 m
(90 ft)—-it is hOped that we can then gain a better insight
on the structure and ice flow within the icefall, as well

as information on the effects of ablation.l

 

1That these markers will eventually become exhumed
by ablation is indicated by a unique situation recently
reported by M. M. Miller (personal communication) from the
American Mount Everest Expedition of 1963. Certain items
deposited in a crevasse of the Khumbu Glacier Icefall in
March, 1963 were subsequently recovered on the surface of
the ramp-slope (apron) of the icefall more than 1.6 m
(1 mi) downvalley seven years later, i.e., in October, 1969.
It will be highly significant, however, if this does not
occur on the Vaughan Lewis Glacier a few years hence.

15

With respect to englacial structures in the ramp
area where these movement data were obtained, apparent
dips in the tectonic foliation were measured in the first
five wave-ogives found in the ice-apron area below the
icefall. These measurements were made in existing openings
and fissures in the ice surface, including longitudinal
crevasses, splaying crevasses, and meltwater runoff chan—
nels. Such features permitted observations to depths of
20 m (64 ft). The mean lower limit of actual measurement
was at about 10 m (32 ft). From the tectonic foliation,
inferences can be drawn about the structural stress and
strain distribution within the ice, as will be discussed
later.

The upper Herbert Glacier (Camp 16 arm) on the
west side of the Juneau Icefield (v. map in Figure 2 and
photo in Figure 6) was also studied in 1969 in a similar
manner, although more in a reconnaissance fashion as this
was the first field season in which that glacier was ex-
plored by members of JIRP. This activity was carried out
from Camp 16, at 1590 m (5200 ft) elevation at the upper
Mendenhall-Herbert Glacier névé. Aspects of this study too

will be discussed in the following pages.

16

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INVESTIGATION OF THE VAUGHAN LEWIS GLACIER

The Vaughan Lewis Glacier has been divided into
five glaciomorphic sectors-—the crestal névé or prime
accumulation zone, the icefall zone, the wave-ogive zone
(wave-band zone), the ogive zone, and the terminal sector

(Freers, 1966).

Observations in the Crestal Névé

 

The source névé or prime accumulation zone of the
glacier lying between 1700-1800 m (5600—5900 ft) is not of
major concern in the present study. Information concern-
ing firn stratigraphy and glaciothermal conditions has been
reported by other researchers for this and the adjoining
zone of the Taku Glacier (Miller, 1952, 1963b; Freers,
1966). In addition, surface movement data have been ob-
tained in this zone but are not discussed here as they do
not bear directly on current studies of structural fea-
tures below the icefall (Miller, g£_al., 1968).

In 1968, however, a detailed study in the lower
névé which adjoins the upper icefall zone was made empha-
sizing the sector just above the change of gradient in the

fall zone. The purpose here was to determine the type and

17

18

proportion of firn and glacier ice and to gain some in—
sight into the nature of primary structures in the glacier.
Crevasses were examined down to a depth of 27 m (90 ft),
as near to the fall zone as practical and safe. This was
done to determine if the structures observed below the
icefall and especially within the wave-ogives are of
subsequent or secondary deformational origin or of primary
stratigraphic origin. The material observed varied from
new to old surface snow to dense firn. It is of signifi-
cance that no glacial ice or foliation structures were
observed, even on exposed crevasse walls. The only pri-
mary structures found were dust layers (annual ablation
surfaces) and various diagenetic structures such as ice
strata (bands), ice glands, and ice lenses formed gener-
ally parallel to initial bedding in the firn by the re-
freezing of percolated surface water. It is emphasized
again that nearly all of these features were planar in
form, having horizontal orientations and distinguished
quite easily from the tectonic folia found in wave-Ogives

well below the icefall.

Investigation of the Icefall Zone

 

The icefall zone is defined by Freers (1966) as
that area below a point where crevasses are seen with
their downglacier walls lower than their upglacier walls,
i.e., essentially the serac and bergshrund zone. This

zone has been noted to lie within the 1675 m (5500 ft) to

19

1225 m (4000 ft) range, and as such has been the object of
intensive study by Pinchak (1968) with respect to the
periodicity and cause of diurnal avalanches.

Between 1964 and 1968, photogrammetric surveys
have been made of the Vaughan Lewis Icefall including, of
course, the acquisition of comparative photographs. These
photos also cover the wave-ogives and ogives from selected
base-lines and glacier-surface stations (Chrzanowski, 1968).
They have been obtained with a Wild P-30 phototheodolite
and are currently the base for a large-scale map of the
icefall and apron area being plotted by Dr. Adam Chrzanow-
ski and Professor Gerhard Gloss at the University of New
Brunswick. The glass plates have also been helpful in
the writer's study of annual changes in the nature of the
morphogenic features below the icefall.

At the t0p of the Vaughan Lewis Icefall there are
large curvilinear tension crevasses which degenerate down—
ward into a pronounced zone of seracs and ice pinnacles.
Within this area much avalanching occurs. During 1968
and 1969 as many as seventy-five avalanches were recorded
in a single twenty—four hour period. Although the
crevasses at the head of the icefall are wide and deep
and so could be investigated directly, because of avalanch-
ing none could be investigated within the icefall (Figure
3). A similar role for avalanches was found to character-
ize the upper Herbert Glacier (Camp 16 arm) icefall near

Camp 16 (Figure 6), proving that both of these glaciers

20

are vigorously discharging through their icefall outlets
from their source névés.

King and Lewis (1961), in reference to the Odins-
breen of the Norwegian glacier Austerdalsbreen, have sug—
gested that in such instances crevasses may extend down—
ward to the bottom layers of ice and into less disordered
ice masses which survive ablation in the icefall and thence
are moved downslope to the ice apron area below. This has
not been observed by the writer or others on the Vaughan
Lewis or the Herbert Glaciers (Freers, 1966; Kittredge,
1967). Actually what this entails is that only shallow
crevasses survive in the icefall zone and that these become
largely filled with slump material, and hence in general
obscured. Freers (1966) has cited evidence that a few do
survive into the apron and wave-ogive zone. This sub-
stantiates the writer's view that such crevasses do not
extend into ice at the bed of the glacier.

Morphogenetic and Structural Features in
the Wave—Ogive Zone

 

 

The three-dimensional wave-ogive forms in the
apron below the icefall (Figure 3) are the main focus of
attention in this study. Downglacier these surface waves
or bulges attenuate to form two—dimensional ogives
(Figure 18).

For reference purposes the wave-ogives are

lettered in a downglacier sequence (Figure 7), starting

21

 

 

 

  

MO'OII

ES bedrock
modlol naming

E "on o! wove-o3“.

E5: survey "all.
[3 Nov-no lino: VAUGHAN LEWIS GLACIER

Angus! '96.

 

Figure 7.--Sketch map of wave-ogive crests on the
Vaughan Lewis Icefall as observed in August 1968.

 

22

with J, which designates the uppermost wave-ogive studied
in 1968-69. By starting at a midpoint in the alphabet it
will be possible in the next few years of this long-term
study to extend the series by adding I, H, etc., as new
wave—ogives develOp at the base of the icefall and without
changing a numbering system each year. In Figure 7 the
present sequence downglacier is labeled as J, K, L, M, N,
O, and P. Wave-ogive P refers to the end of the dominant
surface bulges designated as wave-ogives observed in
August 1968.

The amplitude of the wave—ogives on the Vaughan
Lewis varied from 25 m (82 ft) at the base of the icefall
to 0 at a point about 2 km (1.2 mi) downglacier (Figures
8, 20, and 23). The wave length of the wave-ogives varied
from 90 to 150 m (288-480 ft). Maximum amplitude could
at no time be accurately measured without drilling a test
hole because winter snow in the intervening troughs had
not totally melted, even by the mid-September end of the
ablation season in 1968 (v. Figure 23). In 1969, the
situation was worse because new snow arrived and remained
at this level by mid-August--1969 being the year of heavi-
est summer accumulation in the whole of the past twenty-
five years of record on the Juneau Icefield.

As originally suggested by Miller (1952) and sup-
ported by Kamb (1964), the key to understanding wave-ogives

and ogives will come from studies of their internal

23

.mzmsouu new mummno m>m3 mo cowuwmom on w>aumamu mnmuma ca mo aummp ou coauwHHOM
cacoyomu mo map mcfl3onm an musmflm .>V 2 was .A .m mm>amOIm>63 mmouom mmum>muu
HmcflcsuwmsoH so meump mommusm mo cofluosuumgoomu owumEEMHmMHntl.m whamfim

 

locates:

Jufltucum.
z .032»: .— .0933.

