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Topic 2 - Glaciation > EQ3 (2.7/8/9) > Flashcards

EQ3 (2.7/8/9) Flashcards

1
Q

Give examples of macro scale landforms

A
  • corrie
  • arête
  • pyramidal peak
  • glacial trough
  • truncated spur
  • hanging valley
  • knock and lochan
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2
Q

Give examples of meso scale landforms

A

Ribbon lake
Roche moutonnee
Crag and tail

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3
Q

What are examples of micro scale landforms?

A

Striations/chattermarks

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4
Q

What is a Corrie?

A

Armchair - shaped depression in a mountainside with a steep back wall and a rock lip.

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5
Q

What is an arête?

A

Narrow, knife-edge ridge between two corries

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6
Q

What is a pyramidal peak?

A

A pointed mountain peak, with three or more corries.

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7
Q

What is a glacial trough?

A

A U-shaped valley with steep sides and a wide,flat floor.

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8
Q

What is a truncated spur?

A

A steep rocky valley side where spurs of a river used to interlock before glaciation.

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9
Q

What is a hanging valley?

A

A v or u shaped valley high above the main glacial trough floor, often with a waterfall.

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10
Q

What is a ribbon lake?

A

A long narrow lake along the floor of a glacial trough

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11
Q

What is a Roche mountonnee?

A

A mass bare rock on the valley floor, with a SMOOTH STOSS (UPSIDE) and STEEP JAGGERED LEE (DOWNSIDE)

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12
Q

What is knock and lochan?

A

A lowland area with alternating small rocks (knock) and hollows, containing small lakes (lochan).

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13
Q

What is a crag and tail?

A

A very large mass of hard rock forms a steep stoss with a gently sloping tail of deposited material.

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14
Q

What are striations/chattermarks?

A

Chattermarks are a series of often crescent - shaped gauges shipped out of the bedrock as the glacier drags rock fragments underneath it.

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15
Q

How are corries formed?

A

A rounded hollow is eroded. Plucking and abrasion causes the round nature of the Corrie. The downwards movement of the glacier causes the Corrie lip.

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16
Q

How is an arête formed?

A

Plucking and abrasion on the back wall of two corries, mean they erode backwards, creating a narrow ridge. Freeze-thaw weathering also plays a role.

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17
Q

How are pyramidal peaks formed?

A

3 + corries erode towards eachother. This takes place through plucking, freeze-thaw weathering and abrasion.

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18
Q

How are glacial troughs formed?

A

A u-shaped valley is widened and deepened as a result of powerful plucking and abrasion by a valley glacier.

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19
Q

How are truncated spurs formed?

A

Valley glaciers are less flexible than rivers. Removes the ends of interlocking spurs, by plucking and abrasion.

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20
Q

How are hanging valleys formed?

A

Powerful glacial ice eroded rivers that are high above the main valley floor

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21
Q

How are ribbon lakes formed?

A

Increased plucking and abrasion takes place on the valley floor, as a result of weaker rocks.

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22
Q

How are Roche mountonnees formed?

A

The more resistant rock causes ice movement by rock creep and regelation around it. As ice slides over the rock, it scours and smoothes the stoss, while refreezing on the lee causes plucking.

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23
Q

How are knock and lochans formed?

A

Scouring at the base of a glacier excavates areas of weaker rock, forming hollows that fill with meltwater and precipitation following ice retreat.

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24
Q

How are Crag and Tail formed?

A

A very large mass of hard rock forms a steep stoss with a gently sloping tail of deposited material.

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25
Q

How are striations and chattermarks formed?

A

Abrasion by debris imbedded in the base of the glacier, as it passed over. Can indicate the direction of ice movement.

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26
Q

How does ice move past a Roche mountonnee?

A
  • Ice moves along the stoss side. Resistance caused by outcrop, leads to an increase in pressure, causing melting. This leads to a smooth, abraded stoss.
  • As ice moves past the outcrop, pressure reduces and meltwater refreezes. This causes glacial plucking, and a jagged lee.
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27
Q

Describe how a ice moves past a crag and tail?

