Ice movement and structural characteristics of the Cathedral Glacier system, Atlin Provincial Park,
British Columbia
by Ronald Frederick Johnson
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Earth Sciences
Montana State University
© Copyright by Ronald Frederick Johnson (1983)
Abstract:
The Cathedral Glacier is a receding double cirque glacier system located in northwestern British
Columbia. The purpose of this study was to use ice movement data and structural characteristics to
determine which cirque's flow unit is presently the most active.
Results of a horizontal ice surface movement survey show that the average rate of ice movement per
year for 1979-1981 was approximately 5.meters in the upper reaches of the upper cirque compared to
only 2.5 m in the lower cirque. There is a slight increase to 3 meters midway down-glacier in the lower
cirque flow unit.
The arcuate patterns of primary stratification on the glacier's surface delineate the two flow units.
Up-glacier dips of the primary stratification indicate that rotational slippage has occurred. However, the
presence of secondary structures indicate that englacial shear deformation has also occurred.
Crevasses are best developed in the upper reaches of the upper cirque. They are the result of extending
flow put of the accumulation zone. Crevasses are also present midway down-glacier in the lower cirque
approximately in the area where the rate of ice movement increases slightly. These crevasses indicate
extending flow over an extrapolated convex bedrock surface which exists beneath the glacier.
Longitudinal tectonic foliation was observed near the glacier margins and in the area between the two
flow units and was noted to parallel the primary stratification. This foliation results from the lateral
shear strain between the ice and cirque walls or between the different layers of primary stratification.
Transverse foliation associated with and parallel to stepped "overthrust" structures indicates
compressive shearing strain has occurred near the terminus of the glacier.
Movement data show that the rate of horizontal surface movement is approximately twice as great in
the upper cirque as it is in the lower cirque. In addition, crevasses and foliation were found to be more
numerous and better developed in the upper cirque. The conclusion drawn from these data is that the
upper cirque flow unit is presently the most active in the Cathedral Glacier. ICE MOVEMENT AND STRUCTURAL CHARACTERISTICS OF THE
CATHEDRAL GLACIER SYSTEM, ATLIN PROVINCIAL PARK,
BRITISH COLUMBIA
by
Ronald Frederick Johnson
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Master of Science
in
..
Earth Sciences
MONTANA STATE UNIVERSITY
Bozeman, Montana
April 1983
main
Lia.
N 3Yg
:T6,36,%
C,cp. 5
APPROVAL
of a thesis submitted by
Ronald Frederick Johnson
This thesis has been read by each member of the thesis committee
and has been found to be satisfactory regarding content, English usage,
format, citations, bibliographic style, and consistency, and is ready
for submission to the College of Graduate Studies
Chairperson, Graduate Committee
Approved for the Major Department
3-
Approved for the College of Graduate Studies
Date
Graduate Dean
iii
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the require­
ments for a master's degree at Montana State University, I agree that
the Library shall make it available to borrowers under rules of the
Library.
Brief quotations from this thesis are allowable without
special permission, provided that accurate acknowledgment of source
is made.
Permission for extensive quotation from or reproduction of this
thesis may be granted by my major professor, or in his/her absence,
by the Director of Libraries when, in the opinion of either, the pro­
posed use of the material is for scholarly purposes.
Any copying or
use of the material in this thesis for financial gain shall not be
allowed without my written permission.
Signature
Date
/
V
ACKNOWLEDGMENTS
Great appreciation is extended to Dr. John Montagne (Committee
Chairman) for sharing his knowledge, time and enthusiasm for the field
work and the final writing of the thesis. Dr. Maynard M. Miller for
providing valuable insight into some of the specific problems related
to the thesis, Mrs. Joan Miller for providing logistical support for
the field work, and the Foundation for Glacier and Environmental
Research for financial support.
Appreciation is also extended to Dr. Steven G. Custer and
Dr. David R. Lageson for critical review of the thesis; the entire
field crew at Camp 29, particularly John B. Price, Mike Bruzga, Gary
Mendivil, Joel Blumenthal, Scott Odden, and Chip Laymon; my wife.
Fay Shultz Johnson for putting up with my long absences and for
assistance with drafting; and Sharon Dusenberry for typing the final
draft of the thesis.
vi
TABLE OF CONTENTS
Page
1.
LIST OF TABLES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.
LIST OF FIGURES. . . . . . . .
ix
3.
ABSTRACT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xi
4.
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I
Physical Setting of the Cathedral Glacier. . . . . . . . . . . . .
Physical Characteristics of the Cathedral Glacier. . . . . . .
Previous Research. . . . . . . . . . . . .
Objectives of this Study. . . . . . . .
2
4
8
10
5.
ICE MOVEMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description of Field Procedures. . . . . . . . .
Survey Data Reduction Procedures. . . . . . . . . . . . . . . . . . .
Discussion of Ice Movement. . . . . . . . . . . . . . . . . . . . . . . .
Conclusions. . . . . . . . . . . . . .
6. STRUCTURAL CHARACTERISTICS. . . . . . .
7.
viii
12
12
14
17
20
21
Field Mapping Techniques. . . . . .
Primary Stratification... . . . . . . . . . . . . . . . . . . . . . . . . . .
Crevasses , .. . ... . . . . . . . . . . . . . . . . . . . ...............
Crevasse traces. . . . . . . . . . . . . . . . . . . . . . . . . . .
Foliation.. . . . . . . . . . . . . .
Conclusions. . . . . . . . . . .
22
24
31
38
38
42
NON-STRUCTURAL SURFACE FEATURES. . . . . . . . . . . . . . . . . . . . . .
43
Medial and Surface Debris. . . . . . . . . . . . ... ,. . . . . . . . .
Supraglacial Streams. . . . . . . . . . . . . . . .
Moulins. . . . . . . . . . .'. . . . . . . . . . . . . . . . . . . . . . . . . . .
Semipermanent N§v6 and Superimposed Ice. . . . . . . . . . . . . .
8. SUMMARY OF CONCLUSIONS. . . . . .
Relationship Between Flow Units of the Cathedral Glacier...
Zones of Compression and Tension. . . . . . . . . . . . . . . . . . . .
Nature of the Bedrock Profile Beneath the Glacier. . . . . . .
Structures Which Need Further Study. . . . . . . . . . . . . . . .
43
44
46
48
50
50
51
51
51
vii
TABLE QF C O N T E N T S - Continued
Page
9. References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.
53
APPENDICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Appendix A
Field Survey Data for 1979-1981 . . . . . . . . . . . . . . . .
Appendix B
Movement Data for 1979-1980, 1980-1981, and 1979-1981.
Appendix C
Average Rate of Movement for One Year Based on the
Rate of Movement for 1979-1981. . . . . . . . . . . . . . .
57
60
64
viii
LIST OF TABLES
Table
I.
Effects and conditions of compressive and extending flow.....
Page
34
ix
LIST OF FIGURES
Figure
Page
1 . Location map of study a rea. . . . . . . . . . . . . . . . . . . . . . . . .
3
2.
General map of the Cathedral Glacier. . . . . . . . . . . . . . . . .
5
3.
Oblique aerial photo of the Cathedral Glacier. . . . . . . . . .
6
4.
Longitudinal profiles of the glacier surface. . . . . . . . . . .
7
5.
Oblique aerial photo of the Cathedral Glacier and the
Neoglacial moraine complex. . . . . . . . . . . . . . . . . . . . . . . .
9
6. Map showing the location of base survey stations and
glacier movement stakes. . . . . . . . . . . . . . . . . . . . . . .
7.
Diagramatic representation of the glacier survey coordinate
system.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8. Map showing horizontal surface movement vectors. . . . . . . .
9.
13
16
18
Photo showing ice axe simulating the attitude of
foliation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
10.
Photo of primary stratification in the upper cirque. . . . .
25
11.
Map showing primary stratification and foliation. . . . ../...
27
12.
Diagram showing movement vectors for the glacier VeslSkautbreen, Norway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
Diagram showing calculated positions of primary strati­
fication at 10 year intervals for the glacier VeslSkautbreen, Norway.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
14.
Structure map showing crevasses and crevasse traces. . . . .
32
15.
Photo showing left stepping en echelon crevasses. . . . . . .
33
16.
Diagram showing extrapolated longitudinal bedrock profile
beneath the upper cirque. . . . . . . . . . . .
35
Diagram showing extrapolated longitudinal bedrock profile
beneath the lower cirque. . . . . . .
36
13.
17.
X
LIST OF FIGURES— Continued
Figure
18.