24

structure, particularly at depth. Thus in this present
study, primary attention is given to the nature and origin
of the tectonic folia.

Tectonic foliation is a term first suggested by
Miller (Glacier bands, conference on terminology, 1953;
also v. Miller, 1952, 1955; and Taylor, 1963). As defined
in this study these are planar or foliation structures
produced by shear or compression and consisting of alter-
nate zones or seeming layers of fine and coarse-grained ice.
In some cases, grains of ice and trapped air bubbles are
elongated in the plane of the layer (Figures 9 and 10).

Rigsby (1958) and Kamb (1959b) have indicated that
both polar ice and temperate ice show a single maximum
crystal orientation (rather than the two areas of concen-
tration from the possibility known in biaxial ice crystals).
In other analyses, Gow (1964) has shown two, three, and
four maxima, but for the present analysis the probability
of a single maximum is emphasized because of the strong
unidirectional stress suggested by the geometry of the
present case.

In this analysis (v. Kamb, 1959a) the c-axis orien-
tation would be centered about the pole. Thus a single
area of concentration of the c-axis perpendicular to the
basal plane or plane of foliation is determined and plotted.
The point where the perpendicular to this plane intersects

the projection sphere is called the pole of that plane.

25

A.mmma um

nose v .umaaflz .m .q mn ouonmv

.mflaom mo QHU pamOAMHcmflm mamm>wu mcflnum no

mswmcmn mmmmfiou Scum mafia

m>wm01w>w3 Houomm
:0 ommomxm mm ma

Hmoauum> umnu muoz .M
In HHM3 mmmm>wuo mcfluuSUImmouo
How oacouomall.oa wusmflm

fli

 

x.mmma umsms4 hm

. whom one

.umaawz .m .4 an ouonmv 3 .

Eonm hHHmoflprb mcwmsmn mxm 00H muoz

.2 m>HUOIm>m3 mo Houummlm mawuuso

Immono Hmcgmno Emmnum mo Hana HMOfiuHm>
CH mwaom oacouomall.m mnsmflm

 

26

Kamb further states that the recrystallization of glacier
ice in situ during glacier flow will give a preferred
orientation of the c-axis normal to the foliation planes.
On this basis the basal planes of the individual hexagonal
crystals would be parallel to the folia. Such orientation
minimizes the chemical potential which is required for
equilibrium across the plane normal to the greatest princi—
pal axis of stress.

Such a comparative relationship has been studied
previously in this region, in fact on the adjoining Taku
Glacier where deep drill core samples were analyzed by
Bader in 1950 (Miller, 1963b). From this three-dimensional
field study of crystal fabric it was determined that from
the surface of the Taku Glacier to 42.5 m (140 ft) the
c-axes of the natural ice crystals were preferably at low
angles to the horizontal, but without any azimuth. Below
42.5 m (140 ft), the c-axes were still preferably hori-
zontal but in successively deeper samples to the base of
the bore, a progressive crowding of azimuth values was
observed towards a line of unknown orientation (presumably,
according to the above noted discussion, this would be
normal to the direction of "flow").

From this morphogenic relationship given by pre—
vious investigators of basal plane foliation (tectonic
folia) and related planar structures (Bader, 1951; Risgby,
1958; Kamb, 1959b; Miller, 1963), it was concluded that

fabric data from thin sections of Vaughan Lewis ice are

27

not mandatory for purposes of the present study. Also

it was realized that the effort required in obtaining
such information in the field time available would have
limited the areal extent of the ice structure investi-
gation. Thus, by using this seemingly relevant c-axis

to foliation relationship, an attempt is made to plot the
orientation of measured tectonic foliation. In turn some
apparent conclusions are discussed.

In Figures 11 through 16 strike and dip orien—
tations of measured folia are plotted using the lower
hemisphere of an azimuthal equal-area (Schmidt) projection
(Billings, 1954). Such a technique has been successfully
employed by Untersteiner (1955) on the Pasterze Glacier
of the Grossglocker in the Eastern Alps.

Wave-ogive J on the Vaughan Lewis Glacier (Figure
7) is referred to as a "pre-ogive" because it did not
have a well-developed trough on the upglacier side. Here
the orientation of folia varied in true dip from 34° down-
glacier to 17° upglacier; however, it must be stated that
most were very steep dips, i.e., within 20° of perpendicu—
lar. Below this, each wave—ogive was arbitrarily divided
into two sectors using the crest of the wave as the divid—
ing point. With this point of separation, structural
relations on each half of a wave could be more accurately
determined with respect to changes in the surface con-

figuration of each limb of the wave.

28

 

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.uowomamms E H.o~nlm>mz mo ummuo .NH wusmwm

.uwwomaquop E H.mmltw>m3 mo smouu .HH musmam

h m>am01m>m3 ca mwaom mo meowumusmwuo map was mxflnum mo cowusnflupmwo

.mmnmaa qcapmaaoh you umnsopnoo
mmHom vqaom no mnoapmnanoonoo pomonmm
:26. so.-. 3.... x.-. X?“ .25.

'eesmalflu

PF mnsmym

mp mnswam

 

29

 

 

.zounm an omumofiocfl cofluowufip 30Hm

.HmwomHmms E m.m¢|lm>m3 mo ummnu .wa wusmflm

.Hmaomamc3oo E v.avllm>m3 mo ummnu .MH wusmwm

.M m>am0um>m3 :H MAHOM mo mcoflumucmwuo map was mxfluum mo coflusnflnumflo

.mosmao :cavmaatm you cohsopnoo
mwaoa «mace no mnoapmupuoonoo unmouom
a?! so... x.-. x.-. so." an...

m— onsmam

 

 

30

 

.30num an topmofipsfl cofluomnflp 30am
.Hmfiomamms E a.mm|so>m3 mo ummHO .ma mnsmfim

.umeomHmcsop E N.Mh:tm>m3 mo ummuo .mH musmflm
.2 tom .2 .q mm>metm>m3

ea mflaom mo mcoflumusmfluo map was mxflnum mo cofiusnflnpmflp pmcanfiou

.mmsmao ecaumaaou you nmuzopsoo

peace peace Ho mooaumhmeonoo unmohom
:2... so... x... x.-. a?" an...

I see W a a mu

m. ohswam m_ ohsmam

 

 

31

As noted above, the folia distributions were
plotted on a Schmidt net, a projection which is true to
area. For clarity each limb of the wave-ogive was con-
sidered separately. The data from the wall exposures of
several crevasses radiating across the wave-ogives make
up the total for a single projection. Thus the strike
and dip of either exactly 100 or 150 measurements consti-
tute the point poles used to construct each Schmidt pro-
jection (again refer to the following Figures 11-16).

In many cases the bands or tectonic folia were
found to be distorted, faulted, fractured, and sometimes
bifurcated. In each instance, the most linear and distinct
section was used for measurement. Each dip reading was
taken with a possible error factor of 12°. This figure
includes both systematic error and random error, viz.,
the result of instrumentation and human limitations--and
as such, are subject to the laws of probability. By using
a percentage distribution, as shown by area on a pro—
jection, each single reading represents only 1 per cent
or less of the total information, and therefore any ex-
tremes, either unique or by personal error, do not affect
the general trend.

As can be seen in Figures 11 through 16, the
direction of folia seem to be in no way irregular or
random. There is a misleading aspect here when one looks

at the distributions in Figures 11 through 16. This is

32

because each figure is a representation of one or the
other limb of a wave; viz., those folia which are near
the centerline of a wave-ogive crest are either on one
side or the other of this centerline and thus are divided
between each half. This division lessens the total number
in each half having a dip near the perpendicular and hence
gives a misleading overall percentage near the edge of
the Schmidt projection (especially note Figure 11).

For purposes of this analysis the true dip angles
are extended artificially to depth as is done in Figure
17. Note in this figure that below the limiting depth of
observation the extension lines are dashed. The purpose
of extending these lines is to better compare the relation-
ship of adjacent dips and to see whether there is any
possible point of focus. This figure combines the foli-
ation dips as a generalized composite of data geometrically
representing information from separate but sequential
traverse lines. In this, we see that (v. Figure 12) the
tendency is for most of the folia to dip downglacier in
the trailing or upglacier sector of a wave (hereafter
referred to as the d-sector). Conversely in Figure 11
we see the dip to be generally upglacier in the leading
or downglacier sector of a wave (hereafter referred to
as the B-sector). Again it is stressed that the exten—
sion of the folia lines in Figure 17 does not imply that
these structures in nature extend in this manner at

depth. In fact, it is further noted that indeed this

33

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A 0:.H U mmmm>OHO

 

3OH®
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coauMHHOM mo map mawBOSm .e .oc wxmu
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('w) H1630

34

manner of plotting revealed no apparent relationship in
nature allied to such hypothetical focal points as the
intersections of these lines might imply.

