Deck 13: Glaciers and Glaciation

Question 1

Under what conditions do large crevasses develop in glaciers? What forces act to produce them, and where in the glacier are they found? What happens if a glacier descends over a steep precipice?

Answer 1

Crevasses develop where glaciers flow over an increase in the slope of the underlying surface or where they flow around a corner. The ice is stretched due to tensional forces. The crevasses open and extend down to the zone of plastic flow. If a glacier descends over a steep precipice, the crevasses break up the ice into a jumble of blocks and spires, and icefall develops.

Question 2

What are the zone of accumulation, zone of wastage (or ablation), and firn limit?

Answer 2

The upper part of a glacier is the zone of accumulation, where the addition of snow exceeds losses and the surface is perennially snow covered. The lower part of a glacier is the zone of wastage (or ablation) where snow is lost from melting, sublimation, and calving of icebergs in excess of the amount that zone accumulates. Snow accumulates in winter but melts in spring and summer. The elevation to which snow recedes during the wastage season is the firn limit.

Question 3

What are kettles, and how do they form?

Answer 3

Kettles are circular to oval depressions, sometimes containing small lakes, found on outwash plains, valley trains, or end moraines. They form when a block of ice, left by a retreating glacier, is partly or wholly buried, which subsequently melts, leaving a depression.

Question 4

Describe differences in flow rates within a valley glacier.

Question 5

Describe the main way that glaciers move. In which situations is this essentially the only type of flow a glacier will undergo?

Question 6

What was the Little Ice Age? What caused the famines?

Question 7

What are glaciers? How do they act as agents of erosion, transportation, and deposition?

Question 8

Under what conditions will the firn limit remain the same from year to year? Under what conditions will it change? What happens if the firn limit moves upward year after year?

Question 9

What are the different types of moraines: end moraines, ground moraines, recessional moraines, lateral moraines, and medial moraines?

Question 10

Describe valley glaciers.

Question 11

How and where do glaciers form?

Question 12

How do continental glaciers differ from valley glaciers?

Question 13

Describe the conditions that would make a valley glacier flow faster.

Question 14

What is the lesser way that glaciers flow, and what facilitates this movement? In which type of glaciers is this flow more important?

Question 15

What conditions are needed for glaciers to form and be maintained? As a result of these conditions, where are glaciers found?

Question 16

How does the Milankovitch theory explain intermediate-term climatic events like the Pleistocene glaciation? According to Milankovitch, variations in what three parameters of Earth's orbit were responsible for the onset of Pleistocene glaciation?

Question 17

What evidence of their passage do glaciers leave on bedrock?

Question 18

Explain the origin of varves and their significance in the chronologies of glacial lake deposits.

Question 19

What is the difference between ice caps and continental glaciers?

Question 20

What is glacial drift, and how does it differ from glacial till?

Question 21

What causes the rate of flow of a glacier to flow more rapidly?

Question 22

Why do continental glaciers generally flow more slowly than valley glaciers?

Question 23

Why is the velocity of valley glaciers slower along valley walls than in the center of the glacier?

Question 24

What does the term glaciation mean?

Question 25

How can you tell a river valley from a glacial valley if there is no glacier within the valley?

Question 26

Under what conditions can glaciers exist in the equatorial latitudes?

Question 27

What is the budget of a glacier, and when is the budget considered balanced?

Question 28

What is a fiord, and how does one form?

Question 29

What is a glacial surge?

Question 30

Is ice a mineral? Explain.

Question 31

If glacial ice were considered a rock, what type of rock would it be, and why?

Question 32

Under what conditions does a glacier advance?

Question 33

What is a hanging valley, and how does one form?

Question 34

What are dropstones, and what do they indicate?

Question 35

What are some of the characteristics of large ice-scoured plains, such as those of the Canadian Shield region?

Question 36

What are eskers, and how do they form?

Question 37

How does a terminal moraine differ from a recessional moraine?

Question 38

How does the water bound in glaciers eventually reenter the hydrologic cycle?

Question 39

How can the boundary between the zones of accumulation and wastage on a glacier be located during the spring and summer?

Question 40

Briefly explain the origin of drumlins.

Question 41

Elongated, spoon-shaped hills that have been shaped by an overriding glacier are called ____________________.

Question 42

The Matterhorn in Switzerland is a glacial ____________________ landform known as a(n) ____________________.

Question 43

The three stages involved in the formation of a glacier are the precipitation of ____________________; the formation of ____________________ by partial thawing, refreezing, and crystallization; and compaction and recrystallization to produce ____________________ ____________________.

Question 44

The presence of ____________________ in the upper 40 m or so of a glacier indicates that this portion behaves not as a plastic but as a(n) ____________________ solid.

Question 45

When snow thaws and refreezes, which results in a loss of air and pore spaces, the result is ____________________.