Page
Diagram showing the relationship between crevasse
orientations and the principle stress, ax .. . . . . . . . . . . .
37
19.
Photo of typical longitudinal tectonic foliation. . . . . . . .
39
20.
Photo of stepped "overthrust" structure. . . . . . . . . . . . . . .
41
21.
Photo of medial debris pile. . . . . . . . . . . . . . . . . . . . . . .
45
22.
Photo of supraglacial streams with sine-generated meander
forms.. . . . . . . . . . . . . . . . . . . . . . . . .
23. , Map showing non-structural surface features.. . ... . . ...
47
xi
ABSTRACT
The Cathedral Glacier is a receding double cirque glacier system
located in northwestern British Columbia. The purpose of this study
was to use ice movement data and structural characteristics to determine
which cirque's flow unit is presently the most active.
Results of a horizontal ice surface movement survey show that the .
average rate of ice movement per year for 1979-1981 was approximately
.5.meters in the upper reaches of the upper cirque compared to only
2.5 m in the lower cirque. There is a slight increase to 3 meters
midway down-glacier in the lower cirque flow unit.
The arcuate patterns of primary stratification on the glacier's
surface delineate the two flow units. Up-glacier dips of the primary
stratification indicate that rotational slippage has occurred. However,
the presence of secondary structures indicate that englacial shear
deformation has also occurred.
Crevasses are best developed in the upper reaches of the upper
cirque. They are the result of extending flow put of the accumulation
zone. Crevasses are also present midway down-glacier in the lower
cirque approximately in the area where the rate of ice movement
increases slightly. These crevasses indicate extending flow over an
extrapolated convex bedrock surface which exists beneath the glacier.
Longitudinal tectonic foliation was observed near the glacier
margins and in the area between the two flow units and was noted to
parallel the primary stratification. This foliation results from the
lateral shear strain between the ice and cirque walls or between the
different layers of primary stratification. Transverse foliation
associated with and parallel to stepped "overthrust" structures indi­
cates compressive shearing strain has occurred near the terminus of
the glacier.
Movement data show that the rate of horizontal surface movement
is approximately twice as great in the upper cirque as it is in the
lower cirque. In addition, crevasses and foliation were found to be .
more numerous and better developed in the upper cirque. The conclu­
sion drawn from these data is that the upper cirque flow unit is
presently the most active in the Cathedral Glacier.
I
I
CHAPTER I
INTRODUCTION
Research on the Cathedral Glacier began i n 1972 with the establish
ment of Camp 29, which is located on a bedrock berm near the terminus of
the glacier.
This camp serves as a research base for work conducted
under the auspices of the Foundation for Glacier and Environmental
Research at the Pacific Science Center, Seattle, Washington and its
affiliated Juneau Icefield Research Program (JIRP).
Since 1972, three major studies have been conducted that have a
direct relationship to this particular study.
The first investigation
was a field mapping project conducted by JIRP under the direction of
Dr. G. Konecny, then of the Division of Survey Engineering at the Uni­
versity of New Brunswick.
This project resulted in a topographic map
published in 1976 and used in all subsequent field work on the Cathedral
Glacier.
The second study was by V. K. Jones in 1975, resulting in a
Master's thesis in geology at Michigan State University.
best described by the title of his thesis:
His work is
"Contributions to the
Geomorphology and Neoglacial Chronology of the Cathedral Glacier
System".
The other major study is presently being completed as a
Master's thesis .by J... B. Price at the University of Arizona.
His
research concerns the 1979-80 mass balance and glacio-hydrolog.ical
characteristics of the Cathedral Glacier.
These works, which will be
2
discussed later, led to the present study involving the-movement
characteristics of the Cathedral Glacier.
Physical Setting of the Cathedral Glacier
The Cathedral Glacier is in the northwestern corner of British
Columbia at 59° 20' N latitude, 134° 5' W longitude (Figure I).
As such
it lies within the confines of the newly established Atlin Provincial
Wilderness Park.
The glacier is within the Cathedral Massif, a rugged
bedrock highland on the southwestern end of Atlin Lake.
The massif is
located just north and east of the Juneau Icefield, North America's fifth
largest continuous icefield which in turn is located in the Northern
.
v.
Boundary Range of the Alaska-British Columbia border region.
The climate of the Cathedral Massif is characterized by cold, dry
conditions and hence may be termed a periglacial environment.
These
conditions are in contrast with the maritime climate found in the
southern and western regions of the Juneau Icefield.
Because of this
contrast, the acquisition of meteorological data from the Cathedral
Glacier area is an important scientific function of Camp 29.
Meteor­
ological data obtained at Camp 29 can be compared with data from other
research stations located across the Juneau Icefield.
With these data
is is possible to obtain a better understanding of the climate of the
Juneau Icefield itself.
The data are also a key to understanding the
relationship between climate and glacial activity at both the Cathedral
Glacier site and on the main Juneau Icefield.
3
Figure I
The Northern Boundary Range and the Juneau Icefield, South­
eastern Alaska and the Atlin Lake District, British Columbia.
4
Physical Characteristics of the Cathedral Glacier
The Cathedral Glacier is a receding, north-facing cirque glacier
with a surface area of approximately 1.5 square kilometers.
lies between 1550 and 2000 meters elevation.
The glacier
The upper section of the
glacier is bifurcated into two accumulation zones (Figures 2 and 3).
Due
to an approximate 30 m elevation difference between these two accumulation
zones, they are designated as the lower and upper cirques.
These cirques
lie at the base of Cathedral Peak (2108 m) and comprise the heads of two
major flow units.
The eastern flow unit starts in the accumulation zone
of the lower cirque and the ice from here flows north past the western
flank of Mount Edward Little (1900 m) to its terminus on the eastern
side of the Camp 29 bedrock berm.
Most of the ice from the upper cirque
flows past the eastern flank of Splinter Peak (1895 m) to a proglacial
lake which has formed between the upper cirque terminus and the Camp 29
bedrock berm (Figure 2).
Some ice from the upper cirque flows east of
the bedrock berm and terminates with ice from the lower cirque.
An
aerial photograph of the Cathedral Glacier (Figure 3) provides a useful
perspective of the physical characteristics of the glacier
The topographic configuration and differences between the upper and
lower cirque, i c e surfaces can best be seen in longitudinal profiles
E-E1 and F-F1 (Figure 4).
Both cirques have relatively steep terminus
slopes that lessen upglacier in an area where the glacier widens.
A major
difference is that the ice surface slope in the lower cirque almost flat­
tens to a gently concave upward profile before rising steeply to the
5
Camp 29
Splinter Peak
1895m
wsmsi
* Edward
? Little
900m
Lower
ICiraue
1800m
SCALE
xr;:.y>-^
O
400m
XS/
1 :5 0 0 0
Approximate Contour Interval
20-25m
Cathedral Peak
2108m
Contour Lines
U
Bedrock .
Hl
Lake
fig u re 2.
---I_I
Cross Section Lines
Ice, Pirn or Snow
General map o f the Cathedral G la c ie r.
(A fte r JlRP1 1976)
Figure 3.
Oblique aerial photo of the Cathedral Glacier, view to the south.
Miller, September, 1979)
(Photo:
M. M.
LONGITUDINAL PROFILES
No Vertical Exaggeration
Elevation
1900m
Upper Cirque Ice Surface Profile
1700m
Lower Cirque Ice Surface Profile
1500m
1500m
1000m
Distance From Headwall
Figure 4.
Longitudinal profiles of the glacier surface on the upper and lower cirques.
8
headwalI , while the ice surface profile of the upper cirque maintains
a fairly even and gently convex upward profile for its entire length.
Because of the bifurcated nature of this glacier and notable physical
differences between the upper and lower cirques the Cathedral Glacier
is considered to be a double cirque glacial system.
Previous Research
An open file report of the Foundation for Glacier and Environmental
Research prepared by Guingne (1974) provides a useful reference for the
hydrologic regime of the glacier in the early 1970's, as does Miller
(1975).
From his 1973-1975 work on the moraines (Figure 5) and his
analysis of the climate of the Cathedral Glacier, Jones (1975) has
reported the following conclusions which are pertinent to the present
study:
1.
Maximum snow accumulation has alternated from one cirque to
the other, due to long-term shifts in the direction of dominant
storm winds and of associated accumulation by wind drifting.
2.
A substantial change in mass balance of this glacier system has .
taken place over a period of years, with phasing caused by dif­
fering flow distances (flow lags) from the separate accumula­
tion areas.
3.
There have been significant vertical changes in the elevation of '
the mean freezing level due to changes in mean temperature.