In Figure 17 a wide range of dips is represented.
The highest percentages, however, center around 70° dip
on each limb of a wave—ogive.

The strike of these folia is essentially parallel
to the arcuate centerline of the wave-bulge--i.e., roughly
parallel to the trend of the wave-ogive crest. The values
recorded do not vary more than :10° from this centerline,
with a mean variance of :3°. The amount of error in strike
is considered to reflect human error in the method of
measurement rather than inherent differences in value.
Here the mean variance is greater because of the irregular
surface upon which measurements were taken. One factor is
the direct exposure of these surfaces to atmospheric pro-
cesses, producing much greater ablation on horizontal sur-
faces than on crevasse walls. A further consequence is
that glacier ice on these top surfaces is more bubbly,
making the strike of specific foliation zones more diffi-
cult to distinguish and trace.

In the distal or B-sectors the folia in longi—
tudinal cross-section have a tendency to be either concave
or convex downglacier; i.e., the deeper folia at the same
distance from the centerline of a crest are found to have
either larger or smaller angles to the horizontal in com-

parison with their surface dips. With all folia at a

35

rather high dip to the surface and with lesser dips on
distal B—sectors, an asymmetrical appearance is created
by the B-sector of each wave-ogive. This asymmetry is
greatest in wave-ogive J (which we see in Figure 20, with
wave-ogive J and K, left and center, reSpectively), sug-
gesting overthrusting or underthrusting effects. Indeed
on several crevasse wall profiles truncating overthrust
surfaces have been observed (Miller, 1958). According

to Billings (1954) this would be similar to the layers in
metamorphic rock1 which have yielded the most under a
given stress as in the forward B-sector of a wave—ogive,
and therefore show greater deformation.

In various places there are non-continuous lines
of folia cut by more strongly developed lines of foliation
at slightly different angles. Such foliation has been
observed by Chamberlin (1928) and also Perutz and Selig-
man (1939) along the margins of glaciers, and has been
related to differential movement and shearing. It also
suggests deep ice translation into new stress fields as
the glacier flows downvalley. From the predominance of
cross folia in the B-sector of most wave—Ogives studied,
one might conclude that in some cases high angle over-
thrusts or underthrusts have indeed developed.

There is usually well—marked foliation throughout

the entire wave-Ogive. In some areas it appears rather

 

lGlacial ice is technically a metamorphic rock.

36

jumbled, possibly because of the presence of avalanche
material which has not yet become consolidated. This dis-
orientation becomes less as one proceeds downglacier from
wave-ogive J to wave-ogive N.

As stated previously, the folia dip angle in wave-
Ogive J surface ice ranges from 34° downglacier in a-
sector to 17° upglacier in the B-sector. The total range
of similar dips in a— and B-sectors, respectively, of wave-
ogive K; are 51° and 28°, 62° and 42° in L, 70° and 38° in
M, and 67° and 71° in N. These are the extreme dip values
(i.e., angles from the horizontal) recorded in a total of
nineteen traverse cross-sections of the five largest wave—
ogives (v. Figure 7).

It is noted again that all folia in the a-sector do
not necessarily dip downglacier, nor do all folia in a
B-sector always dip upglacier. This can be seen from the
distribution of folia in Figures 11 through 16 and in part
of the profile of wave-ogive J in Figure 17 (v. anomalus
distribution of 2—8% concentrations of point poles on east
side of Figure 11 and west side of Figure 12). This again
may be the result of local deformation effects.

Also note is made of the trend toward greater
angles in the a-sectors with increasing distance down—
glacier, which in turn corresponds to changes in surface
lepe and attenuation of the wave-bulges downvalley. In
these lower valley sectors, however, the englacial folia

remain somewhat normal to the surface. A similar

37

situation, of course, is noted with respect to the mean
dip of the tectonic folia described in Figures 11 through
16.

In individual wave-ogives there are notable
changes along the crest of the wave as well. In wave—
ogive J, for example, the amplitude increases on the
order of 5-10 m (16-32 ft) as one walks from the north
end to south. This increase in amplitude is also associ—
ated with an increase of slope on the downvalley wave
surface--i.e., from 30° on the north end to 67° on the
south end of the B—sector of this wave—ogive.

Freers (1966) described nine whiter ice folds
found in the summer of 1964 above, or upglacier from, the
full-formed wave-ogives in the apron sector of the Vaughan
Lewis icefall. Most of these were extended continuously
across glacier, though some were segmented (Figure 3).
These folds have the appearance of symmetrical, double
plunging anticlines. Kittredge (1967) and the writer have
noted that these small folds seem to appear most commonly
on the surface of the larger waves. These smaller super-
imposed cleaner-ice folds diminish in frequency and size
downglacier from wave-ogive J. That is, they appear to
have their maximum expression in the upglacier sector of
the apron. Far downglacier in the main ogive zone they

disappear completely.

38

Crevasse Observations

 

Crevasses and fracture patterns on a glacier are
principally a reflection of the compressional, tensional,
and shear stresses within the upper part of the glacier.

The crevasses at the head of the Vaughan Lewis
icefall are, as have been shown, entirely of the tension
type. We have also seen that significant or deep cre—
vasses do not occur in the main icefall, but reappear in
the sector just above or at the beginning of the wave—
ogive develOpment. There are some depressions parallel-
ing the wave-ogive crests which, of course, may be cre-
vasses at depth. But essentially, as can be seen in plan
view, the most dominant crevasses are radial. This means
they are normal to the arcuate crest axes of the wave-
ogives (Figure 18). In some cases these radial fissures
are efi echelon. In others, firn in the largest radial
crevasses contain smaller fissures with efi echelon pattern
(Figure 19). It is not clear whether this smaller pattern
of fissures relates to tensional spreading of the large
crevasse walls, or to some other stress couple not yet
measured. This may even be a result of firn-pack slump
within the crevasse, combining effects of ice stress and
ablation. Such warrants further examination in a subse~
quent field season.

Such ice at the base of icefalls is subjected to
longitudinal compressional stress (Nye, 1951, 1952, 1959;

Glen, 1956). This is because of the abrupt decrease in

39

Figure 18.--Lower Vaughan Lewis Glacier showing wave-
ogives and ogives in compression zone below the icefall.
Note position of stream channel and ponded water between
wave-ogives. (Photo by L. R. Miller, August 1967.)

Figure l9.--§fi echelon fissure pattern within radial
crevasse on southern edge of Herbert Glacier. View looking
southerly Wlth main section of glacier on right and flow

direction is away from viewer. Phot '
4 August 1969.) ( o by L. R. Miller,

40

 

 

L

Figure 19

41

bedrock slope (Figures 18 and 20) and the consequent
damming effect and slowing of forward velocity. (See
effect of longitudinal stress trajectories as controlled
by even small changes in bedrock $10pe in Miller, 1958,
as measured on the adjoining Taku Glacier.) This com-
pression tends to bring pre-existing planar features or
inhomOgeneities of any kind (e.g., basal tectonic folia)
within the ice into a more vertical transverse attitude
(Allen, et_al., 1960). This mechanism has been emphasized
for the Vaughan Lewis in a new theory of wave-ogive for-
mation elucidated by Miller (1968); also Miller, et_gl.
(1968). In this regard, Untersteiner (1955) points out
further possible complexities by showing that: "corres—
ponding to the two main normal stresses we would have
altogether six directions of maximum shear stress in which
gliding could theoretically be expected." This would
imply also characters of c-axis maximum. Here again
reference can be made to the two to four maxima observed
in studies by Gow (1964), as noted earlier. Thus, the
writer is quite aware that much detailed work on this
subject is yet to be done. But again the geometry of
the Vaughan Lewis icefall suggests a single maxima.
Regardless of the foregoing, it is clear that
wave-ogives M and N have transverse crevasse patterns.
According to Nye's initial plastic flow analysis for ice
(1951), a transverse pattern can be associated with ex—

tended flow and can be further correlated from data

42

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3

 

 

 

43

obtained. Attempts have been made, however, to measure
the strain rate on the Vaughan Lewis by having four
stakes at the corners of a square and measuring the inter-
vals between successive stakes (Nye, 1959), as suggested
by Nye (1967, personal communication) and have yet to
yield much information. A similar technique for measur-
ing surface strain-rates has been applied by Wu and
Christensen (1964) on the Taku Glacier, with not entirely
satisfactory results. Many of the problems have resulted
from an inability in even solid firn to measure small
values of deformation accurately over short periods of
time. In other words, it is most difficult to avoid error
encountered by settling and ablation of surface markers.
ReCOgnizing this, in 1969 R. Little (personal communi-
cation) installed a set of 2.5 cm (1 in) pipes, 4.8 m

(16 ft) long, in squares on the Lemon Glacier at the
southwest edge of this icefield near Juneau, and attached
piano wires to a set of sensitive strain gauges placed at
the corner of each square. This technique is also cur—
rently being organized for use in a similar proqram on

the Vaughan Lewis Glacier planned for 1971.

