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AS Geography > Glacier Systems and Processes > Flashcards

Glacier Systems and Processes Flashcards

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1
Q

What type of system is a glacier?

A

Open system.

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2
Q

How are glaciers formed?

A

Thin, granular snow called névé (or firn) compacts to form a large mass of ice.

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3
Q

What is the glacial budget?

A

The difference between annual accumulation and ablation (mass balance).

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4
Q

What are the three states of budget (mass balance) within a glacier?

A
  • Positive
  • Neutral
  • Negative
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5
Q

What is the equilibrium line?

A

The boundary between the zone of accumulation and the zone of ablation.

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6
Q

What is the snow line?

A

The boundary between snow-covered areas and areas with no snow cover.

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7
Q

What is accumulation?

A

The addition of mass to a glacier.

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8
Q

What is ablation?

A

The loss of mass from a glacier.

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9
Q

What are the two types of glaciers?

A
  • Cold-based (polar)
  • Warm-based (temperate)
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10
Q

What are the main features of a cold-based glacier?

A
  • Large area
  • Low precipitation and melting
  • Internal deformation
  • Glacier frozen onto bedrock
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11
Q

What are the main features of a warm-based glacier?

A
  • Small area
  • High precipitation and melting
  • Internal deformation and basal sliding
  • High levels of erosion and deposition
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12
Q

Why is subglacial meltwater present within warm-based glaciers?

A

Basal temperatures are at or above the PMP.

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13
Q

What is the PMP?

A

Pressure melting point
- The temperature at which ice melts under pressure.

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14
Q

What are the two types of weathering in cold environments?

A
  • Frost action
  • Nivation
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15
Q

What is frost action?

A

Water enters cracks in rocks during the day and freezes overnight, before expanding by 9% which exerts pressure and causes rock fragments to break off.

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16
Q

What is nivation?

A

A common process in periglacial environments where the alternating freezing and thawing of snow and ice causes erosion beneath patches of snow.

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17
Q

What are the five types of ice movement in cold environments?

A
  • Internal deformation
  • Basal sliding
  • Compressional flow
  • Extensional flow
  • Rotational slip
18
Q

What is internal deformation?

A

The pressure exerted by a glacier causes ice crystals to align and slide over one another, causing ice movement.

19
Q

What is basal sliding?

A

The lubrication provided by subglacial meltwater causes ice movement.

20
Q

What is compressional flow?

A

A glacier will slow down, compress and thicken when it reaches a shallower gradient.

21
Q

What is extensional flow?

A

A glacier will speed up, extend and become thinner when it reaches a steeper gradient.

22
Q

What is rotational slip?

A

Compressed ice within a hollow/depression rotates and causes erosion due to gravity and meltwater.

23
Q

What are the 2 types of erosion in cold environments?

A
  • Plucking
  • Abrasion
24
Q

What is plucking?

A

A glacier becomes frozen on to rock outcrops and pulls away pieces of rock as it moves.

25
Q

What is abrasion?

A

Rocks within a glacier scrape the valley sides and floor, leaving behind striations.

26
Q

When does deposition occur?

A
  • Ice melting at the glacial snout
  • During the change between compressional and extensional flow
27
Q

What are the characteristics of glacial deposits?

A
  • Unstratified
  • Unsorted
  • Angular
28
Q

What are the characteristics of fluvioglacial deposits?

A
  • Stratified
  • Sorted
  • Smooth/rounded
29
Q

What are the characteristics of meltwater channels?

A
  • High discharge
  • Turbulent flow
  • High erosive power
30
Q

What is permafrost?

A

Ground that is permanently frozen below 0°C for more than two consecutive years.

31
Q

What are the three categories of permafrost?

A
  • Continuous
  • Discontinuous
  • Sporadic
32
Q

What is the active layer?

A

The thin top soil layer of permafrost which thaws in summer and causes waterlogging.

33
Q

What are the three types of periglacial mass movement?

A
  • Solifluction
  • Scree
  • Frost heave
34
Q

What is solifluction?

A

The slow downslope movement of soil particles as they become saturated due to waterlogged soils in summer months.

35
Q

Why does the active layer become waterlogged?

A

The permafrost below is impermeable and rainwater/meltwater cannot percolate through it.

36
Q

What is scree?

A

Scree gathers at the base of steep cliffs/slopes due to freeze-thaw weathering.

37
Q

What is frost heave?

A

Anomalous expansion of water to ice crystals in the active layer causes the upward expansion of the soil surface.

38
Q

What is the difference between lodgement till and ablation till?

A

Lodgement till is deposited underneath the ice, whereas ablation till is deposited by melting ice.

39
Q

Where are subglacial meltwater channels present?

A

Between the base of the ice and the bedrock.

40
Q

Where are englacial meltwater channels present?

A

Confined in tunnels within the ice.

41
Q

Where are supraglacial meltwater channels present?

A

On the surface of the ice in meltwater channels.

42
Q

What is the difference between the grading of glacial and fluvioglacial sediments?

A

Glacial sediments are poorly graded, whereas fluvioglacial sediments are well-graded (larger material is deposited first).

AS Geography (29 decks)

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