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Geology > Dynamic Surface L12 > Flashcards

Dynamic Surface L12 Flashcards

1
Q

What is the snowline?

A

The lower topographic limit of permanent ice and snow

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2
Q

What is the main effect on snowline?

A

Latitude

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3
Q

What is snow’s crystal structure?

A

Hexagonal

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4
Q

What is ice’s crystal structure?

A

Cubic

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5
Q

What is glacier ice’s crystal system?

A

Hexagonal

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6
Q

What is frazil ice?

A

Ice that forms in supercooled turbulent water

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7
Q

At what temperature does frazil turn into sea ice?

A

-1.8C

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8
Q

What is pack ice?

A

Consolidated sea ice

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9
Q

How do icebergs affect sedimentation?

A

Icebergs contain sediment from the continent and float considerable distances away from their source depositing sediment when they melt.

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10
Q

Describe the crystal structure of ice.

A

H2O molecules are arranged in tetrahedral patterns that form hexagonal rings of oxygen atoms. A single crystal of ice consists of stacked layers of these rings.

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11
Q

What is the basal plane?

A

The plane of hexagonal rings in ice

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12
Q

What is the c-axis of ice?

A

The direction of stacking of the layers of hexagonal rings in ice

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13
Q

What is polycrystalline ice?

A

Ice that contains many grains with different orientations of their c-axes.

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14
Q

What determines the fabric of ice?

A

The way in which the c-axes are orientated relative to each other

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15
Q

What is basal glide?

A

The deformation of a single crystal when shear stress is applied along its basal plane

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16
Q

What does the pressure on ice needed for it to flow depend on?

A

Gradient

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17
Q

How does cold dry ice flow?

A

By internal deformation

18
Q

How does meltwater and wet sediment help ice to flow?

A

By acting as lubricants between the ice and the bedrock

19
Q

What are the 4 types of glacial environments?

A

Ice sheets
Valley glaciers
Tidewater glaciers
Piedmont glaciers

20
Q

What is a tidewater glacier?

A

Where a glacier meets the sea

21
Q

What is a piedmont glacier?

A

A glacier that is found at the foot of a mountain and forms from the amalgamation of several valley glaciers

22
Q

What is the ablation zone?

A

The zone along a glacier in which ice loss is greater than ice gain

23
Q

What is the accumulation zone?

A

The zone along a glacier in which ice gain is greater than ice loss

24
Q

When does a glacier retreat?

A

When ablation > accumulation

25
Q

When does a glacier advance?

A

When accumulation > ablation

26
Q

How does a temperate glacier flow?

A

Ice moves over the bedrock

27
Q

How does a polythermal glacier move?

A

Ice moves by internal shearing but over the bedrock during glacial surges

28
Q

What is a moraine?

A

Piles of disturbed unsorted material at the sides or front of the glacier

29
Q

Is moraine well or poorly sorted?

A

Poorly sorted

30
Q

What is a drumlin?

A

Oval shaped hill composed of ground moraine that form below the glacier in the direction of ice flow

31
Q

What is terminal moraine?

A

Sediment that has been deposited at the nose of the glacier at its maximum extent

32
Q

What is a kettle hole?

A

Ice dropped off at the nose of the glacier into the moraine eventually melts leaving behind a pond of melt water

33
Q

What is an esker?

A

A sinuous deposit of sorted sediment that forms when subglacial streams drop their sediment.

34
Q

What is a lateral margin stream?

A

Streams of water that flow between the valley side and the glacier that often deposit sediment forming kame terraces.

35
Q

What is a kame terrace?

A

Sediment deposited by lateral margin streams at the sides of the glacier.

36
Q

What is a sandur?

A

An outwash plain formed by glacial meltwaters

37
Q

What are some features of sandurs in the geological record?

A

Sandstone dykes
Frozen sand clasts

38
Q

What are glacial dropstones?

A

Large pieces of sediment that have been carried out to sea by icebergs and dropped to the sea floor during melting

39
Q

What are glacial varves?

A

A very thin annual layer of sediment deposited during cycles of melting

40
Q

What is isostatic rebound?

A

The rising of the lithosphere which has previously been depressed by the weight of glacial ice

Geology (17 decks)

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