GEOLOGY 12
CHAPTER 17 WORKSHEET
GLACIERS
Name __________________
Part A Multiple Choice
1.
The most important requirement for a glacier to form is
a. that snow accumulates on gentle, north facing slopes
b. that winter snowfall exceeds summer melting for several years
c. that heavy snows fall in high latitude or polar regions
d. that temperatures drop at least 10ºC
2.
The presence of crevasses in the upper portion of a glacier is evidence that
a. the glacier is moving by means of slip along meltwater at its base
b. the glacier is moving entirely by internal deformation
c. the ice has reached the critical thickness of crevasses to form
d. the upper portion of the ice is behaving in a brittle fashion, above the more plastic
layers below
3.
The main reason that glaciers flow is because
a. large bodies of ice or snow are inherently unstable
b. they always form on slopes they can slip down
c. the weight of the accumulated ice and snow causes the glacier to behave in a plastic
manner
d. all surface agents of erosion move under the influence of gravity
4.
The Hubbard Glacier in Alaska is experiencing a period of glacial surge. What does this
mean?
a. The glacier is retreating very rapidly.
b. The glacier is receiving exceptionally high amounts of snowfall and undergoing no
ablation.
c. The glacier is advancing at a fast rate by means of rapid flow.
d. The glacier is calving at a very fast rate.
5.
The front edge of a particular glacier has remained in the same position for several years.
What can you say about the balance of ablation and accumulation?
a. Over time, accumulation is greater than ablation.
b. Over time, ablation is greater than accumulation.
c. The rates of ablation and accumulation are balanced.
d. Nothing!
6.
Which characteristic below is true about glacially eroded sediments?
a. They undergo little alteration from the original chemical and mineralogical character of
the parent rock.
b. They are well-sorted by size as they are carried by the glacier.
c. They tend to be well-rounded by the abrasion of the glacier.
d. They are restricted to a narrow size range of fine silt to sand-sized particles.
7.
Which feature would be the best indicator that a valley was formerly occupied by a glacier?
a. presence of an arête in the valley
b. the valley is U-shaped
c. presence of pluvial lake sediments in the valley
d. presence of poorly sorted sediments in the valley
8.
What must occur for an active glacier to acquire several medial moraines?
a. The glacier must flow over previously glaciated terrain.
b. The glacier must be joined by several tributary glaciers, each of which has lateral
moraines.
c. The glacier must distribute the sediments of its own lateral moraines into a number of
stripes of moraine sediments.
d. The glacier must flow through an area with a high rate of rock fall to scatter sediments
on the glacier’s surface.
9.
The best way to tell the farthest extent of a glacier after it is gone is to find
a. a cirque
b. striations
c. a glacial erratic
d. a terminal moraine
10. Which of the following glacial features would be the best clue for determining the direction
a former continental glacier flowed?
a. striations on bedrock
b. ground moraine
c. erratics
d. arêtes
11. Which glacial features below would you look for in an outwash plain of a former glacier?
a. hanging valleys and tarns
b. erratics and cirques
c. kettles and eskers
d. horns and arêtes
12. Which of the ideas below provide an explanation for the ice ages, without relying on global
cooling, in one form or another?
a. movement of continents associated with plate tectonics
b. variations in the tilt of the earth's rotational axis
c. dust and debris in the atmosphere from intensive and frequent volcanic eruptions
d. reduction in solar radiation due to sunspot activities or related solar events.
Part B Fill in the Blank
1.
Nearly three-fourths of the world's fresh water is stored in _____________________.
2.
A _____________________ is a mass of ice that moves under its own weight on land.
3.
Glaciers can exist in areas of high latitude or high ______________________.
4.
One requirement for a glacier to form is that winter snowfall must exceed
__________________ ___________________.
5.
Coarse granular ___________________ is formed from snow in the process of
transforming snow into glacial ice.
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6.
______________________ glaciers, or valley glaciers, form in mountainous regions,
usually at high altitudes.
7.
Ice caps or sheets that cover large areas with glacial ice are also known as
__________________________ glaciers.
8.
A glacier moves more slowly at its base largely because of ______________________
with the underlying rock.
9.
The uppermost layers of a glacier behave in a brittle fashion, fracturing to create
______________________.
10. Ice loss by melting, evaporation or calving is known as ______________________.
11. A glacier is ______________________ when the rate of accumulation is greater than the
rate of ablation.
