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geology > glaciers > Flashcards

glaciers Flashcards

1
Q

what are glaciers?

A

Thick masses of recrystallized ice

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2
Q

how much of the earth do glaciers cover?

A

10%

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3
Q

how much of the earth did glaciers cover during ice ages?

A

30%

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4
Q

what are characteristics of glaciers?

A

Last all year long
* Flow via gravity
* Mountain and continental

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5
Q

how do glaciers form?

A

snowfall accumulates
snow is turned into ice

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6
Q

how is snow turned into ice?

A

Snow is buried by later falls
* Compression reduces volume
* Burial pressure causes melting and recrystallization
* Snow turns into granular firn
* Over time, firn becomes interlocking crystals of ice

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7
Q

what are three conditions required for glacier formation?

A

Cold local climate (polar latitudes or high elevation)
* Snow must be abundant; more snow must fall than melts
* Snow must not be removed by avalanches or wind

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8
Q

what are the two categories of glacier?

A

Alpine (mountain)
Continental (Ice sheets)

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9
Q

what are the types of alpine glaciers?

A

Cirque glaciers
valley glaciers
ice caps
piedmont glaciers

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10
Q

what are cirque glaciers?

A

fill mountain top bowls

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11
Q

what are valley glaciers?

A

flow like rivers down valleys

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12
Q

what are ice caps?

A

cover peaks and ridges

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13
Q

what are piedmont glaciers?

A

spread out at the end of a valley

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14
Q

how do alpine glaciers flow?

A

from high to low elevation

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15
Q

what are continental glaciers?

A

Vast ice sheets covering large land areas

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16
Q

how do continental glaciers flow?

A

outward from the thickest part of the sheet

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17
Q

what are the two main continental glaciers?

A

Greenland
Antarctica

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18
Q

what is albedo?

A

The amount of light or radiation reflected by a surface.

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19
Q

can glaciers be stationary?

A

no

20
Q

3 conditions needed to form a glacier?

A

A cold local climate, abundant snow, and no snow removal by wind or avalanches.

21
Q

what are the two ways glaciers move?

A

Basal sliding and plastic deformation

22
Q

what is basal sliding?

A

The process of a glacier sliding due to meltwater at the base of a glacier.

23
Q

why does plastic deformation occur?

A

Ice cannot crack at certain pressure, so it will bend/fold.

24
Q

What forms at the surface of glaciers when it undergoes plastic deformation?

A

Crevasses because the upper zone is too brittle to flow.

25
Q

Why do glaciers move?

A

The pull of gravity is strong enough to make glaciers constantly flow.

26
Q

What depth can ice not crack at?

A

60m

27
Q

Why do glaciers move?

A

The pull of gravity is strong enough to make glaciers constantly flow.

28
Q

Why do continental glaciers move?

A

Ice spreads away from the centre of accumulation because the ice sheet is always thicker in the middle.

29
Q

What is the rate of glacial flow controlled by? (3 things)

A

The severity of slope angle,
amount of basal water,
the location of ice on the glacier.

30
Q

What is the zone of accumulation?

A

The area of net snow accumulation

31
Q

What is the zone of ablation?

A

The area of net ice loss.

32
Q

Where do the zones of accumulation and ablation meet?

A

The equilibrium line

33
Q

What does the equilibrium line help determine?

A

If a glacier is retreating or advancing downhill, however it is always moving down

34
Q

What is the toe of a glacier?

A

The leading edge of the glacier

35
Q

What happens if the amount of accumulation is equal to the amount of ablation?

A

The glacial toe stays in the same place (glacier gets thicker).

36
Q

What happens if the amount of accumulation > amount of ablation?

A

The glacial toe moves forward.

37
Q

What happens if the amount of accumulation < amount of ablation?

A

The glacial toe retreats upslope and the glacier gets thicker, but it’s still moving down.

38
Q

What force acts on glaciers flowing out over ocean water? What force no longer does?

A

Depositional forces still act in the form of drop stones, but no more erosion force.

39
Q

what are tidewater glaciers?

A

Valley glaciers entering the sea.

40
Q

what are ice shelves?

A

Continental glaciers entering the sea.

41
Q

What is sea ice? What does it require?

A

Non-glacial ice formed of frozen seawater. It requires crystallization.

42
Q

How high above the water does can iceberg have to be to be considered an iceberg?

A

6m

43
Q

Can glaciers change landscapes? How so? (~3 ways)

A

Erosion/transport, and deposition.

44
Q

What is glacial abrasion?

A

A “sandpaper” effect on substrate. Erodes and polishes rough grains.

45
Q

What is substrate?

A

Fine “rock flour”; smallest grain size.

geology (15 decks)

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