Question 46

The process by which ice evaporates directly from the surface of a glacier is known as ____________________.

Question 47

An ice mass of compacted and recrystallized snow that flows under its own weight on land is called a(n) ____________________.

Question 48

Finely laminated, alternating light and dark layers of sediment deposited in a glacial lake are known as glacial ____________________.

Question 49

In general, rates of glacial flow are greatest in the zone of ____________________.

Question 50

The fact that the Earth's orbit around the sun changes over time is called ____________________.

Question 51

Any sediment deposited as a result of glacial activity is known as glacial ____________________.

Question 52

The fine-, clay-, and silt-sized particles that result from glacial pulverization of rock are known as ____________________.

Question 53

Glaciers move primarily by ____________________ flow.

Question 54

A glacier that is now longer flowing is called a(n) ____________________ glacier.

Question 55

The distal end or edge of the glacier is called its ____________________.

Question 56

The zone of wastage (ablation) is the portion of a glacier where ____________________ exceed ____________________.

Question 57

The present glacial landscapes mainly formed during an Ice Age that lasted from approximately____________________ years to ____________________ years ago.

Question 58

The two major types of glaciers are ____________________ and ____________________.

Question 59

The zone of ____________________ is the portion of a glacier where additions exceed losses.

Question 60

The climatic event that began with cooling in about A.D. 1300 and lasted until the middle-1800s is known as the Little ____________________.

Question 61

A glacier begins to flow when the ice reaches a critical thickness of about:

A) 100 meters.
B) 40 meters.
C) 20 meters.
D) 10 meters.
E) 5 meters.

Question 62

The terms glacier and permanent snowfield are synonymous.

Question 63

The terms valley glacier and mountain glacier are synonymous.

Question 64

Continental glaciers are presently found on:

A) Greenland.
B) Antarctica.
C) Alaska.
D) Greenland and Antarctica.
E) Greenland, Antarctica and Alaska.

Question 65

The ice ages are caused by:

A) the drift of the continents.
B) the eruption of supervolcanoes.
C) the sunspot cycle.
D) minor changes in Earth's rotation and orbit.
E) variations in solar output.

Question 66

Glacial till is:

A) any sediment deposited as a result of glacial activity.
B) boulders transported long distances and deposited by glaciers.
C) an elongated, spoon-shaped hill that has been shaped by an overriding glacier.
D) unstratified sediment deposited directly by a glacier.
E) a lake within an outwash plain.

Question 67

In a cross-section of a glacier, the greatest flow velocities occur:

A) at the surface.
B) in the few tens of meters below the surface.
C) in the few tens of meters above the base.
D) at the base.
E) in the center of the flow.

Question 68

A glacial landform that forms at the head of glacial valleys or troughs that has as a bowl-shaped appearance is called a(n):

A) horn.
B) esker.
C) kame.
D) arête.
E) cirque.

Question 69

Short-term climatic events, such as the Little Ice Age, may be caused by:

A) variations in solar energy.
B) large volcanic eruptions.
C) Milankovitch cycles.
D) variations in solar energy AND large volcanic eruptions.
E) no one really knows.

Question 70

Glaciers today cover about 10% of Earth's land surface.

Question 71

A lake formed within a cirque is called a(n):

A) arête.
B) esker.
C) tarn.
D) fiord.
E) drumlin.

Question 72

The largest existing glacier is located in:

A) Greenland.
B) Alaska.
C) The Alps.
D) Patagonia.
E) Antarctica.

Question 73

A glacial landform with steep-walled, pyramidal peaks formed by headward erosion of glaciers on at least three sides is a(n):

A) horn.
B) esker.
C) kame.
D) terminal moraine.
E) cirque.

Question 74

The Pleistocene Ice Age ended:

A) 2.6 million years ago.
B) 10,000 years ago.
C) 1300 years ago.
D) 200 years ago.
E) It still hasn't ended.

Question 75

The only continent that does not presently have glaciers is:

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

Question 76

Earth's orbit varies from nearly a circle to an ellipse and back again in about:

A) 1,000,000 years.
B) 100,000 years.
C) 10,000 years.
D) 1,000 years.
E) 100 years.

Question 77

Glaciers are geologically important because they erode, transport, and deposit lot of material.

Question 78

The Little Ice Age ended in the mid- to late-1800s.

Question 79

The reason that Earth is now closest to the Sun in January, but will be closest in July in 11,000 years, is:

A) orbital eccentricity.
B) changes in axial tilt.
C) precession of the equinoxes.
D) gravitational attraction to the sun.
E) gravitational attraction to the moon.

Question 80

Straight scratches on rock surfaces created by glacial abrasion are known as:

A) rock flour.
B) glacial striations.
C) glacial till.
D) varves.
E) moraines.