This in turn has periodically shifted the dominant net accumula­
tion from the lower cirque to the higher one, and vise versa.
4.
Analysis of till-boulder rock type and provenance below the
Camp 29 berm suggests that during most of the recent (post
1920's ) glacial activity the lower cirque flow unit has. been
more active.
These conclusions indicate that due to cyclic climatic changes the
mass balance has alternately changed through time between the two cirques.
Such changes in the mass balance are assumed to have affected the relative
9
Figure 5.
Oblique aerial photo of the Cathedral Glacier and the Neo­
glacial moraine complex. View is toward the southwest with
the Juneau Icefield in the background. (Photo: M. NI. Miller,
September, 1979)
10
flow activities between the two cirques.
Furthermore, during the most
recent glacial advance in this century the lower cirque flow unit was
more active than the upper cirque flow unit.
These interpretations and
assumptions raise an important question as to what the present relative
flow activity is between the two cirques.
The present study will attempt
to answer this question.
Price (Master's thesis in progress) provides insight into the present
flow activities of the two cirques with the following conclusions con­
cerning the mass balance of the Cathedral Glacier.
1.
The major accumulation for the glacier is by the deposition
of snow through wind drifting and avalanching.
2.
The mass balance of the glacier is presently negative.
3.
The mass balance of the upper cirque is less negative than the
mass balance of the lower cirque.
Thus, since the upper cirque has a less negative mass balance than
the lower cirque, the ice flow is by implication more active in the upper
cirque than in the lower cirque.
Though many other studies have been completed on the Cathedral
Glacier, the aforementioned thesis presentations of Jones and Price pro­
vide the basic background for the objectives of this study.
Objectives of this Study
The objectives of this study are:
1.
To determine the present relationship between the flow units
originating in the Tower and upper cirques.
2.
To differentiate and explain zones of compression and tension
within the glacier.
Tl
3.
To determine the. nature and estimate the topographic configura­
tion of the bedrock profile beneath the glacier.
4.
To analyze and clarify the nature, origin and significance
of discrete structures present in the glacier.
Achievement of these objectives is based on the interpretation of
field observations and data with respect to some basic glaciological
concepts.
These concepts include:
1.
The movement activity of a given flow unit within this small
glacier system is related to the present mass balance of that
flow unit.
2.
The relative movement activity between flow units can be deter­
mined by the rate of surface ice movement and the characteruand
geometry of the structures present within a given flow unit.
3.
Structure and movement data can be used to delineate the glacier
into zones of compression and tension. These data further can
be used to determine the configuration and morphology of
gross bedrock features beneath the glacier.
Procedures used for this study include:
1.
The acquisition and reduction of horizontal surface movement
data for the glacier.
2.
Mapping and description of structures within the glacier.
The remainder of this thesis will deal with the procedures used, the
data obtained during this .study and the resulting interpretations.
Ice
movement will be considered first, followed by discussions on the struc­
tural and non-structural characteristics of the glacier.
Conclusions
will be derived from application of the basic concepts stated to the
data presented.
12
CHAPTER II
ICE MOVEMENT
This chapter describes the field and office procedures used to obtain
and reduce the survey data.
The data are analyzed so that the general
horizontal surface flow characteristics of the glacier can be applied to
the understanding of the structures and relative movement characteristics
within the glacier.
Description of Field Procedures
Approximately sixty movement stakes were fixed into the surface of
the glacier during the summer of 1976.
The stakes were placed longitudi­
nally along the centers of both the upper and lower cirque flow units,
and in the area separating the two flow units (Figure 6).
These stakes
have also served as ablation stakes for use in mass balance studies.
Because of the potential ablation,.I .5 m lengths of 2.5 cm white PVC
pipes were used.
Four lengths were wired together and emplaced to a depth
of six meters by use of a thermal drill, Each section was marked with a
location number and a Roman numeral indicating which section is exposed.
As one section of the stake ablated out, it was removed from the section
which remained in the ice.
This system worked well for both the movement
and ablation studies because it allowed the stakes to be set at depth with
out the problems associated with one long section of pipe.
13
UC
LC
MP
CP
=
=
=
=
Upper Cirque
Lower Cirque
Middle Part
Central Part
Figure 6. Map showing the location of base survey stations and
glacier movement stakes for 1981.
14
In order to survey the entire surface of the glacier with as few
base survey stations as possible, two sites were selected from which
most of the movement stakes could be located.
Survey Station C was
located on the south ridge of Splinter Peak to the west of the glacier.
To the east of the glacier Survey Station A was located near the summit
of Mount Edward Little (Figure 6).
The field survey was conducted with the use of two Wild T-2 theodo­
lites using standard triangulation procedures. Because of the number of
stakes involved and the complexity of reducing vertical ice movement
data, only horizontal components of movement were recorded.
and Station C were each occupied by an instrument person.
Station A
Because the
movement stakes were white it was necessary for the rod person to use a
3 m, brown, wooden rod to facilitate the location of the movement stakes
by the instrument persons.
The rod was placed at the intersection of
the ice surface and the movement stake.
The theodolites were zeroed
on Stations A and C and horizontal angles were read for each movement
stake. . During periods of good weather, with radio communications
between members of the survey crew, it was possible to survey all the
movement stakes in one 10-12 hour period.
The field procedures
described above seemed to work quite well and are recommended for the
acquisition of future movement data for the Cathedral Glacier.
Survey Data Reduction Procedures
The field survey data allowed computation of angles between lines
connecting specific survey stations and specific movement stakes.
The
angles thus recorded were in degrees, minutes and seconds (Appendix A).
15
In order to reduce the data into a workable form the survey data were
plotted on a coordinate system.
The coordinate system for the Cathedral Glacier developed by Sidoti
(1979) was expanded for this study.
Basic trigonometry was used to
convert the angles for each movement stake to points (X9Y) on a coordinate
system.
Survey A was designated the origin (O9O) of a coordinate system
in which the Y axis extended to Survey C and the X axis extended perpen­
dicular to the Y axis.
The distance between Survey A and Survey C along
the Y axis was used as the baseline distance.
This distance is 1275 m and
was determined from the Cathedral Glacier Map (JIRP9 1976).
For each computation, with two known angles and one known side it
X
I
was possible to locate any given movement stake on the coordinate system,
as follows:
Given:
(X^,Y^) = coordinates of known point (O9O)
A 9C
- measured angles
B
= internal angle = 180-(A+C)
B
= known baseline distance
It is then possible to determine:
(Xg)Yg) = coordinates of the movement stake
C
= distance from (X^ ,Y^) to (Xg9Yg)
By employing the following calculations:
1.
C
= (sinC/sinB) B
2.
Xg
= XytCsinA
3.
Yg
= Y 1+CcosA
A diagramatic representation of this procedure is given in Figure 7.
16
Survey C
Y axis
Survey C
SCALE
400m
1:5000
Coordinates of
Known Point
Measured Angles
Known Baseline
Length
Coordinates of
Movement Stake
Internal Angle
Distance from
(X1 ,Y1 ) to
f
Vr
2
)
Figure 7.
Diagrammatic representation of the glacier survey coordinate
system.
17
All distances were measured in meters so that the coordinates are
expressed in meters.
All movement stakes to the north of the Y axis
have coordinates■(+X,+ Y ) while all other movement stakes are expressed
as (-X,+Y). The coordinate system when superimposed on a map allows the
direct location of the movement stakes for the years 1979-1981.
Horizontal surface movement was determined by using simple calcula­
tions based on the coordinate system as follows:
Given:
(X2iY2 ) = original location of movement stake
(XgiY2 ) = new position of movement stake
The distance between (XgiY2 ) and (Xg5Y2 ) can be calculated by using the
distance formula.
4.
d
The movement surveys were conducted within one week of September 1st
for each of the three years between 1979 and 1981.
lated represent the amount of movement for one year.
The distances calcu­
Appendix B lists
the calculated movement distances for 1979-1980, 1980-1981 , and 1979-1981
Appendix C lists the average movement for one year based on total move­
ment between 1979 and 1981.
Discussion of Ice Movement
A significant difference exists in the horizontal surface movement
of the two major flow units.
Appendix C and Figure 8 show that the rate
of ice movement in the upper (western) cirque is approximately twice as
great as the movement in the lower (eastern) cirque.
The increase in the rate of ice movement near the mid-section of
the lower cirque is problematic.
Ice movement from a minor flow unit
18
t f
T
SCALE
400m
1:5000
= 5 meters of movement
per year
Figure 8. Horizontal surface movement vectors. The length of each
vector represents the approximate average movement for one
year over the interval 1979-1981.