Surface Movement, 1967-1969

 

Movement stakes were positioned on wave-ogive J
through M as indicated in Figures 7 and 20. In Figure 20
particularly we can see the upper movement stakes in

relation to the apron cross—section. Seven movement

44

stakes were also positioned on the apron below the icefall
zone. Theodolite resection of these stakes has provided
positions from which horizontal components of the move—
ment have been calculated. Longitudinal horizontal com—
ponents of daily movement have been calculated from a
Fortran computer program (Table l) which reconstructs the
triangulation surveys. The resection data were obtained
under conditions yielding a :15 seconds of arc reproduci-
bility, thus giving a maximum movement error of only
10.05 m (0.16 ft). The results are given in daily move-
ment in Tables 2, 3, and 4; with the plotted rendition of
these data shown in Figure 21.

As we look at this figure we can see that the rates
of daily horizontal movement do not agree with what Freers
(1966) found nearly a decade ago for movement on similar
stake placements on the wave—ogive zone (wave—band) in the
late summer of 1961. For the interval 8-10 August, 1961,
Freers calculated a movement for stake F-4 (compares to
the position of 1968 stake 15) of 5.20 m/day (17.1 ft/day).
For stake 15 the 1968-69 data actually give 1.06 m/day
(3.5 ft/day) as a corrected mean velocity between 8 August
and 7 September 1968. On Freers' stake F—7 a 1.68 m/day
(5.5 ft/day) movement in 1961 is shown for the stake 10
area of this 1968 study. Again one can see that these
values differ from Freers' by a factor of nearly 5. Some
of Freers' movement values have been labeled by him as

"questionable," due to the small triangulation angles

45

MH
.coauamom HouGONHHOQ OMMWMMM may BOHOQ
. . asmq :
ucme>oz .sofium>nmmno mo m60flnmm pmpomamm um>o Hammmonmonmtl.Hm muumflm
powmcmuu HmcHUsuHmGOH co ucoEm>oE oommusm amuGONHHon o

Illllltitllllillllltitxfi

I

 

us...‘ f

2: o

6'
I.
I.
I
I
1

 

 

o 1

4 a

e n

e c

1 ...

x o

. o .............. 3o. :31. a - .2: .1...“ 1

B o lllll l :2 .1113 k .. .25 2

a. 3 (I'll 32...; 3 I 6.5 ....

o .... 31a; :2 ...i a a ...... on 1

 

'2
0
Lap / s totem

46

from his base line. On this basis, the writer is willing
to assume that the 1968-1969 surveys are more representa-
tive, though of course there could be a slowing down of
the glacier's flow over this ten—year period. This latter
conclusion is deemed improbable, though, in View of the
consistency of the 1968-1969 trends as revealed in
Figure 21. More detailed future movement surveys will
help to clarify the correct interpretation.

From Havas' 1964 data as presented by Freers
(1966, Havas, 1965) surface movement of 0.35-0.42 m/day
(1.15-1.38 ft/day) is noted, although the position relation-
ship is not precisely known with respect to the stake
locations for the 1968 data. Havas' strain diamonds,
however, were in the upper wave-ogive zone--i.e., just
below the apron area--thus giving good correlation with
the computed velocities determined for 1968-1969.

Kittredge (1967) with respect to surveys made in
August, 1965 states, "The velocity of the ice in the ice—
fall itself was found to be 18 ft/day versus 2.7 ft/day
at the apron" (5.49 m/day vs. 0.82 m/day). These positions
are not located precisely either with respect to the 1968
positions, but Kittredge's values are partially corrobor—
ative.

Freers' (1966) calculated movement was determined
from two readings two days apart; Havas' (1965) calcu—
lated movement was from two readings forty-eight days

apart; Kittredge's (1967) two readings were a month apart.

47

In comparison to these somewhat sparse earlier data, the
current investigation comprised readings taken at nine
different times extending over thirteen months. The first
was on 23 July 1968; the last on 23 August 1969. Thus
again, the writer has more confidence in these compu-
tations. At least they are a more detailed contribution
to the long-term records obtained through the years by
JIRP personnel. The 1968-69 field data are listed in
complete form for future reference in Appendix A.

All of these calculated movements are not shown
in Tables 2 through 4 and three readings taken in 1969
do not appear in the total. The reason for this is that
in 1969, some stakes were missing, by being buried under
the winter snow-pack and by sliding into crevasses. Thus
the computer program used in the analysis has to take
this into account by substituting false data as fill-ins
in the program cycle.

The initial setting of these stakes was on 25 June
1968. Due to subsequent ablation effects they were reset
between the 8th and 15th of August in that year. At this
time, because of distorted holes resulting from ablation,
it was necessary to make slight changes in position of
some stakes. For example, stakes l and 2 were re-
positioned, with stake 2 being moved £0.15 m (0.5 ft)
north. (The exact change in stake 1 is not known because
the original reference hole became ablated out.) Stake 4

was moved 0.45 m (1.5 ft) NNE and stake 15 was moved 4.4 m

48

(14.6 ft) east of its original position. A field check
of the 23 July-29 July movement of stake 15 showed that
a point a short distance upglacier might be useful as an
indicator of the position of the first wave-ogive to be
developed for the summer of 1969 (wave-ogive I). The
position change of stake 15 was, therefore, to check this
possibility. (It is noted that the stake 15 position in
Figure 7 represents this later location. Also at this
time the marker was changed from a flag and pole arrange-
ment to a pyramid pylon as discussed early in this report,
and as shown in Figure 4.) Thus by adding 4.4 m (14.6 ft)
to the total movement of 3.26 m (10.33 ft) for stake 15
(v. Table 2), and calculating for a mean daily movement,
one derives a horizontal movement of 1.09 m/day (3.49
ft/day), thus putting it back within the expected range
of values obtained for stake 15 during other time inter-
vals. This, again, is shown in Tables 2 through 4.

The subsequent field check of stake 15 showed
movement to be about 1.6 m/day (5.8 ft/day). By early
September it became apparent, even from empirical obser—
vations, that this stake had been repositioned inappro-
priately and would end up after a year of movement some-
what upglacier from the crest of the develOping 1969
wave-ogive I. More accurate movement information deter-
mined by computer indicated that ice movement in the
apron area is not as great as was originally assumed.

Thus the adjustment made in stake 15 was actually in the

49

wrong direction. It should have been moved downglacier to
reposition it on the developing crest of wave-ogive I.

From data in Tables 2 through 4, it is clear that
there is a change in velocity in the vicinity of the form—
ing wave-ogive I. In corroboration, when stake 10 on the
upper apron was resurveyed in 1969, a smaller velocity was
calculated than for 1968. Whether this is a significant
difference cannot be determined.

As seen in Table 4, the velocities in the bottom
set of data include movement for the whole preceding year
and hence give an approximation of annual surface mass
transfer. Whether in fact movement in the colder months
is in agreement with those found for the warmer months of
July and August cannot from these records be inferred with
certainty. This is because the period of comparison
averages ten months (1968—1969) against two months (summer
of 1968) and hence may be subject to critical question.

It nevertheless tends to agree with an assumption by Nye
(1967, personal communication at time of his visit to this
glacier) that the velocity in such outflow glaciers may be
constant within the icefall during any given year. This
poses some question about ideas concerning seasonal changes
in velocity as discussed by Kittredge (1967). It also
enhances the current idea concerning local position changes
in velocity; i.e., a consequent damming or abrupt change

at the base of the icefall, thus giving further credence

to the concept of longitudinal stress.

