Deck 13: Glaciers and Glaciation

Question 1

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

Answer 1

The Little Ice Age was a cooling trend that began about A.D.1300 and lasted from 1500 to the mid- or late-1800s.During this time,glaciers expanded,summers were cooler and wetter,winters were colder,and sea ice persisted for long periods in Greenland,Iceland,and the Canadian Arctic Islands.Famines were caused by cooler,wetter summers,which led to short growing seasons and several widespread famines.

Question 2

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

Answer 2

Varves are laminated silts and clays that are deposited in glacial lakes and marine waters beneath regions of fluctuating sea ice cover.The darker layers are deposited at the end of the summer season when the summer's life dies and becomes incorporated in the accumulating sediment.The lighter- and finer-grained layers are deposited during the winter when the water is still,lacking abundant life,and receiving little sediment.Thus,each light and dark pair represents one year's accumulation.

Question 3

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

Answer 3

Glaciers form where there is a lot of snowfall and temperatures are cold.Since temperatures are colder at higher altitudes and latitudes,these regions have glaciers if they receive enough snow.The mountains of California receive a lot of snow,but only very high mountains are cold enough to maintain glaciers.Glaciers cover the continents in the far north and south,e.g. ,Greenland and Antarctica.

Question 4

What evidence of their passage do glaciers leave on bedrock?

Question 5

What are the zone of accumulation,zone of wastage,and firn limit?

Question 6

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?

Question 7

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

Question 8

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

Question 9

Describe valley glaciers.

Question 10

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

Question 11

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 12

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

Question 13

What is the difference between ice caps and continental glaciers?

Question 14

Describe differences in flow rates within a valley glacier.

Question 15

What are kettles,and how do they form?

Question 16

How do continental glaciers differ from valley glaciers?

Question 17

What are glaciers? How are they as agents of erosion and deposition?

Question 18

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

Question 19

How and where do glaciers form?

Question 20

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 21

What are eskers,and how do they form?

Question 22

Under what conditions can glaciers exist in the equatorial latitudes?

Question 23

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

Question 24

What are dropstones,and what do they indicate?

Question 25

Is ice a mineral? Explain.

Question 26

What does the term glaciation mean?

Question 27

How does a terminal moraine differ from a recessional moraine?

Question 28

What is a glacial surge?

Question 29

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

Question 30

What is a fiord,and how does one form?

Question 31

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

Question 32

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

Question 33

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

Question 34

Under what conditions does a glacier advance?

Question 35

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

Question 36

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

Question 37

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

Question 38

Briefly explain the origin of drumlins.

Question 39

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

Question 40

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

Question 41

Glaciers move primarily by ____________________ flow.

Question 42

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

Question 43

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

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

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

Question 47

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

Question 48

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 49

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

Question 50

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

Question 51

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

Question 52

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

Question 53

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

Question 54

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

Question 55

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

Question 56

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

Question 57

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

Question 58

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

Question 59

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

Question 60

The two major types of glaciers are ____________________ and ____________________.

Question 61

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 62

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.

Question 63

The largest existing glacier is located in:

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

Question 64

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

Question 65

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

Question 66

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 67

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 68

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 69

Glaciers are geologically important because they erode,transport,and deposit so much material.

Question 70

Continental glaciers are presently found on:

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

Question 71

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 72

A glacial landform that forms at the head of glacial valleys or troughs is called a(n):

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

Question 73

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 74

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 75

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 76

The terms valley glacier and mountain glacier are synonymous.

Question 77

The terms glacier and permanent snowfield are synonymous.

Question 78

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

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

Question 79

The only continent that does not presently have glaciers is:

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

Question 80

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.