#
19
along the east margin of the glacier is converging with ice movement
from the major lower cirque flow unit.
This convergence may cause a
slight increase in the rate of longitudinal ice movement. The major
cause of the increased rate of ice movement is presumably, related to the
existence of a convex bedrock surface extending transversely beneath the
glacier.
This convex bedrock surface will be discussed in more detail in
a later part of this report.
Suffice it to say that the ice moving over
this convex surface is in extending flow (see page 33), causing an increase
in the rate of ice movement in this area.
Ice at the lower cirque terminus was observed to be less than 2 m
thick.
The existence of thin ice and the measured low values for the
rate of ice movement there indicate that the ice in this region is
practically stagnant.
Ice movement in the upper cirque is more rapid than the movement
in the lower cirque.
The greatest velocity occurs in the upper section
where movement exceeds 5 m y r ~ \
Extending flow (see page 33) coming .
out of the accumulation area is the best explanation for these high rates
of movement.
Rates of movement throughout the upper cirque decrease
-I
steadily downglacier until the velocity is less than .5 m yr .. As
is the case with the lower cirque, ice near the terminus of the upper
cirque was also found to be practically stagnant.
The rate of ice movement along the middle section of the glacier
between the two major flow units was found to be relatively constant.
Rates of movement here ranged from approximately 3 m yr~^ to 4 m yr"^ °
20
Conclusions
The horizontal surface movement data suggest that active ice is
restricted to the area upglacier from the narrow (northern) section of
the glacier (Figure 8).
Also, the lower.cirque flow unit shows a
slight increase in the rate of ice movement in ah area immediately
upglacier from where the glacier narrows.
Finally, the rate of ice
movement in the upper cirque was found to be significantly greater than
in the lower cirque.
21
CHAPTER III
STRUCTURAL CHARACTERISTICS
Analysis of the structural characteristics of the Cathedral
Glacier comprises a second major element of this study.
The significance
of this particular aspect of the research relates to the following:
1.
The location, orientation and nature of the englacial structures
provide a key to understanding the movement characteristics of
the glacier.
2.
It can be shown that the structures are related to the ice
movement characteristics discussed in Chapter II.
3.
The structures provide insight as to the nature of the bedrock
surface beneath the glacier.
The structures described are divided into two types; primary and
secondary.
Miller (1955 and 1971) has outlined these in a system used
in the nomeclature of the reports on the Juneau Icefield Research Pro­
gram.
Hambrey (1975) restates what Miller has outlined, namely that
"primary structures result from the deposition of snow or collection of
water on existing surfaces", and that "secondary structures are the result
of plastic deformation and fracture during flow."
The most important primary structure used in this study is primary ,
stratification.
Crevasses, crevasse traces and foliation are the secon­
dary structures that will be considered.
Field mapping techniques used
in plotting these structures will be discussed, followed by description
and analysis of the structures.
22
Field Mapping Techniques
A Brunton compass and tape measure were the basic field tools used
for this study.
Because movement stakes were on the glacier surface,
it was possible to locate the structures with reasonable accuracy.
The
method entailed establishing a compass bearing between a movement stake
(location known from survey data) and the structure of interest.
The
distance from the movement stake to the specific structure was then
measured.
Likewise, the trends and sizes of structures were determined
using the Brunton compass, for bearings and tape measure for distance.
Description of primary stratification and foliation often involved
the measurement of strike and dip.
Because of the lack of flat smooth
surfaces from which to take the necessary readings, the shaft, of an
ice axe was often employed to represent an extension of the attitude of
the structures being measured.
The ice axe was placed into the surface
of the glacier with a dip similar to the observed dip of the structure
(Figure 9).
The compass was placed along the shaft of the ice axe and
the angle of dip recorded.
Strikes were determined from either linear
trends of structures or from measurements perpendicular to the direc­
tion of dip. Some error is inherent in this procedure but this is con­
sidered as limited to less than five degrees.
Even with some error,
the data are sufficiently accurate to provide insight into the glacier's
structural characteristics.
23
Figure 9.
Ice axe sim ulating the a ttitu d e o f fo lia tio n . Photo was taken
in the upper cirque near the western edge o f the g la c ie r.
August, 1981)
While on the g la c ie r surface i t was often d i f f i c u l t to trace primary
s tr a tific a tio n fo r a s ig n ific a n t distance.
Such s tr a tific a tio n was best
observed from the ridges on e ith e r side o f the g la c ie r.
A technique was
devised in which radio-equipped personnel on the ridges directed radioequipped personnel on the g la c ie r to s p e c ific s ite lo c a tio n s .
Thus
personnel on the g la c ie r could walk along a s p e c ific s tr a tific a tio n
24
structure with exact guidance from the observer on the ridge.
Orange
colored wooden blocks were placed on the glacier surface so that strikes
and dips at selected sites could be measured at a later time.
This
procedure worked Well and was used for locating other structures that also
were more easily traced by viewing from some height well above the
glacier surface.
Primary Stratification
Primary stratification is a sedimentary structure resulting from the
initial deposition of snow in the accumulation area of a glacier (Miller,
1955 and Hambrey, 1975).
Structural features from this origin are well
exposed on the surface of the Cathedral Glacier in approximately2m wide
bands of coarse bubbly glacier ice alternating with dense glacier ice
or darker and less bubbly glacier ice approximately 0.2 m wide (Figure
10).
This banding is similar to the sedimentary originated banding
described by Gibson and Dyson, 1939; Clark and Lewis, 1951; Grove, 1960;
and Hambreyi 1975.
Although primary stratification is described in other
glacier studies, the studies mentioned above are more relevant to this
study as they generally deal with primary structures in other cirque
glaciers.
The banding associated with primary stratification can be explained
by considering the major changes that occur in a snowpack during a given
year.
With the onset of the accumulation season in the fall, new snow
is deposited on the glacier surface by snowfall, by wind drifting and
to some extent by snow avalanching.
The thickness of the deposited snow
is ultimately affected by the settling and densification of the snowpack.
25
Figure 10.
Primary s t r a t if ic a t io n in the upper c irq u e , view toward the
ea st. (August, 1981)
Some hard layers are formed by the a ffe c t o f wind, sun and the refree zing
o f percolated meltwater from the snow surface.
Because o f successive
snow falls in d iv id u a l storm layers do not develop to th e p o in t where they
are s ig n ific a n t observable features in the sedimentary sequence forming
prim ary s t r a t if ic a t io n .
During the a b la tio n season the new snow surface
exposed fo r long periods o f time becomes comprised o f old snow and then
26
firn.
Organic material and dust also accumulates on the snow surface.
The surface can also become saturated with meltwater.
At the end of
the ablation season the surface layer retains its identity on top of
the one year snowpack which at a density of 0.45 becomes a firn-pack
(Miller,'1971).
This cycle is completed with the beginning of the next
accumulation season.
During the transformation from new snow, to old
snow, to firn and then to glacier ice the layers develop distinct ice
characteristics.
Coarse bubbly glacier ice corresponds with the basal
accumulation layer while a dense more bubble-free ice corresponds with
the overlying ablation affected layer.
In map view the primary stratification is seen as bands with arcuate
patterns convex downglacier.
Two distinct arcuate patterns delineate the
flow units originating from the lower and upper cirques (Figure 11).
A
minor flow unit in the lower cirque can also be identified by the arcuate
nature of the primary stratification.
The arcuate patterns are caused
by retarded ice movement at the glacier margins and between flow units.
The dips of the primary stratification provides insight to the
nature of flow in the glacier, in that primary stratification dips toward
the center of each flow unit.
the margins of the flow units.
Dip angles were found to be greater near
This is consistent with the observations
of Grove (1960).
As primary stratification originates from snow deposition in the
accumulation area, the initial dip of the stratification is down-glacier
and at the angle of the existing surface.
Rotational slippage provides
the ice movement, required for the up-glacier dips observed on the
glacier.
However, rotational slippage is not the only type of ice
27
SCALE
O
Zm Om
1:5000
^ Strike and. Dip of Primary Stratification
^ Strike and Dip of Foliation
^ Vertical Foliation
'"'Trace of Representative Primary Stratification
Figure 11.
S tru ctu re map showing prim ary s t r a t if ic a t io n and f o lia t io n
observed in 1980 and 1981.
28
movement which has occurred in the Cathedral Glacier.
Other types of
ice movement will be discussed in subsequent sections of this chapter.
Rotational slippage was described by Gibson and Dyson in 1939.