50

The writer does not note a significant increase in
velocity downglacier as is stated by Kittredge (1967) con-
cerning a wave-ogive leaving the compression zone and pro-
ceeding downvalley. The foregoing interpretation can, of
course, be checked by more frequent periodic measurements
of longitudinal flow and surface deviation changes through-
out a whole year and especially surveys in the autumn,
winter, and spring. In this context it is of interest that
year around measurements on the flat intermediate elevation
névé of the Taku Glacier (Miller, 1958, 1963b) have re-
vealed a 10 per cent increase in surface velocity during
the winter months. This indication of greatest movement
in the winter months is in contraSt to what may be sug-
gested by the all too scanty data in Table 4. It may be
significant, however, that the data on the Taku Glacier
are from the broad upland zone of perennial accumulation
at about 1075 m (3500 ft) elevation in the vicinity of
Camp 10, a region of entirely different stress distri-
bution than to be expected on the Vaughan Lewis apron area.
The possibility is, however, that such seasonal variation
in "flow" in the Vaughan Lewis névé, may, still be re-
flected in and below the icefall zone, though perhaps in
an attenuated fashion. Therefore, the validity of any
interpretation suggesting uniform flow should, of course,
be checked by subsequent winter surveys. Nevertheless,
at this juncture we are reminded of the consistency in

the thirteen-month record covered by Tables 2, 3, and 4.

51

An explanation may be in the possibility that this repre-
sents an example of a dynamic self-regulating steady state
in a classical open system--a concept now well recognized
in hydrological systems (Chorley, 1962).

Though the theoretical implications of the fore-
going are tantalizing, with the insufficient data we have
available on this glacier to date one cannot really say
much more. Because of interest in this question, however,
the writer has attempted to develOp a laboratory model
(Figure 22a, b, and c) to simulate these flow patterns
using a mixture of kaolin and water along the lines first
demonstrated by Vaughan Lewis and M. M. Miller (1955).
This laboratory test was carried out in a scale-model
valley of the Vaughan Lewis Glacier itself. In this
experiment wave—bulges not unlike those on the Vaughan
Lewis apron (Figure 23) were indeed reproduced, though
on a strictly qualitative basis. Details of this effort
are given in Appendix B, and brief comments on the rele-
vance of its results are made in the final section of
this paper.

The periodicity of individual surface bulges
below the icefall on this glacier has been considered in
detail by Kittredge (1967) and others, and demonstrated
via repeated plane-table surveys to be annual in nature.
What this means is that the wave-crests of successive
wave-ogives in the apron zone move downglacier at a rate

approximately one full wave length per year. Thus,

52

.un nose + s 1A1
m3“ fin...” mmmHDQIQ>M3

101

1.mmmH noun: .umaanz .m .q an mononm1 .nn coma + a 101

.HS 0000 + OHON QEHB «av

msfi3oam HammmOH mwzmq

1n1

 

.usmfimoam>mp mo mommum msoanm> ca no
. . Doom :0
gmsmsm> man no HmUOE :HHOMMII.NN musmam new

 

53

GOHNQ OHOZ

.m

.0: mxmum

 

11mmma nmsmsm..umaflns .m .q an ouonm1
.M w>HmOIw>m3 mo 1£usom msHMOOHv 30H> maflmonmit.

pummno um nmxnmE
.mm mnsmflm

...-‘1‘“

 

54

presumably this is an annual rather than a seasonal
phenomenon, though it may attain its maximum deve10pment
at the end of the period of maximum accumulation load,
i.e., late spring. Therefore, although direct seasonal
variation may not be apparent, we may conclude that there
isia strong develOpment of at least one notable new wave-
bulge each year, and hence also a new wave-ogive annually.

Mass Transfer and Theoretical
Considerations

 

Using measurements from Kittredge (1967) and also
the current United States Geological Survey map at a scale
of l:63,360, a rough volumetric analysis was made of the
mass transfer in the Vaughan Lewis Glacier for the year
1968. The icefall is about 671 m (2200 ft) wide, the
apron 854 m (2800 ft) wide and the wave-ogive area about
732 m (2400 ft) wide. By using a conservative depth value
of 198 m (650 ft) for the wave-ogive area and a velocity
of 0.5 m/day (1.5 ft/day) one would find a volumetric

movement of 7.15 x 105 m3/day (2.34 x 106

ft3/day) through
a given wave-ogive cross-section. If one were to pass a
mass of ice through the apron cross-section of 854 m, at
the measured apron velocity of 1 m/day, one would need a
depth of 76 m (250 ft) to accommodate this same volume.
Such a theoretical depth is indicated by dotted line in
the middle left part of Figure 20.

If the depth of ice in the apron area is greater

than this theoretical depth of 76 m (250 ft), and it

55

presumably is for reasons given below, an effective sur-
face change would be necessary to accommodate such a
volume. As there is significant summer ablation in the
apron and wave-ogive zones, of course the theoretical
depth of the icefall has to be greater. Thus the note—
worthy change in velocity-~e.g., from 1.0 m/day at stake
15 to 0.5 m/day at stake 4 in a downglacier distance of
300 m--could coincide with a strong compressional force
lifting the surface upward into a wave-bulge. Such a
deformation is possibly produced by a vertical stress
release both by flow recrystallization and even discrete
movement along foliation planes, i.e., a form of intra-
foliation deformation. The accentuated pattern of foli—
ation itself may even be a result of this phase of the
deformation sequence. The upbulging represents about a
10 per cent increase in total ice thickness compared to
that beneath the adjoining wave troughs (Figure 23). The
wave-bulge would then be similar to the effects of
tangential—compression or bench-vise squeezing described
by Badgley (1965) in considering the role of oroqenic
stress in crustal tectonics.

A further consideration here is the possibility
that the up-bulging (wave-ogive surface) is not as
directly related to the presence of a bedrock threshold
(v. Figure 20) as some other observers have suggested.

A qualitative basis for this suggestion is given in

56

discussion of the writer's kaolin model experiment noted
in Appendix B.

In View of the foregoing discussion of the close
association and possible develOpment of tectonic folia
contemporaneously with the upbulging of ice where there
is an abrupt change of slope at the base of the icefall,
it should be mentioned that the development of tectonic
foliation has been considered by others to be prior to
this stage. Miller (1968a and 1968b) considers the
tectonic folia to be initiated by shear stresses at
depth some distance upglacier-—i.e., in the area of ex-
tending flow, within the icefall itself. These are pro-
duced first parallel to the bedrock surface, and then in
a complicated flow history becoming folded and deformed
and eventually to be exposed in the wave-ogives by later
ablation. The mechanism he describes relates to the com-
bined factors of rapid downvalley movement, the squeezing
of ice in the defile outlet, and to the damming effects

of compressive flow at the base of the icefall.

SUMMARY OF RESULTS AND CONCLUSIONS

Movement data corroborate the hypothesis of a
compression mechanism existing within ice of the apron
and upper wave-ogive zones. To recapitulate the results
of this study, a significant change in velocity has been
demonstrated to exist along the longitudinal transect
between the upper apron zone at the base of the icefall
and the main zone of wave-ogives. A marked change in

bedrock slope (6) translating extending (tensile) flow

 

into compressive (compression) flow, is well illustrated

 

by the shear formulae basic to the description of verti-
cal velocity profiles in glacier mechanics (i.e., ? or
rate of flow = KTn in which T = Dogsine).l Thus the
marked change in bedrock slope (0) presumed to be the
prime factor resulting in increased longitudinal com-
pression coincident with the foregoing velocity change.
This compression effect is considered to be manifest by

the described up-bulging at the surface of the glacier

 

lWhere T = shear stress in bars; D = depth of
ice in cm; p = density; g = acceleration of gravity;
and 6 = surface slope angle.

57

58

in the apron sector just below the icefall. This up-
bulging is further supported by the writer's laboratory
model tests (Figure 22) and by the cited surface con-
figuration shown in plotted cross-sections in the apron
and wave-ogive zones.

As for the periodic nature of surface bulges in
this wave-ogive system, it has been demonstrated by
previous investigators on the Juneau Icefield Research
Program (v. Kittredge, 1967) that the wave crests in
the apron zone move downglacier approximately a full
wave-length per year. Thus, although direct seasonal
variations in stress may not be significant, or at least
not apparent, there is presumably one new wave-bulge
developed each year which eventually results in a wave—
Ogive downvalley (v. left hand edge of Figure 23).

These compression effects are also consistent
with the strong develOpment and orientation of the tectonic
foliation described in earlier pages, further detailed as
follows. The dominant shear stress which Kamb (1959a)
theoretically has placed parallel to the folia and which
Miller (1968) has allied as parallel to the tectonic
folia on the margins and bed of this glacier, still may
pertain in the icefall zone. But the conclusion of this
study suggests that the dominant effect in the lobate
apron zone is not shear, but compression, the direction
of which lies normal to the folia surface (as shown in

Figures 11-16). Thus with the related c-axis of

59

individual ice crystals in this polycrystalline aggregate
explained in this way, the c-axis would lie parallel to
the longitudinal compression axes which extend radially
outward from the center of the icefall where the apron
begins and the wave-ogives originate. Thus further, the
folia develop normal to this dominant radial stress field
in this critical sector of the glacier. The existence of
this significant zone of compression is also corroborated
by the radial development and systematic distribution of
crevasses, dominated by lobate radial fissures in the ice
apron and upper wave-ogive zones.

