Deck 17: Glaciers and Ice Ages

Question 1

Loess is a soil formed by:

A) meltwater deposits of sand and gravel.
B) wind- blown deposits of outwash silt.
C) glacial advances over previously deposited moraines.
D) a mixture of sand and clay at the bottom of a meltwater lake.

Answer 1

B

Question 2

All of the following landforms would be absent without the work of glaciers EXCEPT:

A) Niagara Falls.
B) Cape Cod.
C) the Great Lakes.
D) the Rocky Mountains.

Answer 2

D

Question 3

The principal effect of Milankovitch's astronomical cycles is that:

A) when the cycles are opposed, wintertime radiation increases, causing increased precipitation.
B) when the cycles coincide, summertime radiation is reduced.
C) when the cycles are opposed, solar radiation is at a minimum.
D) when the cycles coincide, winters are much more severe.

Answer 3

B

Question 4

Which of the following statements about glacial flow is NOT true?

A) In the accumulation zone, ice flows down toward the glacier's bed.
B) In basal sliding, a glacier slides along its bed on a film of water.
C) In extremely cold climates, glaciers flow more by basal sliding than by internal deformation.
D) In internal deformation, ice flows because crystals slide past one another under pressure.

Question 5

In a confined glacier, the terminus of a glacier advances downslope under which conditions?

A) Accumulation is less than ablation.
B) Accumulation is greater than ablation.
C) Accumulation and ablation are equal.
D) All of the above.

Question 6

All of the following statements concerning Glacial Lake Missoula are true EXCEPT:

A) the lake was as large as present- day Lake Superior.
B) the lake was at least 300 meters deep.
C) the last flood took place about 13,000 years ago.
D) the lake was impounded by the Purcell Ice Lobe.

Question 7

All of the following describe the most recent extensive glaciation in North America EXCEPT:

A) a sheet of ice covered more than 6 million square miles of the continent.
B) a warming trend began 20,000 years ago that ultimately brought the ice age to an end.
C) the ice sheet stripped regolith 15-25 meters deep from regions of Canada and the United States.
D) the ice sheet stretched the full breadth of southern Canada and the northern United States.

Question 8

By the year 2030, global warming may have raised sea level as much as:

A) 3- 5 meters.
B) 0.5- 1.0 meter.
C) 0.5 meter.
D) 1- 2 meters.

Question 9

All of the following statements concerning extensive glaciation during the Permian Period are true EXCEPT:

A) the areas that retain evidence of Permian glaciation were at that time near the South Pole.
B) Permian glaciation was initiated after the breakup of Pangaea.
C) evidence of this glaciation may be found in Australia, South America, India, and South Africa.
D) this glaciation occurred about 245-286 million years ago.

Question 10

The 700 million year old tillite found worldwide indicates an Ice Age centered in the:

A) alpine regions.
B) equatorial regions.
C) desert regions.
D) polar regions.

Question 11

Recent discoveries about the ice ages that developed from ice- core studies include all of the following EXCEPT:

A) ancient volcanic catastrophes can be confirmed and dated by ice- core analysis.
B) the ice- age atmosphere was more windy than the atmosphere today.
C) the atmospheric CO2 content was significantly lower during the ice ages than it is today.
D) isotopes of CO2 trapped in glacial ice provide a geochemical thermometer of ice- age temperatures.

Question 12

The current glaciation on Mars probably consists of:

A) thin, seasonal polar ice caps consisting of frozen CO2.
B) small valley glaciers that recede in summer due to extensive water evaporation. extensive linear glaciers that form a network of canals that cover much of the planet.
C) continental ice sheets only half the size of the Earth's ice- age glaciation.

Question 13

The glacier's zone of accumulation can be recognized by:

A) rocks and boulders melting from the ice.
B) snow from the previous winter covering the glacier ice.
C) icebergs calving into a lake.
D) exposed, bare ice.

Question 14

Many geologists have concluded that the development of ice ages requires:

A) all of the Earth's continents to mass together near the poles, and dramatic shifting of the climatic belts.
B) relatively high- elevation landmasses near the equator and relatively low- elevation landmasses near the poles.
C) sizable landmasses near the poles, and land surfaces with relatively high elevation.
D) massive amounts of near polar waters, and an increased distance between the Earth and the Sun.

Question 15

A roche mountonne´e can indicate the direction of glacial flow from all of the following features EXCEPT:

A) its symmetrical sides are parallel to glacial flow.
B) the down- glacier side is the most heavily quarried.
C) the up- glacial side is usually well striated.
D) the up- glacier side is steep and jagged.