They concluded that due to the weight of a wedge-shaped accumulation of
snow and firn a downward force is exerted in the accumulation zone of
the glacier, causing the sedimentary stratification to dip up-glacier
due to ice rotation.
Sharp (1954) elaborated on this type of ice move­
ment by stating that;
"Rotational slippage involves movement along curved shear
surfaces within the ice and along the bed, if of a proper
shape, with rotation about an essentially horizontal axis
above the glacier. The motive force is furnished by
unequal accumulation and distribution of snow and ice."
The results of an excellent and detailed study of the Norwegian
cirque glacier Vesl-Skautbreen (McCall, 1960) provides data to support
the -concept of rotational, slipping.
Detailed surveys of both surface
movement and tunnel deformations show a forward and downward motion in
the accumulation zone and a forward and upward heaving at the terminus
(Figures 12 and 13).
On the Cathedral Glacier, primary stratification dipping up-glacier
indicates that rotational slipping has occurred.
However, with the
glacier's present state of negative mass balance, it is difficult to
envision that the present amount of accumulation is sufficient to
provide a significant motive force for rotational slipping, thus some
of the effect in this case maybe relict.
Also, rotational slipping
assumes that little deformation occurs in the moving mass of ice; i.e.
the mass moves as a rigid body (McCall, 1960).
The secondary structures
29
Upper tunnel
Lower
tunnel
Rock Bed
meters
Figure 12.
Movement vectors fo r the g la c ie r Vesl-Skautbreen, Norway.
(McCall, 1960)
30
meters
Figure 13.
Calculated positions of primary stratification at 10 year
intervals for the glacier Vesl-Skautbreen, Norway. (McCall,
1960)
31.
discussed in the remainder of this chapter however, suggest a probable
deformation of the ice, through englacial flow deformation.
Crevasses
Due to low strain rates which correspond to. the overall low rates
of ice movement, the crevasses in the Cathedral Glacier were found to
be neither extensive nor large.
Crevasse widths ranged from approximately
I cm to I m and depths varied from a few meters to a few centimeters.
In many cases meltwater, either standing or flowing, was associated
with the crevasses.
Crevasses are concentrated in two areas of the glacier (Figure 14).
The best developed crevasse system is located in the upper reaches of the
upper cirque.
Crevasses in this area were found to be up to 200 m long
and many were concave downglacier.
50 cm.
Here the widths ranged from 10-
An interesting feature is the en echelon, left-stepping nature of
some of these crevasses (Figure 15).
Though the exact mechanism for this
phenomena is not well understood, it is assumed to be the result of dif­
fering strain rates the largest of which is favored by the thickening
ice from the margin of the glacier to the center of the flow units.
In
the lower cirque the best developed crevasse system was located approxi­
mately 800 m downglacier from the headwalI . The crevasses here consisted
of cracks only 1-2 cm wide.
Most were linear in surface expression but
many tended to be slightly concave downglacier.
Crevasse patterns on the surface of the Cathedral Glacier prove
very useful when used to interpret the types on englacial flow present.
32
SCALE
40 Om
1:5000
Crevasses
--•'''Crevasse Traces
Figure 14.
S tructure map showing crevasses and crevasse traces
observed in 1980 and 1981.
33
I
V
Figure 15.
L e ft stepping en echelon crevasses located in the upper
c irq u e , view toward the west. (August, 1981)
in the g la c ie r.
The fo llo w in g discussion is based on Nye's (1952)
c la s s ic paper on the mechanics o f g la c ie r flo w .
Nye has id e n tifie d these two types o f englacial flo w :
I ) Compres­
sive Flow, which has a lo n g itu d in a l stre ss which is compressive through­
out the depth o f the g la c ie r; and 2) Extending Flow, which is compres­
sive a t depth and te n s ile in the upper surface la y e r.
The fo llo w in g
34
table modified a fte r Nye (1952) summarizes the e ffe c ts and conditions of
these two types o f flow .
Table I .
E ffects and conditions o f compressive and extending flow .
Compressive Flow
Extending Flow ■
Effects
Upper layer in compression
No crevasses
Thrust planes
Upper layer in tension
Tranverse crevasses
(Other shear fa u lts ? )
Conditions
Ablation area
Concave bed
Accumulation area
Convex bed
At present the crevasse patterns in the Cathedral Glacier are gen­
e ra lly in d ic a tiv e o f extending flow con dition s, though as discussed la te r
there are some sections w ith compressive flow .
As previously noted, the
major crevasse system is located in the upper section o f the upper cirque.
These crevasses are related to the extending flow out o f the upper cirqu e's
accumulation area.
As has been shown in the previous chapter, th is area
is coincident w ith the highest rate o f ice movement in the g la c ie r.
The
best developed crevasses in the lower cirque are located 500-700 m downg la c ie r from the accumulation area.
This is the same area in which there
is a s lig h t increase in the rate o f ice movement, also discussed in
Chapter I I .
The probable cause fo r th is crevasse system is extending
flow over a transverse convex bedrock surface beneath the g la c ie r in its
middle section.
Figures 16 and 17 are cross sections down through the
upper cirques.
The bedrock p r o file as shown, in Figures 16 and 17 are
'
rough approximations extrapolated from the crevasse patterns and ice
,
1
‘
LONGITUDINAL PROFILE UPPER CIRQUE
Vertical Exaggeration 2x
Headwall
1900.
Glacier Surface Profile
Extrapolated Bedrock Profile
1000
Meters
Figure 16.
Extrapolated longitudinal bedrock profile beneath the upper cirque.
LONGITUDINAL PROFILE LOWER CIRQUE
Vertical Exaggeration 2x
Meters
Headwall
Glacier Surface Profile
Extrapolated Bedrock Profile
1000
Meters
Figure 17.
Extrapolated longitudinal bedrock profile beneath the lower cirque.
37
movement characteristics of the glacier.
In order to substantiate the
existence of a convex bedrock surface, further geophysical studies should
be initiated to determine the actual bedrock profile beneath the glacier.
The foregoing discussion has been based on the location of crevasses
on the glacier surface.
When the orientations of these crevasses are
considered, it is possible to gain some understanding of the stresses
present in the ice.
Nye (1952) used the angle in which the crevasses
intersect or trend toward the glacier margins to determine whether the
principle stress,(Tx, is compressive, equal to zero or tensiI (Figure 18).
The crevasses on the Cathedral Glacier intersect or trend toward the
glacier margins at angles which are greater than 45 degrees.
Thus
using N y e 1s concept, the existing crevasses are of the transverse type
and formed under conditions of tensil stress.
A
Figure 18.
B
C
The relationship between crevasse orientations and the prin­
ciple s t r e s s , (Nye, 1952). The unbroken lines show the
theoretical positions and directions of crevasses in three
possible cases. The diagrams at the top indicate the stress
acting near the margins shown uppermost in the figure. The
case for the Cathedral Glacier is shown in (c).
38
In summary the crevasse patterns in the Cathedral Glacier aid in
understanding the flow conditions in the glacier.
The location of the
crevasses indicate areas of extending flow caused by a positive snow and
ice budget in the zone of accumulation or the presence of a convex
bedrock surface midway down-glacier from that zone.
Finally, the orienta
tion of the crevasses indicate that they are of the transverse type and
formed under conditions of tensiI stress.
Crevasse Traces
'
Crevasse traces were described by Hambrey (1975) as long, thin,
steeply dipping ice layers.
It is well-known among glaciologists that
many crevasse traces represent healed crevasses and can thus be used to
indicate zones of compression.
On the Cathedral Glacier, crevasse traces
are best observed down-glacier from the major crevasse, system in the
upper cirque (Figure 14)., Other; minor crevasse traces are located in
the lower cirque, down-glacier from the extrapolated convex bedrock
surface.
These areas are thus considered to be in a concave bedrock
zone and to represent ice that is in compressive flow.
Crevasse traces
which occur in zones of extending flow may represent either the basal
remnants of crevasses that have undergone ablation or are the unopened
extensions of existing crevasses (Hambrey, 1975).
Foliation
Foliation in the Cathedral Glacier consists of thin, alternating,
discontinuous bands of bubble-rich ahd relatively bubble-free ice .
(Figure 19).
Miller (1955) refers to these as tectonic foliation bands
39
and relates them to discontinuous flow within the glacier.
the bands also show differences in grain size.
In some cases
Most of the bands ranged
from one to several centimeters in width and may trend continuously for
up to three meters.
wide and 30 cm long.
Some foliation was in the form of lenses up to 10 cm
The foliation observed was similar to foliation
described by Miller, 1955, 1971; Untersteiner, 1955; Allen and others,
1960; Hambrey, 1976; and Hooke and Huddleston, 1978.