With respect to other factors, including the
always controversial role of ablation, the results of
reconnaissance meteorological observations by the writer
and others reveal that substantial ablation does occur.
Though detailed discussion of this, however, is beyond
the quantitative SCOpe of this present report, it re-
veals that there is upwards of 20 m (64 ft) or more of
downwasting per average ablation season. Because of the
dimensional characteristics of the wave-ogives, and
further because of the results of the writer's kaolin
model experiment described in Appendix B, ablation is
considered as no more than a subordinate co-factor in
the morphogenesis of wave—ogives. In concert the various
data here discussed seem to indicate that longitudinal
compression plays the dominant role. If one is willing

to assume that the measured changes in surface velocity

60

are accompanied also by gradationally related deformation
of ice at depth in turn related to a total stress field,
then one could conceive of positive overall downvalley
compression resulting in a combined but not necessarily
contemporaneous continuous and discontinuous compressive
deformation along either pre-develOped shear foliation or
(and) currently produced radial compressive foliation,
with a strong upward component. To such a mechanism is
attributed the striking development of folia which are
suggested further to be genetically associated with the
pronounced development of wave-bulges. Together these
internal and surface phenomena constitute what has been

described as wave-ogives.

SUGGESTED ADDITIONAL INVESTIGATIONS

Evidence indicates a strong causal relation be—
tween stresses that cause faulting and crevassing near
the surface and those causing recrystallization and foli—
ation well below the ruptured zone. Thus the ice fabric
measured near the surface is indicative of fabric below
this point or certainly at depth sOme distance upglacier
from it. However, one should have some evidence that
this does exist at depth and to what extent. Consider—
ation should be given to exploration at depths greater
than 18-20 m (57—64 ft). A bore-hole with core samples
retrieved from depth and a pipe placed in such a bore-
hole, with its deformation to be subsequently measured
below the crest of a wave-ogive to a depth of 30—60 m
(96-192 ft), could yield needed information. Ideally
such information should be obtained in the glacier above
the icefall zone as well as in the apron sector below it.

Surface strain-mechanics measurements in greater
detail are also needed using the surveyed square or
strain—diamond method. Such short term data will hope—

fully be obtained on this glacier in the future from

61

62

instrumentation and measurement method currently being
developed by R. W. Little, G. Cloud, and others in re-
finement of the technique invoked by T. Wu and R.
Christensen in earlier JIRP work.

The further use of depth measuring seismic units
would also yield much further data concerning details of
bedrock configuration, eSpecially in the icefall and
apron zones.

The program concerning "seeded" markers should be
pursued with the resurveying of markers as they are found
and the evaluation of their three-dimensional movement and
the role of ablation.

Very detailed micro-ablation measurements are
needed using large arrays of stakes across much of the
ice apron and ogive zones. Such records should extend
over the melting season from April through September.

One should continue detailed periodic theodolite
surface movement stake surveys, throughout the year to
determine whether or not there are significant differences
in surface movement from summer to winter. Also time—
lapse photography would yield helpful information con—
cerning significant seasonal changes in the icefall and
possibly even direct evidence of "up—bulging" of the
wave-ogives. This kind of information can be obtained
without great expenditures of money. An expanded pro—
gram of P—30 mapping for volume comparisons also should

be invoked.

63

Added to the above, is the excellent potential
for significant results via either laser range finder, or
(and) micro-wave surveying equipment using continuous
24-hour-a-day monitoring of surface glacier flow. Allied
to this could be continuous recording, portable seismo-
grams in the ice, as well as in adjoining bedrock, to
delineate discontinuous or spasmodic flow for comparison
with the aforementioned continuous micro-wave survey data.
Such would well lead to a break-through in understanding
the true nature of continuous versus discontinuous pro-
cesses in glacier mass transfer.

Basic to the success of any such research
projects, is a small yet dedicated team of field men
deeply interested in this fascinating phase of glaciology.
This team must, however, be willing to spend a consecutive
six-month span from spring to autumn while conducting the
kind of systematic observations and measurements sug—
gested here, and of course in much more detail than the

present study has permitted.

REFERENCES

REFERENCES

Allen, C. R., W. B. Kamb, M. F. Meier and R. P. Sharp.
(1960). Structure of the Lower Blue Glacier, Wash-

ington. Jour. Geology, v. 68, no. 6, pp. 601-625.

Bader, H. (1951). Introduction to Ice Petrofabrics.
Jour. Geology, v. 59, no. 6, pp. 519-536.

 

 

Badgley, C. P. (1965). Structural and Tectonic
Principles. Harper and Row, Pub., New York.
521 p.

Billings, M. P. (1954). Structural Geology. 2nd ed.
Prentice-Hall, Inc., New Jersey. 514 p.

Chamberlin, R. T. (1928). Instrumental work on the
nature of glacier motion. Jour. Geology,

V0 36' pp. 1-300

Chorley, R. J. (1962). Geomorphology and general
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Chrzanowski, A. (1968). Glacier mapping on the Juneau
Icefield, Alaska—B.C. (abs.). Alaska Sci. Conf.,

19th, Whitehorse, Y. T.

Freers, T. F. (1966). A structural and morphogenetic
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adjacent sectors of the Juneau Icefield, Alaska,
1961-1964. Michigan State Univ. (unpublished

Master's thesis).

Glacier bands, conference on terminology. (1953).
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Glen, J. W. (1956). Measurement of the deformation of
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Jour. Glaciology, v. 2, no. 20, pp. 735-745.

64

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Gow, A. J. (1964). The inner structure of the Ross Ice
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by deep core drilling. I.A.S.H. Commission of
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Havis, T. W. (1965). Surface velocity and strain-rate
measurements on several Alaskan glaciers; 1964.
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Kamb, W. B. (1959a). Theory of preferred cyrstal orien—
tation developed by crystallization under stress.
Jour. Geology, v. 67, pp. 153—170.

 

Kamb, W. B. (1959b). Ice petrofabric observations from
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Kamb, B. (1964). Glacier geophysics. Science, v. 146,
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King, C. A. M., and W. V. Lewis. (1961). A tentative
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Lewis, W. V., and M. M. Miller. (1955). Kaolin model
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(1968). Some 1967 and 1968 measurements on
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Vaughan Lewis Glacier, Alaska. (abs.) Alaska
Sci. Conf., 19th, Whitehorse, Y. T.

 

Miller, M. M. (1952). Preliminary notes concerning
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Miller, M. M. (1955). A nomenclature for certain . .
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M. M. (1958). Phenomena associated with the
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M. M. (1963a). The Vaughan Lewis Glacier, Juneau
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M. M. (1963b). Taku Glacier evaluation study.
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M. M., T. F. Freers, T. F. Kittredge, and T. Havas.
(1968). Wave-ogive formation and associated
phenomena on the Vaughan Lewis and Gilkey Glaciers,
Juneau Icefield, Alaska-B.C. (abs.) Alaska Sci.
Conf., 19th, Whitehorse, Y. T.

F. (1951). The flow of glaciers and ice-sheets
as a problem in plasticity. Proc. Roy. Soc.,
ser. A, v. 207, no. 1091, pp. 554-572.

F. (1952). The mechanics of glacier flow.
Jour. Glaciology, v. 2, no. 12, pp. 82-93.

F. (1959). The deformation of a glacier below
an icefall. Jour. Glaciology, v. 3, no. 25,
pp. 387-408.

M. F., and G. Seligman. (1939). A crystallo—
graphic investigation of glacier structures and
the mechanism of glacier flow. Proc. Roy. Soc.,

581'. A, V. 172' pp. 335-3600

Pinchak, A. C. (1968). Avalanche activity on the Vaughan

Lewis Icefall, Alaska. Jour. Glaciology, v. 7,
no. 51, pp. 441-448.

Prather, B. W., L. Schoen, D. Classen, and H. Miller.

(1968). 1968 seismic depth measurements on
the Taku, Vaughan Lewis, and Lemon GlaCiers,
Alaska. (abs.) Alaska Sci. Conf. 19th, White-

horse, Y. T.

67

Rigsby, G. P. (1958). Fabrics of glacier and laboratory
deformed ice. Internat. Assoc. Sci. Hydrology,
pub. 47, Symposium of Chamonix, pp. 351-358.

 

Rigsby, G. P. (1960). Crystal orientation in glacier
and in experimentally deformed ice. Jour.
Glaciology, v. 3, no. 27, pp. 589—606.