A

Ice erodes weaker rocks. When it reachers very resistant rock, it moves around the obstacle. This leaves a deposit of material on the lee side - the tail.

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28
Q

What is scouring?

A

Where ice sheets expand beyond constrains of mountain valleys and erode large areas of lower relief land.

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29
Q

What is supraglacial material?

A

Carried on top of the glacial’s surface

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30
Q

What is englacial material?

A

Carried within the body of the glacier.

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31
Q

What is subglacial material?

A

Moved along the base of the glaciee

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32
Q

What is glacial deposition?

A

Unsorted mixture of material deposited by the glacier - called till

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33
Q

What are two types of till?

A
  • Lodgement till

- Ablation till

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34
Q

What is lodgement till?

A

Till spread onto the valley floor beneath the ice by glaciers.

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35
Q

What is ablation till?

A

Till dropped by the glacier in the ablation zone, as the glacier melts, at the glacier snout.

36
Q

What is equifinality?

A

Multiple theories used to explain one final result

37
Q

What is an example of equifinality?

A

Drumlins

38
Q

What is a theory for the formations of drumlins?

A

The Shaw Theory - meltwater caused flooding, which caused irregularity in the bedrock. This causes the formation drumlins. They are then streamlined by advancing ice.

39
Q

Describe a drumlin

A

Ice travels from the blunt end (stoss end) towards the tapered end (lee end).

40
Q

Describe the topography of drumlins?

A

“Basket of eggs” topography

41
Q

How can corries demonstrate ice movement?

A
  • Corrie orientation can show ice movement, as ice will move from the back wall towards the lip of the Corrie.
  • Till fabric analysis - rock fragments (clasts) are parallel to direction of movement.
42
Q

What is an issue with Corrie orientation?

A

Requires large sample size

43
Q

How can glacial troughs be used to show ice extent?

A

A trim line might be identifiable. Below this line, striations and abrasion are visible on polished surfaces. This indicates the height of the glacier

44
Q

What is an issue with using trim lines to identify ice extent?

A

Shows localised ice extent, however height could vary massively along the glacier. E.g. baltoro glacier - Pakistan - 63km long.

45
Q

How can Roche mountonnees show ice movement?

A

By identifying a smooth stoss and a jagged lee, we are able to identify direction of ice movement, as ice travels from the stoss towards the lee.
- Striations also may indicate direction, as they move parallel to ice flow.

46
Q

How can a crag and tail show ice movement?

A

Ice moves from crag over lee, therefore showing direction.

47
Q

What issues come from using Roche mountonnees and Crag and Tail to identify ice movement?

A
  • Multiple glaciation/Post-glacial weathering makes direction unreliable
  • Human activities - farming, mining, infrastructure (buildings and roads)
48
Q

What is lateral moraine?

A

A ridge of moraine along the edge of the valley floor?

49
Q

How is lateral moraine formed?

A

Exposed rock on the valley side is weathered. These fragments fall down and then carried parallel to ice flow.

50
Q

What is medial moraine?

A

A ridge of moraine down the middle of the valley floor.

51
Q

How is medial moraine formed?

A

When two valleys converge, two lateral moraines combine to form a medial moraine.

52
Q

What is terminal moraine?

A

A ridge of moraine extending across the valley at the furthest point the glacier reached.

53
Q

How is terminal moraine formed?

A

Advancing ice carries moraine forward at deposits it at the point of maximum advance when it retreats.

54
Q

Give examples of erosional landforms

A
  • Corries
  • Glacial troughs
  • Roche mountonnees
  • Crag and tail
55
Q

Give examples of depositions landforms

A
  • Terminal moraine
  • Ground moraine
  • Drumlins
  • Erratics
56
Q

How can ground moraine be used to show ice extent?

A

Till fabric analysis

57
Q

How can ground moraine be used show ice movement?

A

Larger till rock (clasts) point in direction of the ice movement.

58
Q

How does terminal moraine show ice extent?