Figure 19.
Typical longitudinal tectonic foliation developed near the
margin of the glacier in the upper cirque. (July, 1981)
40
Steeply dipping longitudinal foliation was best observed along the
margins of the glacier and in the lateral mid-section of the glacier
between the two flow units (Figure 11).
This foliation is considered
to represent lateral shear strain between the ice and cirque walls or
between the ice of the two flow units.
Transverse foliations near the terminus of the upper cirque were
in many cases associated"with stepped "overthrust" features.
Many of the
features have debris located in the down-stepped area (Figure 20).
origin of similar features has been discussed by (McCall, 1960).
The
He
concluded that "stepped features were not the result of overthrusting
but were due to differential ablation, in which the dirty ice absorbs
more heat than the adjacent cleaner ice."
By way of further explanation, the presence of foliation which, in
this case, is the result of compressive shearing strain indicates that •
some type of overthrusting has occurred in association with the stepped
"overthrust" features.
Because the ice in this area is considered
essentially stagnant, the foliation is considered primarily relict.
Though the present appearance of the stepped "overthrust" features may be
due to differential ablation, the observed foliation indicates that at
one time the compressive shearing stresses were sufficient to produce
overthrusting.
The parallelism of the tectonic foliation with primary stratifica­
tion may be a significant aspect of the Cathedral Glacier (Figure 11).
Nowhere on the surface of the glacier was foliation observed to crosscut
primary stratification.
This is probably because the primary stratifica­
tion forms zones of weakness to shear.
Hambrey (1976) observed this
41
re la tio n s h ip in the Okstaindan g la c ie rs o f Norway.
He concludes th a t
d iffe r e n tia l movement may cause shearing between d iffe r e n t layers and
the subsequent r e c r y s ta lliz a tio n o f the ice produces the f o lia t io n .
The
evidence seen on the Cathedral G lacie r supports th is conclusion.
Figure 20.
Stepped "o v e rth ru s t" s tru c tu re o ve rlying dark debris la ye r
near the terminus o f the upper cirq u e . The re la te d "over­
th ru s t" fea ture is dipping toward the l e f t o f the photo,
view toward the west. (August, 1981)
42
Conclusion
The up-glacier dips of primary stratification indicate that rota­
tional slipping is a factor in ice movement for the Cathedral Glacier.
However, the existence of crevasses, crevasse traces and tectonic folia­
tion indicates that discontinuous englacial shear deformation also occurs
within the glacier. . Therefore, the nature of ice movement within this
glacier is considered to combine rotational slippage and englacial shear
deformation.
Extending and compressive flow are two well-known types of englacial
ice deformation.
Extending flow generally occurs in the accumulation
area and where a convex bedrock surface exists beneath the glacier.
The location of open crevasses together with the higher rates of ice
movement readily delineate the areas of extending flow on the Cathedral
Glacier.
Crevasse traces and a slower rate of flow in a very general
way delineate this glacier's areas of compressive flow.
Longitudinal tectonic foliation results from the lateral shear
strain between the ice and cirque walls or between the ice of the two
flow units.
Transverse foliation associated with stepped "overthrust"
features indicate compressive shearing strain near the terminus of the
glacier.
Finally, the parallelism of the secondary tectonic foliation
and primary stratification is noted.
The described foliation is caused
by the flow shearing between the different layers of primary stratificati o n .
43
CHAPTER IV
NON-STRUCTURAL SURFACE FEATURES
Non-structural surface features are those features on the surface of
the glacier that are not directly related to the ice movement of the
glacier.
Non-structural surface features were mapped because they com­
prise the majority of surface features on the glacier and they can be
used as direct aids in discerning some of the flow characteristics of
the glacier.
Such features include, medial and surface debris, supra-
glacial streams, moulins, semipermanent n§v§ lines and superimposed ice.
These non-structural features are discussed in this chapter.
Medial and Surface Debris
The surface of the glacier is littered with debris derived by mass
wastage off of the headwalls and surrounding sidewalls of the two
adjacent cirques.
The. debris originates in two rock types exposed on
the cirque headwalI . Metabasaltic rock comprises the highest part of .
the headwal!. This rock is intruded by granodiorite, as indicated by
the contact between the two rock types seen on the headwalI of the upper
cirque (Figure. 3).
The flanks of Mount Edward Little and Splinter Peak
consist primarily of the granodiorite.
Due to the bedrock contact on
the cirque headwalI, granodiorite debris is located on the western part
of the glacier while metabasaltic rocks comprise most of the debris on
the eastern side of the glacier.
The size of the debris ranges from
44
several centimeters to several meters in longest dimension.
A meta-
basaltic block 7.5 m x 3.5 m found near the center of the glacier was
the largest debris block observed.
Though rock debris is scattered over most of the glacier surface,
in a few areas the debris is concentrated in linear piles.
The most
noticeable pile is located in the center of the glacier and is referred
to as the medial debris pile (Figure 21).
This pile consists of meta-
basaltic rock and trends for 120 m longitudinally in a zone which sepa­
rates the upper and lower flow units.
Another major linear debris pile
occurs near the west margin of the glacier and consists of granodiorite
blocks.
These debris piles are the result of periodic rockfalls from the
cirque headwall onto the glacier surface.
Subsequent ice movement
carries the debris down-glacier and also accentuates the linear shapes
of the piles.
Other scattered rock debris on the glacier surface is a
consequence of rockfalls from the over-steepened cirque sidewalls and
headwalls .
Supraglacial Streams
Some of the most striking features on the surface of this glacier
are the sine-generated meanders of supraglacial streams.
The best
developed streams are located between the mid-section of the glacier and
the terminus of both upper and lower cirques (Figure 22).
Most of the
streams are several hundred meters in length with depths ranging from
0.5 m to 3 m.
These streams act as channels for water derived from the
melting of the snow, fi.rn and ice on the upper reaches of the glacier.
45
Figure 21.
Medial debris p ile located near the middle of the g la c ie r.
View is toward the northwest, taken from the east margin of
the g la c ie r in August, 1981.
Most o f the streams have minor trib u ta rie s flow ing in to them, thus form­
ing a somewhat d e n d ritic drainage pattern.
Sugden and John (1979) have noted th a t "the sine-generated nature
o f the meanders can be expected in a uniform medium lik e ic e ."
However,
in some cases i t appears th a t ir r e g u la r itie s in the meander pattern may
be caused by primary s tr a tific a tio n or other impending s tru c tu re .
ideas are noted by M ille r (1982, personal communication).
These
46
Figure 22.
Supraglacial streams w ith sine-generated meander forms
located near the terminus o f the upper c irq u e . View toward
the south, taken in August, 1981.
Moul ins
Moulins are r e s tric te d to the r e la tiv e ly f l a t area o f the g la c ie r
surface in the lower cirque (Figure 23).
In the summer o f 1981 three
major moulins were located in th is area.
The la rg e s t had surface dimen­
sions o f 4.2 m x 3.0 m, w hile the oth er two had dimensions on the order
47
•* Moulins
'v Debris Piles
Superimposed Ice Zo n e , 1981
Figure 23.
Map showing non-structural surface features.
48
of I m x 2 m with undetermined depth.
In 1980, however, one of the
tnoulins was descended to a depth of 50 m, which is well below the deep­
est crevasse level.
At that depth the moulin interconnected with a
system of englacial streams, indicating that the ice in this area is
at least 50 m thick.
The moulins were fed by a relatively straight
and narrow supraglacial stream, about 150 m in length and nourished
by the upper glacier n6v6 zone.
Semipermanent NevS and Superimposed Ice
The semipermanent n6v6-line, 1981, was located in the upper reaches
of the glacier.
Superimposed ice was positioned a few feet just down-
glacier from the semipermanent n6v6 (Figure 23) and in places merged
with it.
The width of the superimposed ice ranged from one to several
meters.
Superimposed ice results from the refreezing of meltwater from
the snow and firn in the accumulation area.
The meltwater is refrozen
when it comes in contact with the cold glacier ice at this location.
The presence of cold ice is a thermophysical characteristic of the
Cathedral Glacier.
Jones (1975) states that "englacial temperature
measurements to a depth of 18 m in 1972 indicated that this glacier
is thermophysicalIy sub-polar in its upper headwall portion; i.e.
above 1820 m.
(0° C)."
Below the 1730 m elevation, it is essentially temperate
A sub-polar glacier is characterized by englacial temperatures
of -2° C to -10° C with a surface layer of O0 C due to seasonal warming
(Miller, 1976).
