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Geology 111 > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

What is a glacier?

A

A large, long lasting mass of ice, formed on land by the compaction and recrystallization of snow, which moves because of its own weight.

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2
Q

What are the two types of glaciers?

A

Alpine

Continental

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3
Q

What is a valley glacier?

A

A glacier that forms high up in a valley and flows from top to bottom.

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4
Q

What is an ice sheet?

A

A glacier covering a large area of land usually more than 50, 000 square kilometers.

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5
Q

What is an ice cap?

A

A glacier converting a relatively small area of land but not restricted to a valley.

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6
Q

What is ablation?

A

The loss of the glacial ice or snow by melting evaporation or breaking off into icebergs.

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7
Q

What is an advancing Glacier?

A

Glacier with a positive budget, so that accumulation results in the lower edges being pushed outward and downward.

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8
Q

What is a receding Glacier?

A

A glacier with a negative budget, which causes the glacier to grow smaller as its edges melt back.

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9
Q

What is the zone of accumulation?

A

The top portion of a glacier with a perennial snow cover. Were the glacier grows the most.

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10
Q

What is the zone of ablation

A

The portion of a glacier in which ice is lost.

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11
Q

What is the line of equalibriam?

A

The line between the zone of accumulation and ablation

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12
Q

What is the Terminus of a glacier?

A

The lower edge of a glacier.

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13
Q

What is basal sliding?

A

Movement in which the entire glacier slides along a single body on its base over the underlying rock.

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14
Q

What is the rigid zone?

A

The upper part of a glacier in which there is no plastic flow.

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15
Q

What is a crevasses.

A

Open fissures in a glacier caused by the bending of ice as it goes over steps often hundreds of meters deep.

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16
Q

What is an outlet Glacier?

A

Where mountain ranges are higher than the ice sheet, the ice flows between mountains as valley glaciers, known as outlet glaciers.

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17
Q

What percentage of the earths surface is covered by glaciers?

A

10%

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18
Q

What is an icestream?

A

A zone of ice that has considerably higher flow rate than the adjoining ice.

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19
Q

What are the variables in the movement of a valley glacier down slope?

A

1: Ice temperature
2: Glacier Thickness
3: Steepness of the slope the glacier is on

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20
Q

What is plucking known as?

A

When a glacier freezes and cracks the rock underneath and then plucks out the chunks as fragments.

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21
Q

What is striation when referring to glaciers?

A

The scratch lines of the underlying rock usually smooth. It indicates what direction the ice was flowing.

22
Q

What is rock flour?

A

A powder of fine fragments of rock produced by glacial abrasion.

23
Q

What does a valley in a U shape tell you about the valleys history?

A

It was formed by Glacial Erosion.

24
Q

What is a hanging Valley?

A

A side glacier that did not erode as much as the main glacier leaving an abrupt drop of were the two glaciers met.

25
Q

What are truncated spurs?

A

A glacier is to sluggish to make rounded turns so its corners are usually sharp.

26
Q

What are rock basin lakes?

A

Lakes that are formed from glaciers flowing down hill and certain parts of the rock being more resistant to erosion than others and steps are formed.

27
Q

What is a cirque?

A

A steep-sided amphithere like hollow carved into a mountain at the head of a glacial valley.

28
Q

What kind of erosion do ice sheets tend to produce?

A

Rounded topography as well as knogs and occasionally trenches.

29
Q

What is till?

A

Unsorted and unlayered rock debris carried by a glacier.

30
Q

What is an erratic?

A

An ice-transported boulder that does not derive from bedrock near its present site.

31
Q

What is moraine

A

A gody of till either being carried on a glacier or left behind after a glacier has receded.

32
Q

What is Lateral Moraines

A

low, ridgelike pile of till along the side of a glacier.

33
Q

What is end Moraine

A

Till that is piled up at the the front edge of a glaciers because it has not moved in a long time.

34
Q

What is commonly produced by the movement of an ice sheet?

A

Rounded Knobs
Striated Bedrock
Grooved Bedrock

35
Q

How does an ice sheet round and streamline mountains?

A

By flowing over a completely covered mountain range.

36
Q

What is a Medial Moraine

A

when there are rows of till built up between rows in a glacier.

37
Q

What are drumlins?

A

A long, streamlined hill made of till.

38
Q

What is Outwash?

A

Material deposited by debris-laden meltwater from a glacier.

39
Q

What are eskers?

A

A long, sinuous ridge of sediment deposited by glacial meltwater usually they are streams that existed under a glacier.

40
Q

What is a kettle?

A

A depression caused by the melting of a stagnant block of ice that was surrounded by sediment.

41
Q

What is a varve?

A

Two thin layers of sediment, one dark and the other light in color, representing one years deposition in a lake.

42
Q

What is the Theory of Glacial Age?

A

At times in the past, colder climates prevailed during which significantly more of the land surface of earth was glaciated than at present.

43
Q

When did the last of the great North American ice sheets melt away from Canada?

A

Less than 10,000 years ago.

44
Q

What Epoch is the glacial age associated with?

A

Pleistocene

45
Q

What was the largest ice sheet during the glacial age?

A

The Laurentide Ice Sheet.

46
Q

What is a pluvial lake?

A

A lake formed during an earlier time of abundant rainfall.

47
Q

Fiord

A

A coastal inlet that is glacially carved valley, the base of which is submerged.

48
Q

What evidence supports the snowball earth hypothesis?

A

Tillites deposited at the equator.

49
Q

Average annual temperatures during the height of a glacial age are about how much cooler than today?

A

5 Degrees

50
Q

how old is the oldest glacian that we have evidance for?

A

2.3 billion.

51
Q

What are indicators for alpine glaciations being much more extensive throughout the world during the glacial ages than they are now?

A

1: Cirques and other features typical of valley glaciers are found in places that are no longer glaciated.
2: Small glaciers in the rocky mountains were once several kilometers in length.

52
Q

What is Louis Agassiz responsible for?

A

1: Publishing a discourse arguing that switzerland was entirely glaciated in the past
2: concluding that a great glacier had covered most or all of europe.
3: Finding evidence of past glaciation of the british isles
4: Finding similar evidence of past glaciation of North America.

Geology 111 (22 decks)

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