Question 16

For approximately the last 150 years, the Earth's average global temperature has:

A) remained relatively constant.
B) decreased.
C) increased.
D) alternated between warming and cooling.

Question 17

A submerged U- shaped valley is called a(n):

A) col.
B) are^te.
C) hanging valley.
D) fjord.

Question 18

Tillite is:

A) a well- sorted sediment deposited as a glacier advances.
B) a sedimentary rock produced by lithification of till.
C) a metamorphic rock formed from glacial till that has been subjected to high pressure.
D) an unsorted moraine.

Question 19

All of the following statements concerning permafrost are true EXCEPT:

A) it is found in high- latitude periglacial environments.
B) it consists of soil, sediments, and bedrock that is consistently below freezing.
C) it is usually very shallow, and seldom over 100 feet deep.
D) it underlies about 25% of the Earth's land surface.

Question 20

Which of the following statements about striations is NOT true?

A) Abrasion is most accelerated in subpolar zones.
B) Prolonged abrasion by fine, gritty rocks may produce a smooth polished finish on the underlying bedrock.
C) The abrading stones may eventually be pulverized to form glacial flour.
D) Formation of striations is facilitated by ice movement within accumulation areas up- glacier of the equilibrium line.

Question 21

In a confined glacier, the glacial ice tends to flow from the accumulation zone toward the ablation zone under which conditions?

A) Accumulation is less than ablation.
B) Accumulation is greater than ablation.
C) Accumulation and ablation are equal.
D) All of the above.

Question 22

The "Little Ice Age":

A) was the Earth's first known ice age, and occurred during the Precambrian Era.
B) refers to the present Quaternary ice age, which, in geologic terms, has been shorter than many of the Earth's earlier ice ages.
C) was a period of cooler global temperatures from about 1300 to 1850 A.D. and included glacial expansion in mid- latitude mountain ranges.
D) was the last major Pleistocene episode of glaciation, and ended about 10,000 years ago.

Question 23

Salinity- driven currents are considered a major factor in ice- age glacial expansions because:

A) salt lowers the freezing point of water.
B) their heat- carrying capacity during nonglacial times transports heat from the lower latitudes to the higher latitudes.
C) dense saline water has a higher albedo than less saline water.
D) dense saline currents are more able to transport large blocks of ice.

Question 24

In the alpine highlands of North America, Europe, and Asia, the most effective geologic shaping process would be:

A) wind erosion.
B) stream erosion.
C) erosion by glaciers.
D) mass- movement.

Question 25

All of the following landforms were shaped by continental ice sheets EXCEPT:

A) the mountain peaks of Glacier National Park.
B) the Great Lakes.
C) the Puget Sound of Washington.
D) the Finger Lakes of New York.

Question 26

Till appears different from outwash in that:

A) till is less sorted and stratified than outwash.
B) till is better sorted and stratified than outwash.
C) till contains only smaller particles while outwash contains both small and large rock fragments.
D) till is darker in color than outwash.

Question 27

The term "glacial drift" applies to:

A) glacial deposits that are carried by meltwater into nearby streams.
B) glacial deposits of very fine particles that eventually become wind- blown.
C) all glacial deposits, collectively.
D) the redistribution of glacial deposits by consecutive advances.

Question 28

Which of the following statements about glaciers is NOT true?

A) Valley glaciers flow in preexisting stream valleys.
B) Piedmont glaciers begin as alpine glaciers but flow onto an adjacent lowland.
C) Continental ice sheets are confined glaciers that move over low- lying continental areas.
D) Cirque glaciers create and occupy semicircular basins on mountain sides.

Question 29

The term "albedo" refers to:

A) the percentage of solar radiation that is absorbed by the Earth's atmosphere.
B) the percentage of solar radiation that reaches the Earth's surface.
C) the percentage of solar radiation that is reflected away from the Earth's surface.
D) the percentage of solar radiation that is absorbed by the Earth's surface.

Question 30

During major glaciations, sea level was 130 meters lower than at present, facilitating land migration between:

A) North America and Asia.
B) Asia and Australia.
C) Europe and North America.
D) Africa and South America.

Question 31

Glacial ice forms for all of the following reasons EXCEPT:

A) air circulating through the spaces in accumulated snowpacks causes some of the snow to sublimate.
B) winter low temperatures probably contribute less to glacial growth than cool, cloudy, brief summers.
C) water produced by pressure melting migrates to open spaces in the snowpack and refreezes.
D) most precipitation in glacial areas consists of hard- packed snow pellets called firn.