Therefore when surface flowing meltwater comes in
contact with ice that is below O0 C it freezes and forms superimposed
ice.
This means that the annual semipermanent equilibrium line is
I
49
represented by the lower edge of the superimposed ice as opposed
to the semipermanent n6v6 line represented by the lower margin of the
retained firn-pack.
50
CHAPTER V
SUMMARY OF CONCLUSIONS
This study was based on four objectives:
1.
To determine the present relationship between the flow units
originating from the lower and upper cirques accumulation
zones.
2.
To delineate the glacier into zones and sectors of compression
and tension.
3.
To determine the approximate morphology of the bedrock profile
beneath the glacier.
4.
To comment on any significant structures, including some which
require further research.
This study will conclude with comments on each of these objectives.
Relationship Between Flow Units of the Cathedral Glacier
Jones' work (1975) as outlined in Chapter I , indicates that the.
mass balance was alternately changed through time between the two cirques.
Mass balance studies by Price (in progress) lead to the conclusion that
the mass balance for 1979-1980 was less negative in the upper cirque
than in the lower c i rque.• Movement data from this study show that the
rate of horizontal surface movement is approximately twice as great in
the upper cirque as compared to the lower cirque.
In addition, crevasses
and foliation in 1980 and 1981 were found to be better developed in the
upper cirque.
The conclusion drawn from these data is that the upper
cirque flow unit is presently the most active in the Cathedral Glacier.
51
Zones o f Compression and Tension
Analysis o f crevasse patterns and o rie n ta tio n s in d ica te th a t the
crevasses are o f the transverse type mostly formed under conditions of
te n s ile stre ss.
Crevasses are located near the accumulation zone and
approximately midway down-glacier from the headwall.. Therefore these
areas are considered tensional zones.
Zones o f compression e x is t near
the terminus o f the g la c ie r and in the area between areas containing
crevasses.
Structures which are in d ic a tiv e o f compressive zones are
crevasse tra ces, "o ve rth ru st" features and transverse fo lia tio n .
Nature o f the Bedrock P ro file Beneath the G lacier
The existence o f s ig n ific a n t crevasses and a s lig h t increase in the
rate o f ice movement midway down-glacier in the lower cirque fu rth e r
conote extending flo w .
Lacking s u ffic ie n t accumulation evidence, the
most lik e ly cause fo r extending flow in th is sector is a convex bedrock
surface which trends transversely beneath the g la c ie r.
Figures 16 and
17 show the extrapolated p r o file o f the bedrock surface beneath the
upper and lower cirques.
There is need fo r fu rth e r studies using
geophysical techniques to determine the exact depth o f the ice and the
morphological configuration in the bedrock p r o file .
Structures Which Need Further Study
This section is intended to id e n tify those structures which need
fu rth e r detailed study.
These features include a zone o f le ft-s te p p in g .
en echelon crevasses located in the upper cirque and a set o f "over­
th ru s t" features near the g la c ie r terminus.
Also deserving fu rth e r
52
study is the relationship between tectonic foliation and primary
stratification structures throughout the glacier system.
More detailed
studies of these structures and their future modification will aid in
the understanding of the regimen and movement of the Cathedral Glacier.
It is hoped that the information in this thesis will serve as a
useful reference and base for further studies of this unique and inter­
esting glacier system.
-v T
53
REFERENCES CITED
54
REFERENCES CITED
A lle n , C.R., and-others, 1960, Structure o f the lower Blue G lacier,
Washington: Journal o f Geology, y. 68, p. 601-625.
C lark, J.M ., and Lewis, W.V., 1951, Rotational movement in cirque and
v a lle y g la c ie rs : Journal of Geology, v. 59, p. 546-566.
Gibson, G-R- and Dyson, J .L ., 1939, Grinnel G lacier, Glacier National
Park, Montana: Geological Society o f America B u lle tin , v. 50,
p. 681-696.
Grove, J.M ., 1960, The bands and layers o f Vesl-Skautbreen, iji Lewis,
V.R ., e d ., Norwegian cirque g la c ie rs : Royal Geographic" Research
Service, no. 4 ,.p . 39-62.
Guigne, J .Y ., 1974, Hydrological observations on the Lemon and Cathedral
G laciers: Research Report, Juneau Ic e fie ld Research Program,
Foundation fo r G lacier and Environmental Research.
Hambrey, M .J., 1975, The o rig in of fo lia tio n in g la c ie rs , evidence
from some Norwegian examples: Journal o f Glaciology, v. 14,
p. 181-185.
Hambrey, M .J., 1976, S tructure o f the g la c ie r Charles Rabots Bre,
Norway: Geological Society of America B u lle tin , v. 87, p. 16291637.
Hooke, R .L., and Hudleston, P .J ., 1978, O rigin o f fo lia tio n in g la cie rs:
Journal o f G laciology, v. 20, no. 83, p. 285-299.
JIRP, 1976, Topographic map o f the Cathedral G lacier: Juneau Ic e fie ld
Research Program, Foundation fo r G lacier and Environmental Research
Jones, V .K ., 1975, C ontributions to the geomorphology and Neoglacial
chronology o f the Cathedral G lacier System, A tlin Wilderness
Park, B ritis h Columbia: unpublished M.S. th e s is , Michigan.State
U n iv e rs ity , Lansing, Michigan, 183 p. ,
M ille r , M.M., 1955, A nomenclature fo r c e rta in englacial structures:
Acta Geographica, v. 14, p. 291-299.
M ille r , M.M., 1971, Glaciers and glacio logy: McGraw-Hill Encyclopedia
o f Science and Technology, v. 6, p. 218-229.
M ille r , M.M., 1975, A mountain, and g la c ie r te rra in study and related
in ve stig a tio n s in the Juneau Ic e fie ld region, Alaska-Canada:
Final Report, U.S. Army Research O ffic e , Durham.
55
Miller, M.M., 1955, Thermo-physical characteristics of glaciers-toward
a rational classification: Journal of Glaciology, v. 16, no. 74,
p. 297-300.
Nye, J.F., 1952, The mechanics of glacier flow:
v. 2, p. 82-93.
Journal of Glaciology,
Sidoti, P., 1979, The 1979 Cathedral Glacier survey: Research Report,
Juneau Icefield Research Program, Foundation for Glacier and
Environmental Research.
Untersteiner, N., 1955, Some observations on the banding of glacier
ice: Journal of Glaciology, v. 2, p. 502-506.
APPENDICES
57
APPENDIX A
FIELD SURVEY DATA FOR 1979-1981
/
I
58
APPENDIX A
Field Data for 1979, 1980, and 1981. Data is in degrees, minutes and
seconds. Nineteen seventy-nine data obtained by Sidoti, Bruzga and
Harding. Nineteen eighty data obtained by Johnson, Rassmusen
and Bruzga. Nineteen eighty-one data obtained by Johnson, Beck and
Klienman.
STAKE
NO.
1979
Survey C Survey A
UCOOO
UC003
UC004
UC005
UC006
UC007
UC008
UC009
UCOlO
UCOll
UCOl 3
UCOl 4
UC
MP006
MP007
MP008
MP009
MPOlO
MPOll
MPOl 2
MPOl 2
MPOl 4
LCOOl
LC002
22
04
15
25
30
33
06
26
00
05
38
21
19
03
10
16
17
18
29
20
28
46
11
58
45 13 53
24 43 32
62
69
74
81
84
50
19
28
43
08
01
24
44
53
58
30
32
35
39
41
21
55
17
15
26
23
02
12
15
27
07
16
23
30
37
42
47
51
54
24
20
31
03
51
56
09
34
17
21
44
31
41
28
12
20
26
08
33
18
25
40
27
25
07
16
23
30
37
42
46
50
53
43
34
37
01
45
52
02
05
23
15
15
28
16
43
06
46
30
49
46
21
29
23
19
36
1980
Survey C Survey A
22
04
14
25
35
44
54
62
69
74
81
84
29
16
49
05
05
51
06
30
04
17
39
07
32
20
14
02
24
04
21
25
27
08
24
20
19
03
10
16
21
25
27
30
32
35
39
41
16
06
12
18
11
33
40
12
43
08
06
17
56
02
11
44
36
01
03
35
58
32
22
39
07 16 10 07 19 09
15 49 30 15 47 00
23 37 54 23 32 17
36
42
47
51
54
24
20
57
24
08
12
38
32
42
23
01
13
50
03
23
36
36
41
46
49
53
43
34
52
55
11
53
07
29
18
30
59
55
08
46
04
20
1981
Survey C Survey A
04
14
24
34
44
53
62
68
74
81
84
01
33
45
44
30
46
12
50
07
36
07
03
06
56
57
10
04
00
08
22
14
11
02
09
16
21
24
27
30
32
35
38
41
53
60
07
01
23
31
04
35
00
57
08
55
18
24
27
34
58
15
19
37
29
27
07
15
23
30
36
42
46
51
54
23
20
01
36
24
30
46
14
58
05
32
33
43
25
13
48
42
51
19
54
49
20
00
38
07
15
23
30
36
41
46
49
53
43
34
02 08
31 06
16 18
26 46
41 03
44 42
02 45
45 41
00 00
30 06
20 11
59
STAKE
NO.