A

Ridge of moraine showing furthest point glacier reached - therefore showing extent

59
Q

What issues are encountered by using ground moraine/terminal moraine?

A
  • Confused by multiple glaciers, post-glacial weathering and human activty
60
Q

How does drumlins show ice extent?

A

Number of drumlins - large swarm of drumlins = large glaicer

61
Q

How does drumlins show ice movement?

A
  • By identifying CRESTLINE, we are able to identify blunt stoss and tapered lee, showing direction.
  • Rate of movement can also be identified by elongation of drumlins: more elongated = faster the ice movement.
62
Q

What is the problems with using drumlins to establish ice movement and extent?

A

Equifinality - can’t say for definite, therefore hard to use for reconstruction.

63
Q

What is an erratic?

A

A Boulder or rock fragment deposited far from its origin.

64
Q

How can erratics be used to show ice movement?

A

Erratics can be located back to their original location, by identifying their rock type.

65
Q

What issues may be associated with using erratics to identify ice movement?

A

May be modified, multiple glaciations, post-glacial weathering and erosion, as well as human activity.

66
Q

What are the 3 types of kames?

A

Delta kames
Kame terrace
Crevasse kame

67
Q

What are examples of fluvio-glacial landforms?

A
  • Kames:
    Delta kames
    Kame terrace
    Crevasse kame
  • Eskers
  • Outwash plains (sandur)
  • Meltwater channels
68
Q

What is an esker?

A

Long, narrow, sinuous ridge of fluvio-glacial sand and gravel. Carries large amount of rock debris under high hydrostatic pressure. This is deposited during the glacier’s retreat.

69
Q

How can eskers be used to show ice extent?

A

Formed englacially/subglacially, so sand and gravel are often found here, during retreat. You can then track ice margin paths.

70
Q

How can eskers be used to show ice movement?

A

Sand and gravel could indicate the direction in which the glacier travels.

71
Q

What are problems with using eskers as evidence for ice movement and extent?

A

Changed shape, and been eroded by post-glacial rivers.

72
Q

What is a kame delta?

A

Small mound-like hills of material deposited by a lake.

73
Q

What is a kame terrace?

A

Material left from a marginal glacier lake, as a ridge.

74
Q

What is a crevasse kame?

A

Material deposited by surface crevasses, creating small hummocks.

75
Q

How can kames be used to show ice extent?

A

Kame terraces are left as a ridge on the valley side, so can show glacier’s width.

76
Q

How can kames be used to show ice movement?

A

Kame terraces run parallel to ice movement, therefore can assume, the downhill direction would be direction of movement.

77
Q

What is the issue with using kames as evidence for ice movement and extent?

A

Kames only formed at the end of the glacial period. As a result, will only show end of glacial span - NOT TRUE EXTENT.

78
Q

What is an outwash plain?

A

A flat expanse of fluvio-glacial debris in front of the glacier snout, of where meltwater streams lost energy and deposited material.

79
Q

How can outwash plans be used to show ice extent?

A
  • Edge of sandur - edge of glacier.
80
Q

How can outwash plains be used to show movement?

A

Span parallel to ice flow

81
Q

What is the issues with using outwash plains as evidence for ice movement and extent?

A

Multiple glaciation, human activity e.g. farming

82
Q

What are meltwater channels?

A

Narrow channel that can cut into bedrock, due to the high hydrostatic pressure it is under.

83
Q

How can meltwater channels be used to show ice extent?

A
  • Evidence of ice margins.

- Can show glacial retreat

84
Q

How can meltwater channels be used to show ice movement?

A

Usually for, parallel to ice flow.

85
Q

What are the issues with using meltwater channel for evidence for ice movement and extent?

A

Under so much hydrostatic pressure, erosional paths may not have been followed accurately.

86
Q

What is a kettle lake?

A

A circular depression found in the outwash plain, that is filled with meltwater

87
Q

What is a kettle hole?

A

A kettle lake without the meltwater.

A circular depression

Topic 2 - Glaciation (6 decks)

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