12. A glacier is ______________________ when the rate of ablation is greater than the rate of
accumulation.
13. Rock fragments frozen into the ice of a glacier cause erosion by
______________________ at the base of the glacier or along valley walls
14. The powdery silt-sized sediment created by continued grinding of glacial sediments is
known as ______________________.
15. Glaciers deposit very poorly-sorted sediments known as __________________.
16. The process of ______________________ enables glaciers to pick out and carry away
chunks of bedrock.
17. When a tributary glacier flows into a main glacier at a lower altitude a _________________
___________________ may exist when the glaciers melt away.
18. A ___________________ is the rounded or bowl-like depression at the head of an alpine
glacier.
19. Alpine glaciers that flow in parallel valleys may create a knife like ridge between the
valleys; this ridge is known as an ___________________.
20. Parallel grooves or scratches in bedrock produced by a glacier are called
______________________ and can be used to tell which direction the ice flowed.
21. The debris that collects along the sides of a valley glacier is deposited in a
______________________ moraine
22. The moraine that marks the farthest extent of a glacial advance is known as the
______________________ moraine.
23. Continental glaciers flowing over previously deposited ground moraine may shape the
moraine sediment into elongated oval hills or mounds called ______________________.
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24. Water-deposited glacial sediments are known collectively as glacial _________________.
25. Wind-deposited rock flour is known as ___________________.
26. The fine layers in glacial lake sediments are known as ___________________. These
layers are thought to represent seasonal depositional variations.
27. Advances of ice sheets during ice ages are accompanied by a _________________ in the
sea level.
28. Cooling of only _____ to _____ºC is probable enough to cause an ice age.
29. One external cause for ice ages relates to variations in the __________________ of the
earth's axis as it rotates.
30. Dust and ash produced by __________________ _______________ could cause global
cooling sufficient to initiate an ice age.
31. During the period known as the "Little ice Age", global temperatures were _____________
than they are today.
Part C True or False
1.
T
F
Glaciers exist only in cold polar regions where temperatures are low year round.
2.
T
F
Complete conversion of snow to glacial ice takes 20 years in most settings.
3.
T
F
Continental ice sheets, though fewer in number than alpine glaciers, cover much
more land with ice.
4.
T
F
Glaciers typically flow very slowly, except during a surge, when flow rates may be
as high as 15-30 meters per day.
5.
T
F
Internal deformation is most obvious in upper portions of a glacier, where plastic
flow is exhibited by crevasses.
6.
T
F
When a glacier retreats, the ice flows backwards.
7.
T
F
Since about 1940, most glaciers have been advancing.
8.
T
F
Glacial ice alone is effective at scraping and souring the rocks over which it flows.
9.
T
F
Lateral moraines are used to determine the farthest advance of a glacier.
10.
T
F
The Pleistocene Ice Age is the only known occurrence of widespread glaciation
of continents throughout geologic history.
11.
T
F
Sunspot activity, which causes variations in the sun's intensity, is a likely cause
for the ice ages.
12.
T
F
Dust in the atmosphere causes cooling by blocking out incoming solar radiation.
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Part D Matching
Match the glacial feature and its description.
1.
_____ lateral moraines
A. high peak, sculpted by several glaciers
2.
_____ erratic
B. hole or depression in outwash deposits
3.
_____ loess
C. large, out-of-place boulder
4.
_____ end moraine
D. small, rounded lake in a cirque
5.
_____ tarn
E. ridge of till at end of a glacier
6.
_____ esker
F. elongated, oval hills of till
7.
_____ striations
G. deposits of fine rock flour
8.
_____ kettle
H. till deposited along sides of a valley glacier
9.
_____ horn
I. scratches or grooves in bedrock
10. _____ medial moraine
J. ribbon of till as a stripe within a glacier
11. _____ drumlins
K. snakelike outwash ridge
Match the glacial feature with how it is formed.
12. _____ varves
A. eroded directly by ice
13. _____ erratic
B. deposited directly by ice
14. _____ loess
C. associated with meltwater deposits
15. _____ end moraine
D. deposited by wind
16. _____ tarn
17. _____ esker
18. _____ striations
19. _____ kettle
20. _____ horn
21. _____ medial moraine
22. _____ drumlin
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