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Geography A Level Content > Glaciation Pack F > Flashcards

Glaciation Pack F Flashcards

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1
Q

What is a cirque?

A

An arm-chair shaped hollow with a steep back and a rock basin
- Macro scale landform

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2
Q

What makes a hollow deep enough to collect more snow?

A

Nivation enlarges the hollow by a combination of freeze-thaw weathering and meltwater which transports the rock debris away, forming a nivation hollow

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3
Q

Why is freeze-thaw weathering important in the creation of a cirque?

A

Freeze thaw weathering breaks up and loosens the rock so that it can be plucked

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4
Q

Why is plucking important in the creation of a cirque?

A

Rock that has been broken by freeze-thaw weathering is plucked which steepens the back wall

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5
Q

Why is abrasion important in the creation of a cirque?

A

Abrasion by rocks picked up from the plucking deepens the corrie and allows the ice to move in a rotational manner (rotational slip)

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6
Q

Why is there a rock lip and what gets deposited on it?

A
  • Rock lip forms as ice leaves the hollow
  • Deposition of debris before the glacier moves out of the corrie
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7
Q

Why may a tarn form in the cirque?

A

Happens post-glacially when the cirque fills with water

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8
Q

Why are the largest and most frequent locations of cirques north-east facing?

A
  • In the lee of prevailing westerly winds
  • In the shadier sites protected from insolation
  • Westerly winds blow snow into the hollows
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9
Q

What is an example of a cirque in the UK?

A

Easedale Tarn in Cumbria

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10
Q

What is an example of a cirque outside the UK?

A

Hodges Glacier, Georgia

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11
Q

What is an arete and what causes them?

A

A narrow, rocky steep-sided ridge formed from the intersection of two cirque headwalls
- Macro scale landform
- Happens when two cirque headwalls erode backwards towards each other
E.g. Striding Edge, Helvellyn

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12
Q

What is a pyramidal peak and what causes them?

A

A horn with steep sides and several aretes radiating from it
- Macro scale landform
- Steep, pointed peak
- Formed when three or more cirques back onto each other
E.g. The Matterhorn, Alps

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13
Q

What is a glacial trough?

A

A steep sided flat bottomed valley
- Macro scale landform

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14
Q

What is the appearance of a glacial trough?

A
  • Straight
  • Wide base
  • Steep sides
  • Stepped long profile
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15
Q

What causes glacial troughs to develop?

A
  • As a valley glacier ice moves through a mountain valley, it straightens, widens and deepens the valley
  • The valley changes from V-shaped to U-shaped
  • Plucking and abrasion widen and deepen the valley
  • Meltwater carrying sediment erodes the bed/banks (subglacial fluvial erosion when under the glacier)
  • Compressional flow means that the glacier will over-deepen parts of the valley floor which forms rock basins
  • Deeper areas of the U-shaped valley are caused by the confluence of glaciers, less resistant geology or well-jointed rocks
  • After glaciation, the sides of the valley get weathered and mass movement moves rocks to the valley base forming less steep sides with scree slops
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16
Q

What is a hanging valley?

A

A valley found higher up on the sides of a U-shaped valley
- Macro scale landform

17
Q

What causes hanging valley?

A
  • Form on the sides of the main valley
  • Might be river valleys from pre-glacial times that weren’t glaciated or smaller glaciers with less power
  • A small side tributary glacier meets a larger main valley glacier
  • The elevation of the surface ice of both the main glacier and tributary are the same in the glacial phase
  • The rate of erosion beneath the main glacier is much greater so the tributary valley is left hanging far above when the glaciers retreat
18
Q

What is a misfit stream?

A

A stream found in a glacial trough which is too small to have eroded the valley it is in
- Macro scale landform

19
Q

What causes a misfit stream?

A
  • Occur on the flat, wide floor
  • Formed after glaciation
  • Forms in a hollow where a glacier has more deeply eroded less resistant rock
  • Indicates that the valley was created by a glacier and not the river
20
Q

What is a ribbon lake?

A

Long, narrow body of water occupying the base of a U shaped valley
- Macro scale landform

21
Q

What causes a ribbon lake?

A
  • Formed where the glacier eroded soft rock more making parts of the valley deeper
  • Rock basin fillls with water post glacially
22
Q

What is a truncated spur?

A

Cliff-like landform where erosion has cut off the interlocking spur
- Macro scale landform

23
Q

What causes a truncated spur?

A
  • Original interlocking spurs were cut away by glacial erosion
  • Any land in the way of a moving glacier will be eroded
  • Due to the inflexibility of glaciers
24
Q

What is an example of a glacial trough?

A

Yosemite Valley, California

25
Q

What is a roche moutonnee?

A

A mass of resistant rock with a smooth, rounded up-valley slope and a steep, jagged down valley slop
- Meso scale landform

26
Q

How is a roche moutonnee formed?

A
  • Formed from a mass of resistant rock on the valley floor
  • Abrasion smooths the stoss (up glacier) side
  • The pressure melting point is reached as the ice moves over the bedrock knoll
  • Meltwater enters joints which leads to freeze thaw weathering when the ice refreezes as pressure decreases
  • Plucking makes the lee (down glacier) side ragged and rough
  • Produces an asymmetric landform that was formed sub-glacially
27
Q

What is an example of a roche moutonnee?

A

Mount Iron, New Zealand

28
Q

What are striations?

A

A series of parallel scratches and grooves in rock showing the direction of ice flow
- Micro scale landform

29
Q

How do striations occur?

A
  • Glacier moves over an area of exposed rock
  • Larger fragments of angular rock embedded in the glacier ice leave a series of parallel scratches or grooves in the bedrock
  • Caused by abrasion
  • The deepest part of the scratch is at the initial point of impact
30
Q

What are examples of striations?

A

Central Park, New York and Easedale Valley, Lake District

31
Q

What are chattermarks?

A

Irregular chips and fractures in the rock
- Wedge shaped mark
- Chipping of bedrock surface

32
Q

What is a crag and tail?

A

A large mass of resistant rock which protects the lee side from erosion, forming a gently sloping tail of deposited material
- Meso scale landform

33
Q

How is a crag and tail formed?

A
  • Glacier ice is forced to flow around a large resistant rock obstacle
  • The hard rock obstacle protects the less resistant material on the lee side from erosion
  • Results in a steep stoss end and a long, gently sloping lee side
34
Q

What is an example of a crag and tail?

A

Edinburgh Castle and the Royal Mile, Scotland

Geography A Level Content (14 decks)

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