 

 

Taylor, L. D. (1963). Structure and fabric on the
Burroughs Glacier, South—East Alaska. Jour.
Glaciology, v. 4, no. 36, pp. 731—752.

 

Untersteiner, N. (1955). Some observations on the
banding of glacier ice. Jour. Glaciology, v. 2,
no. 17, pp. 502—506.

Wu, T. H., and R. W. Christensen. (1964). Measurement
of surface strain-rate on Taku Glacier, Alaska.

Jour. Glaciology, v. 5, no. 39, pp. 305-313.

TABLE S

68

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70

TABLE 2.--Movement Computed for the Periods 23 July 1968--
29 July 1968 and 29 July l968--8 August 1968.

IA“

Vaughan Lewis Glacier Movement
23 July 1968--29 July 1968

57K. N0.
FT M FT/DAY M/DAY
1 4.39 1.34 0.73 0.22
2 7.47 2.28 1.25 0.33
3 8.73 2.66 1.46 0.44
4 11.43 3.148 1.90 0.58
5 11.19 3.41 1.86 0.57
6 12.72 3.88 2.12 0.65
8 17.01 5.18 2.83 0.86
9 16.71 5.09 2.79 0.85
10 17.97 5.48 3.00 0.91
15 24.77 7.55 4.13 1.26
29 July 1968--8 August 1968
STK. N0. FT M Fl/DAY MIDAY
l 6.62 2.02 0.66 0.20
2 9.66 2.94 0.97 0.29
3 10.83 3.30 1.08 0.33
4 13.39 4.08 1.34 0.41
5 15.53 4.73 1.55 0.47
6 16.42 5.00 1.64 0.50
8 21.70 6.61 2.17 0.66
9 22.08 6.73 2.21 0.67
10 25.35 7.73 2.53 0.77
15 34.56 10.54 3.46 1.05

71

TABLE 3.-—Movement Computed for the Periods 8 August 1968--
15 August 1968 and 15 August l968—-25 August 1968.

 

Vaughan Lewis Glacier Movement
8 August 1968--15 August 1968

STKo N00 FT M FT/DAY M/DAY
1 18000 5049 2057 0078
2 14000 4027 2000 0061
3 8071 2065 1024 0038
4 13035 4007 1091 0058
5 10006 3007 1044 0044
6 12071 3087 1082 0055
8 14016 4032 2002 0062
9 16047 5002 2035 0072
10 16057 5005 2037 0072
15 10068 3026 1053 0047

STK-

N00

flfl

11100000011511.110—

15 August l968--25 August 1968

FT
S086
9022

11070
12023
15001
15023
20052
20007
23040
31019

M
1079
2081
3056
3073
4058
4064
6025
6012
7013
9051

FT/DAY

0059
0092
1017
1022
1050
1052
2005
2001
2034
3012

M/DAY
0018
0028
0036
0037
0046
0046
0063
0061
0071
0095

72

TABLE 4.--Movement Computed for the Periods 25 August 1968--
7 September 1968 and 7 September l968--27 July 1969.

 

Vaughan Lewis Glacier Movement
25 August l968—-7 September 1968

STK. N0. FT M FT/DAY M/DAY
1 4.81 4.52 1.35 0.41
2 3.29 4.05 1.21 0.37
3 4.87 4.53 1.35 0.41
4 50028 6018 1084 0056
5 '0019 6015 1084 0056
6 10082 6035 1089 0058
8 5.84 7.88 2.35 0.72
9 1.71 9.67 2.88 0.88

10 6.96 8.22 2.45 0.75
15 9.51 12.04 3.59 1.09
7 September--27 July 1969

STK. 68. FT M FT’DAY g/ggY

1 417.53 127-26 1'28 0'36
2 385.74 117-57 1°19 '
1.22 0-37

3 397.09 121-03 _

. 1.50 0°46
4 487.52 148.60 , 0.42
5 451.00 137.47 1°39
6 PISSINU 0414
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Q

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UV?

APPENDICES

APPENDIX A

VAUGHAN LEWIS GLACIER COMPUTER PROGRAM
INPUT DATA, TAKEN FROM SURVEY POINTS
FFGR #5 (UPPER) AND FFGR #4
(LOWER) ON CLEAVER WEST
OF CAMP 18

73

APPENDIX A

Part 1

VAUGHAN LEWIS GLACIER CGMPUTER PRGGRAM INPUT DATA

PCVENENT STAKE
AUNBER X 10

DE50NIN03ECO0EGOMIN)SECJDEGJMINaSEC9DEGIMIN’SEC

UPPER SURVEY PQINT LQWER SURVEY PGINT

FFGR # S FFGR # 4

RIGHT LEFT RIGHT LEFT
DATA 1 (D1) 23 JULY 1968

10 3410260270161026024:1590280270339028033
20 3360230590156023032:1530370130333037002
3O 3310360300151036,30:1470490010327048042
4O 327044034:14704403201420180510322019:01
50 318:26:04:13802601701320050000312005013
60 316020011013602002401290360510309036047
80 3120210560132022022:1250030480305003033
90 3100270380130028004:1220480380302048029
100 3080300190128030040:1200290310300029034
ISO 2980590310118:59:28:1090000321289000012

02 29 JULY 1968

10 3410300110161030000:1590320420339032034
20 336029019:156028056:1530430290333043022
30 331144030015104401701470580190327058014
40 327057003:1470560480142:340390322034022
50 3180400180138040028:1320220060312022010
60 316035008:13603405901290550070309054048
R0 312042003:13204200301250280120305028012
90 310048047:13004804901230140040303:14010
100 303053026012805313001200570350300057037
150 2990370120119:37:38:1090450540289046005

D3

10
2O
30
40
50
60
80

100
150

D4

10
20
30
40
SO
60
80
90
100
150

DS

10
20
30
40
50
60
80
90
100

74

Part 2

8 AUGUST 1968

341036029016103602101590390450339039037
336037058015603705801530530450333053023
331056047015105603101480120380328012018
3280180030148017012:1420590050322058022
319:03014013900301101320480210312048032
3160590540136059042:1300230280310023016
313:140090133014025:1260050300306005030
311122014013102202901230520540303052050
309130032012903102001210410020301041058
300038039012003804601100550410290055033

15 AUGUST 1968

3410400370161040025:1590440480339044055
3360460170156046004:1540030280334003017
332006032015200602901480240030328023042
328036001014803503701430200510323020028
319018024013901802401330050360313005054
317018052013701804101309450200310045007
313034052013303403901260290220306029024
3110470050131046058:1240210330304021024
3090580020129057052:1220110540302011052
300:58028012005802001110170210291017031

25 AUGUST 1968

341046026:16104602301590510230339051021
33605500801560550120154:130450334013028
332018019015201804301480370500328038904
328054021a14805402901430420320323042028
319039015013903901801330300281313029056
317040058:13704004201310110030311010043
314005051:13400503101270050110307004041
312019003013201805201240580060304052055
3100320370130032034:122:520340302052015

150 301053052012105304401120200290292020005

D6

10
20
30

SO
60

90
100
150

D7

10
2O
3O
40
SO
60

100
150

D8

10
2O
30
4O
50
60
80
90

75

Part 3

7 SEPTEMBER 1968

341054050:161054040:160:010090340000051
3370070200157007008:1540270340334027018
3320350080152034054:1480570140328056055
329021003014902004601440140420324014034
3200070530140007034:1340030260314003019
3180120260138012:23:1310470290311046029
314043009013404300701270490000307048003
3120570450132057034:1250430180305042030
311a150460131015037:1230410460303040052
303002054012300204201130390480293038030

27 JULY 1969

344026012016402505401621580120342058051
341010004:16100902301590090400339010037
338020010015801903901550420070335042047
3320480420152:48:26:1490060540329007040
3290410270149041009:1450180590325019026
327:50001014705000101430500010323050001
326058002014605800801420120060322012050
326001006014600100911410030200321003047
32405705801440570300139045:100319045035
319951:46:12300500101330440211293940001

1 AUGUST 1969

344127036016402703701630001020343000003
3410120280161012:1901590130230339012050
338024:16015802400901551460560355047010
3320540090152154:1001490140000329013049
3290470370149027054)1450279210325027015
327055001014705500101431550010323155001
3270060110147006001:1420211300322022003
326009011:146:09a2911410130140321013010

100 32500600401450060040139:540560319055003
150 320001001012301000101330500010293050001

76

Part 4

D9 23 AUGUST 1969

10 344035022016503502001630080230343008033
20 3410250161161025017:1590270460339027045
30 3380420220158042028:1560070440336007055
40 338038003:158038:1401550270450335027047
50 3330200270153’2002901490440280329044020
60 330019037015001903501460040100326004006
80 330:19:360150:19034;146:040090326004005
9O 3260470020146047019:1410570050321057008
100 3250440540145045005:140:400270320040035
150 3230540110143054022:1380130350318013044

LIST 0F FALSE DATA “ SUBSTITUTING FUR BLANKS FGK
CDNPUTER PROGRAMING.