Question 32

A medial moraine forms:

A) along the sides of a glacier.
B) where two valley glaciers merge.
C) beneath a glacier in a sinuous ridge.
D) where a glacier terminus advances beyond a recessional moraine.

Question 33

All of the following theories have been rejected as explanations of the triggering mechanism for continental glaciation EXCEPT:

A) plate motions, because they are too slow to account for repeated cycles of glacial advances and retreats.
B) large meteorite impacts, because they are not periodic and their effects are short- lived.
C) volcanism, because it does not occur at regular intervals and its effects are too brief.
D) orbital mechanics, because its effects are too slight to account for global climatic changes.

Question 34

A terminal moraine forms when:

A) accumulation and ablation are equal.
B) accumulation is less than ablation.
C) accumulation is greater than ablation.
D) All of the above.

Question 35

Glaciers are classified by:

A) their size.
B) their degree of confinement.
C) their rate of growth.
D) the rate at which their ice flows.

Question 36

The marine record of ancient climatic changes is obtained by all of the following methods EXCEPT:

A) isotope and fission- track dating of ash layers.
B) geomagnetic- stratigraphy dating of deeper cores.
C) carbon- 14 dating of organic material in deep- sea mud cores.
D) observing fossil foraminifera whose size was dependent on temperature.

Question 37

Glacial surges are caused by:

A) rapid internal deformation of the ice.
B) a large buildup of snow in the zone of accumulation.
C) the weight of sediment trapped within the glacier.
D) an accumulation of water at the base of the glacier.

Question 38

Which of the following explains the rapid disappearance of eskers?

A) They are being eroded by the flooding of old meltwater stream beds.
B) They are being mined for sand and gravel.
C) They are being leveled for housing developments.
D) They are being mined for valuable ore.

Question 39

Which of the following statements about drumlins is NOT true?

A) Drumlins are composed of unsorted, unstratified glacial drift.
B) Drumlins are oriented parallel to terminal moraines.
C) Drumlins are formed by continental ice sheets rather than by alpine glaciers.
D) Drumlins are elongated, asymmetrical hills.

Question 40

The best records of land- based glacial climates come from:

A) speleothems in tropical caves.
B) glacial sediments.
C) mammal fossils in permafrost.
D) fossil pollen preserved in lake sediments.

Question 41

Describe the formation of glacial ice.

Question 42

Given that the deepest carved channels in the scablands are nearly 250 meters in depth, the height of the floodwaters must have been at least:

A) 1000 meters.
B) 100 meters.
C) 500 meters.
D) 250 meters.

Question 43

The difference between a cirque and a tarn is:

A) a cirque is a basin made by a glacier while a tarn is a mountain pass between two cirques.
B) a tarn is a basin made by a glacier while a cirque is a sharp ridge between two tarns.
C) a cirque is at the zone of accumulation while a tarn is at the zone of ablation.
D) a cirque is a basin made by a glacier while a tarn is a lake within a cirque.

Question 44

How are human activities having an effect on global temperatures?

Question 45

How does plate tectonics contribute to the initiation of an ice age? In what ways can plate tectonics not account for the ice ages?

Question 46

What are eskers, and how do they form?

Question 47

Once astronomical factors initiate a period of glaciation, how does albedo reinforce global cooling?

Question 48

List and describe the different classifications of glaciers.

Question 49

Which of the following statements concerning the most recent ice age is NOT true?

A) In some places in North America, ice was 2.5 miles thick during the last major ice advance.
B) The last glacial advance occurred during the Pleistocene Epoch which ended about 10,000 years ago.
C) About 20,000 years ago, ice covered roughly 50% of the Earth's land surface.
D) We now live in a warm interglacial period of an ice age.

Question 50

Discuss the glacial budget.

Question 51

Describe the evidence for past and present glaciation on Mars.

Question 52

List the Earth's past episodes of continental glaciation.

Question 53

Describe the factors beyond the initial snowfall that influence the formation and growth of glaciers in mountainous regions.

Question 54

Which of the following was NOT an effect on flora and fauna during ice- age glaciation?

A) Many species living as much as 2000 miles from the ice were forced into accelerated competition for resources.
B) Many species of both plants and animals were able to migrate.
C) Many species were able to adapt to living on glacial ice.
D) Many species that existed during ice ages became extinct.

Question 55

Describe how the Earth's temperatures have fluctuated over the past 65 million years.