1979
Survey C Survey A
1980
Survey C Survey A
1981
Survey C Survey A
LC005
LC006
LC007
LC008
LC009
LCOlO
LCOll
LCOl 2
LCOl 3
02
04
11
17
21
24
28
30
33
40
30
09
00
30
55
20
53
29
30
46
20
21
16
28
27
33
34
03
06
17
28
39
48
58
66
71
50
49
56
55
43
55
37
02
54
38
38
14
22
22
15
16
56
41
02
04
10
16
21
24
28
30
33
03 01 08
04 08 04
001
002
003
004
005
006
007
010
on
012
014
016
03
03
06
43
55
59
27
31
54
57
08
47
45
04
49
57
45
22
05
07
17
17
19
25
45
56
20
59
54
05
15
34
44
18
50
31
03 15 53 05 25 36
03 24 11 07 42 Ol
06
90
22
16
39
30
29
05
57
17
10
36
03
52
58
12
38
51
56
27
OO
36
44
41
24
47
43
12
50
14
59
70
06
90
22
50
19
58
49
20
47
14
48
25
24
20
20
29
08
57
21
45
07
47
16
46
40
15
58
32
12
10
27
04
06
17
28
39
48
58
65
71
24
28
11
38
51
05
31
39
35
26
39
25
52
48
56
52
42
28
48
01
36
01
38
28
49
03
58
01
10
05
03
42
14
04 20 07
06 13 07
16
21
24
28
30
33
38
11
39
09
44
20
25 28 15 58
27 39 09 15
44 48 26 07
14 58 16 11
24 65 43 56
46 71 39 23
03
03
06
43
54
59
70
06
90
22
16
38
04
18
43
06
23
04
04
10
29
11
56
43
46
11
12
47
40
22
09
76
42
44
21
24
05
07
16
17
19
24
28
11
48
51
56
27
06
27
33
41
37
47
43
21
21
53
34
04
17
09
02
05
51
48
28
35
10
23
08
29
60
APPENDIX B
MOVEMENT DATA FOR 1979-1980, 1980-1981, and 1979-1981
APPENDIX B
Reduced Data for 1979, 1980, and 1981.
STAKE
NO.
UCOOO
UC003
UC004
UC005
UC006
UC007
UC008
UC009
UCOlO
UCOll
UCOl 3
UCOl 4
1979
X
Y
241.9
42.7
140.0
231.4
691.1
738.2
756.5
788.7
403.0
875.3
574.6
663.3
754.1
931.3
1032.3
980.3
1024.6
1065.6
1139.7
1169.2
Coordinates are in meters.
COORDINATES
1980
X
Y
241.8
40.0
136.6
229.6
318.6
484.6
569.7
657.7
749.1
926.0
1027.0
691.1
738.6
758.8
784.5
821.6
924.3
978.5
1023.5
1064.2
1139.2
1169.3
1981
X
37.5
133.9
226.6
315.4
395.6
480.9
565.6
653.3
744.8
921.0
1021.3
Movement is in m yr
79-80
MOVEMENT
80-81 79-80
Y
740.9
759.1
783.8
820.5
872.5
922.6
976.8
1022.0
1063.2
1139.0
1169.8
.1
2.7
4.1
4.6
3.7
2.7
3.0
3.4
5.9
6.6
6.9
7,9
5.2
5.7
5.2
5.3
5.3
4.1
4.4
4.6
4.4
5.0
5.1
9.7
10.3
9.6
10.3
10.4
STAKE
COORDINATES
MOVEMENT
1981
1980
1979
NO.
X
Y
X
Y
X
Y
MP006
MP007
MP008
MP009
MPOlO
MPOlO
MPOl 2
MPOl 3
MPOl 4
84.8
183.2
281.3
381.6
482.2
580.8
679.7
633.0
638.2
638.9
638.3
638.8
642.9
647.5
81.5
180.4
278.3
635.3
638.4
638.9
877.2
654.9
478.9
577.4
675.6
774.5
873.4
638.4
642.8
648.0
652.6
655.1
78.5
177.6
275.0
375.2
475.7
573.8
672.0
771.2
869.8
637.0
639.3
639.7
638.3
638.6
643.0
647.9
652:6
655.4
LCOOl
LC002
LC005
LC006
LC007
LC008
LC009
LCOlO
LCOll
LCOl 2
LCOl 3
392.7
309.9
35.1
60.6
156.2
251.0
340.8
421.7
517.5
602.7
693.7
414.2
454.6
523.1
506.6
482.6
247.9
410.1
367.6
315.6
267.7
226.6
392.9
310.2
37.4
58.0
153.7
247.9
337.8
418.7
514.9
600.1
691.4
414.3
454.6
523.7
507.2
582.9
454.8
410.6
368.3
316.5
268.7
227.3
310.5
39.7
55.4
454.5
523.1
508.5
334.8
416.0
512.7
579.9
688.7
411.2
368.9
317.0
296.6
228.4
79-80
80-81
79-81
3.9
2.8
3.0
3.4
2.9
3.4
3.3
3.4
4.1
3.2
3.6
3.6
3.3
3.6
7.4
5.7
6.4
6.4
6.5
7.0
7.7
3.8
.22
.3
2.3
2.6
2.5
3.1
3.0
3.1
2.8
2.8
2.4
7.4
.32
2.4
2.9
.61
4.6
5.5
3.1
2.8
2.3
2.4
2.9
6.1
5.8
5.0
5.2
5.3
STAKE
NO.
X
Y
48.2
54.4
111.4
309.7
368.8
468.5
478.4
390.0
356.5
953.9
1018.1
1000.4
444.8
1283.8
309.1
212.9
780.5
46.1
52.7
465.0
587.3
92.2
1020.3
392.9
478.
389.
1065.
445.
1981
X
Y
51.1
107.6
303.3
362.3
461.3
582.9
89.8
390.4
362.0
951.1
1015.6
998.6
1063.6
446.9
394.1
323.1
398.0
309.1
213.3
778.6
CO
OO
CNJ
94.7
1025.3
391.9
324.0
404.7
COORDINATES
1980
X
Y
O
O
O
on
002
003
004
005
006
007
OlO
on
012
014
016
1979
309.
79-80
2.1
1.8
3.5
2.5
5.0
1.0
80-81 79-80
1.8
4.0
4.7
2.9
1.2
3.3
6.7
7.0
7.0
7.4
5.3
2.2
.98
6.9
64
APPENDIX C
• 1
AVERAGE RATE OF MOVEMENT FOR ONE YEAR BASED
ON THE RATE OF MOVEMENT FOR 1979-1981
\
65
APPENDIX C
Movement Rates. Data is in meters per year.
STAKE
NO.
MP006
MP007
MP008
MP009
MPOlO
MPOll
MPOl 2
MPOl 3
MPOl 4
.1
3.0
3.3
3.5
3.4
4.0
4.1
4.9
5.2
4.8
5.2
5.2
3.7
2.9
3.2
3.2
3.3
3.5
3.9
3.3
3.7
STAKE. MOVEMENT
NO.
CM
CM
UCOOO
UC003
UC004
UC005
UC006
UC007
UC008
UC009
UCOlO
UCOll
UCOl 3
UCOl 4
MOVEMENT -
LCOOl
LC002
.31
LC005
2.3
LC006
2.8
LC007
2.5
LC008 . 3.1
3.1
LC009
LCOlO
2.9
LCOll
2.5
LCOl 2
2.6
LCOl 3
2.7
001
002
003
004
005
006
007
010
on
012
014
016
2.1
1.7
3.4
3.5
3.5
3.7
4.7
2.7
5.0
1.1
.5
3.5
k
■V ">■•••'■
MAIN L ia
N378
J6368
cop.2
Johnson, R, F.
Ice movement and
structural characteristic:
of the Cathedral Glacier
System, Atlin Provincial
Park, British Columbia
y
,„