27 JULY 1969

D7 STAKE 6
STAKE 7
1 AUGUST 1969
D8 STAKE 6
STAKE 7

23 AUGUST 1969
D9 STAKE 7

APPENDIX B

LABORATORY SIMULATION OF VAUGHAN LEWIS ICEFALL
SHOWING MECHANICALLY DEVELOPED WAVE-BULGES
IN A VISCO-PLASTIC MATERIAL IN
A SCALE MODEL

APPENDIX B

LABORATORY SIMULATION OF VAUGHAN LEWIS ICEFALL
SHOWING MECHANICALLY DEVELOPED WAVE-BULGES
IN A VISCO-PLASTIC MATERIAL IN
A SCALE MODEL

Insofar as the movement of ice in glaciers is
partly a mechanical phenomenon, one can refer the general
mode of flow to models (Lewis and Miller, 1955). Al-
though the peculiar rheological pr0perties of ice derives
fundamentally from the unique properties of water, the
internal bodily deformation of glacial ice is not in fact
a fluid phenomenon. Rather it is an "elasto-plastic"
flowage phenomenon involving in part the reorientation
(flow recrystallization) of individual ice crystals in a
polycrystalline aggregate, and related shear displacement
within and between the ice crystals both idio-molecularly
and on discrete movement surfaces. The micrOSCOpe mani-
festation of this complex deformation process is often
an ice fabric and even distinct foliation. Microsc0pic
effects of glacial deformation are often shown by changes

in surface configuration and large scale fractures.

77

78

In an effort to demonstrate the role of the
latter in a scale model of the Vaughan Lewis Glacier,

a brief laboratory experiment was conducted. The "flow"
material employed in the model was a mixture of kaolin
(pure china clay) and water. This material was not
elasto-plastic as is glacier ice in reality, but more
truly visco-plastic as revealed by the tests.

In this laboratory simulation wave-bulges were
produced simular to those observed on the Vaughan Lewis
Icefall, Alaska. The significant aspect here is that
they were produced without any bedrock "threshold" in—
fluence. Possibly more important, they were produced
without any ablation effects to modify or exaggerate the
effects. (The possible significance of this has been
noted briefly on page 55 of the text.)

In nature wave-ogives on the Vaughan Lewis Glacier
are periodic formations, though no attempt was made to
make a time comparison with the model. In this simu-
lation gravity was the only force involved beyond slight
basal and marginal friction effects. In nature the
angle of descent of the glacier material varies between
24° and 40°, therefore in the model a mean slope angle
of 40° was used. The model was built at a scale of
1:2400 which puts the value well within the accepted
range of kaolin model glaciers given by Lewis and Miller
(1955), viz., 1:100 to l:l0,000. It reconstructed as

well as possible the icefall and valley configuration

79

from the constraints of width and slope angle. It is
important to note that no bedrock "threshold" or rise in
$10pe was built into the model downvalley from the head—
wall sector. Statistics and dimensional values used in
this laboratory model were as follows: width of original
600 m, width of model 25 cm, model ratio 2.4 x 103; length
of "fall" 44 cm; depth of kaolin 5-8 cm.

Although measurements were made of volume and
density to stay within the range of accuracy required of
a model, no attempt was made to make a quantitative
measurement of the results.

The purpose of the experiment was strictly to
condense the dynamic morphogenesis of wave-ogives into
a small unit of time, h0pefully giving more insight into
possible related and nonrelated events leading to a better
understanding of the surface bulges on the Vaughan Lewis
Glacier as seen in the field. The model proved to be a
helpful tool for demonstrating the mechanical development
of wave-bulges, without any influence from ablation or
the presence of a "classical" type bedrock threshold.

Among the features observed during flow were
transient bergschrunds, tensional crevasses, compres—
sional crevasses, splaying crevasses, and wave-bulges.
After flow ceased most of the “crevases'l resealed as a
result of the "viscous" or visco-plastic quality of the

mixture, hence, the similarity in this respect was not

80

quite like a glacier. But surface irregularities and
wave—bulges did persist, quite similar to a glacier.

Two puzzling morphogenic processes cited by
previous authors in reference to the Vaughan Lewis
Glacier were observed on the model: (1) small folds
forming in the apron area coalesced to form the crest
of a wave-bulge (simulated wave—ogive as seen in nature);
and (2) no transverse crevasses developed in the lower
icefall and apron sectors. This latter aspect may, of
course, be related to the more viscous character of the
material.

Again, however, the significance of the simulation
is the strong evidence of a sequence of surface irregu-
larities in the apron area quite similar to what is seen
in the field on the actual Vaughan Lewis and Upper Herbert
Glaciers; plus the very distinct development of wave—
bulges below the apron. The significance of the latter
morphologic unit is that these bulges appear quite
similar to those relating to the wave-ogives on the
Vaughan Lewis and Upper Herbert Glaciers, and that they
develOped without benefit of a downvalley bedrock
"threshold" (v. discussion relating to possible rele—
vance in Vaughan Lewis Glacier situation as noted in the

text, page 54).

GLOSSARY OF SELECTED GLACIOLOGICAL TERMS

GLOSSARY OF SELECTED GLACIOLOGICAL TERMS

Ablation. The wasting or surface-lowering of a glacier
by the combined processes of melting, evaporation,
and sublimation. On the Vaughan Lewis Glacier
ablation is primarily by melting.

Albedo. The percentage of incident radiation that is
reflected; hence, the degree of whiteness.

Bergschrund. The crevasse occurring at the head of a
glacier or margins of an icefield, which separates
the moving firn and ice of the glacier from the
relatively immobile firn and ice adhering to the
headwall or nunatak. This crevasse commonly
penetrates to the headwall or bed of the glacier.
It usually has a lower lip on the downvalley side.

 

Berm. Terraces which originate from the interruption of
an erosion cycle. Remnants of earlier valley floor
above present glacier surface--usually in bedrock;
i.e., a bedrock sholder.

Bubbly glacier ice. The main material of glaciers
variably containing air pockets and entrapped
water bubbles, and having a density approximating
0.88-0.90 gm/cm3.

 

Diagenesis. A process of across-stratum changes which
take place in firn due to accumulation above it,
or percolation of rain and melt-water through it;
i.e., via compaction and recrystallization, and
by refreezing of liquid water in selective zones.

 

Firn. Compacted, granular, but still pervious material
metamorphosed from old snow, and in transition to
glacier ice. Characterized by a density approxi-
mating 0.50-0.75 gm/cm3.

 

Névé. An area of old snow partly converted into ice
(i.e., area of firn). The net accumulation area
of a temperate glacier above the névé~line.

81

82

Névé-line. The elevation of the most stable position of

Ogive.
Regime.

Seracs.

the lower limit of firn or the névé. The demar—
cation line dividing the areas of net accumulation
and negative dissipation or wastage.

See wave-ogive.

The material balance (budget) of a glacier in-
volving the total accumulation and the gross
wastage in one or more budget years. The long-
term state of health of a glacier.

When two or more sets of crevasses intersect,
the surface of the glacier is torn into a broken
mass of jagged ice pinnacles known as seracs.

Tectonic foliation. Planar appearing structures produced

 

by shear or compression and consisting of alter-
nate layers of fine and coarse-grained ice. In
some cases grains of ice and trapped air bubbles
are elongated in the plane of the layer. May not
always represent discrete zones of discontinuous
shear but rather differential zonation of con-
tinuous (quasi-plastic) deformation.

Wave—band. See wave-ogive.

 

Wave-bulge. See wave-ogive.

 

Wave-ogive. The curved light and dark bands, arched or

 

convex in plan View downglacier, that in cross-
section show a pronounced surface wave with
measurable wave length and amplitude and are that
found below icefalls on some glaciers. Where the
wave character dominates, the term wave-band or
wave-bulge is applied; and where the surface wave
is not apparent and the inlaid three-dimensional
or englacial structures (usually pronounced .
tectonic foliation) dominate, the term ogive is
applied. The alternating dirty and light or clean
ice zones not yet satisfactorily explained, though
appear to relate to alternations between originally

summer versus winter snow.

m—___ _. 1. H 1. .

 

I11111111111.:‘11111111111111111