Higher Geography > Glaciation > Flashcards

Glaciation Flashcards

(51 cards)

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1
Q

Interglacial period

A

Warmer period

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2
Q

Glacial period

A

Extreme Arctic cold

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3
Q

How long does the glacial and interglacial period last for on average?

A

Glacial - 100,000 years

Interglacial - 10,000 years

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4
Q

Freeze thaw weathering

A
  1. Water enters cracks during the day
  2. Water freezes, expands by 10% and levers rock apart
  3. Pieces of rock break off and fall into glacier below
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5
Q

Formation of glacial ice

A
  1. Snow falls and accumulates. Snow has an ice crystal lattice structure and spaces mainly filled with air give a fluffy texture
  2. Snow melts slowly (ablation). Meltwater seeps downwards and refreshes at deeper level. Snow compacts due to crystals collapsing and expelling air. Now névé layer (granular)
  3. Névé that lasts a full season and becomes buried beneath the new seasons snowpack is called firn. Firn is found below the level where ablation occurs in névé. With additional weight from above because added snowfall, firn gets more compacted. Becomes denser.
  4. Increasing compression causes snow/névé/ firn crystals to metamorphose under pressure until they’re squeezed into a solid.
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6
Q

Basal slip

A

Meltwater lubricates base to allow glacier to slide downhill

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7
Q

Plucking

A

Action of ripping/pulling and detaching rocks from the underlying rock and becomes embedded into the ice as it moves onwards. This erodes the valley base and sides and provides rock debris material.

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8
Q

Abrasion

A

The rock debris embedded in or being moved along with the base and sides of the glacier scours, scrapes and grinds against the valley sides and floor. Wears away and smooths the underlying rock.

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9
Q

Internal deformation

A

Created because of the weight and pressure of the ice which causes the ice crystals to distort and realign in the direction of the movement of ice. Allows ice crystals to slide past each other and the glacier to move downhill.

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10
Q

Example of a Corrie

A

Loch Nagar

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11
Q

What is a bergschrund

A

A crevasse that forms where the moving glacier ice separates from the stagnant ice or firn above.
Example - Ötztal Alps

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12
Q

How is a Corrie formed

A
  1. Snow accumulates in north facing mountain hollows, where there’s more shade.
  2. Snow builds and compacts into ice (névé). During a thaw, water penetrates cracks in base rocks of hollows. FTA breaks more rock. Meltwater removes disintegrated material and hollow largens. Steep back wall is formed. Plucking.
  3. Action of gravity means ice moves downhill. Pressure from inputs cause RTS.
  4. Stones frozen in base grind or abrade base, deepening it. Glacier retreats and melts. Can leave tarn/ lake.
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13
Q

How is an arête formed?

A

formation of corrie

Two from back to back

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14
Q

How is a pyramidal peak formed?

A

Formation of corrie

Three or more form back to back

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15
Q

Example of an arête

A

Striding edge, Lake District

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16
Q

Example of a pyramidal peak

A

Hellvellyn, Lake District

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17
Q

How is a U shaped valley formed?

A

Formed by the process of glaciation. It has the characteristics of a U shape - steep sides and flat bottom. It occurs when a glacier widens and over steepens a V shaped stream valley.
As a glacier moves downhill through the valley, the shape transforms by plucking and abrasion. Results in large rocky material (glacial till) being carried in the glacier. Boulder clay is deposited on the floor of the valley. As the ice melts and retreats the valley is left with very steep sides and a wide flat floor.

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18
Q

What is a ribbon loch? Give an example.

A

A flooded U shaped valley. Form after glaciation where deep gouges in the U shape valley are filled with glacial meltwater. The gouges are a result of over deepening by abrasion due to a number of factors - rotational sliding by the glacier, the action of a tributary glacier, exposure of fault lines/lines of weakness.
Example - Loch Morar

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19
Q

What is a hanging valley?

A

A hanging valley is a smaller side valley left ‘hanging’ above the main U shaped valley. A waterfall can often be seen. During glaciation, the smaller side valley contains less ice than the main glacial valley, which is why it is not as deeply eroded. This is called differential erosion.

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20
Q

Example of a hanging valley

A

Glen Nevis

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21
Q

Example of a mis fit river

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A

Bealach na ba, Applecross

22
Q

What is a crag and tail?

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A

A tadpole shaped landform developed by glacial erosion of rocks of unequal resistance. The crags are cliffs developed in near cylindrical masses of strong rock. The tail is formed in softer rocks sheltered from erosion in its lee.

23
Q

What is a roches mountonnées?

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A

A Roche mountonnée is a rock hill shaped by the passage of ice to give a smooth up side and a rough plucked and cliff like surface on the down ice side.

24
Q

Example of a Roche mountonnée

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A

Central Park, New York

25
What are the six main types of moraine
1. Supraglacial moraine 2. Subglacial moraine 3. Englacial moraine 4. Lateral moraine 5. Medial moraine 6. Terminal moraine
26
What is subglacial moraine
Found anywhere on the surface of the glacier. Can describe lateral and medial moraine that has not reached beneath surface of ice, moraine which falls from the valleys idea to cover areas of the surface as well as any rock debris or dust that settles on the top of the glacier.
27
What is subglacial moraine
Debris that is carried along the valley floor by moving ice
28
What is englacial moraine
Refers to any material that is found trapped within the body of the ice
29
What is lateral moraine
Forms along the sides of the glacier and consists of plucked material and which has fallen from the valley sides.
30
What is medial moraine
Where two glaciers merge a medial moraine is formed where two of their lateral moraines have joined together.
31
What is terminal moraine
Marks the end points of the glacier at its furthest extent
32
What are the two types of glacial deposition
Fluvioglacial - impacted on by water off the glacier. | Subglacial - deposited by the ice itself.
33
Name four fluvioglacial landforms of glacial deposition
1. Kettle holes 2. Eskers 3. Out wash plains 4. Kane terraces
34
Name six subglacial landforms of glacial deposition
1. Drumlins 2. Erratics 3. Medial moraine 4. Lateral moraine 5. Terminal moraine 6. Hummocky moraine
35
What is a drumlin
Drumlins are formed from thick till, often around a rock core. Often found in swarms. They run parallel to the direction of ice, stops end first.
36
How is a drumlin formed
1. Fluvioglacial deposition beneath ice 2. Fluvioglacial deposition then compressed, deposited upon and re shaped by moving ice. 3. Changes in pressure and movement within ice results in wave motion of basal ice and deposition of drumlins during the upwards movement smoothing of deposits as ice moves downwards. 4. Bedrock deflection of basal flow creating an upward followed by downward ice movement and deposition around core of rock.
37
Example of drumlins
Valley of a hundred hills, Torridon
38
What is an erratic
Glacially transported blooms or rock deposited directly by the ice. Too big to be carried by water
39
Example of an erratic
Knoydart, Scotland
40
How is an out wash plain formed
Tributary rivers join together and join trunk of river. Material called delta is deposited at the end of the river. The river is blocked by the channel depositing material so it has to find a new journey and so the rivers braid.
41
Example of outwash plain
Alaska
42
What is a kettle hole
Kettle lochs are depressions which fill with water as ice left by retreating glacier melts.
43
How is a kettle hole formed
They're created by blocks of ice calving off the front of the glacier. Sands and gravels are washed around them, and sometimes cover them. After the ice has melted, they are left with depressions in the ground and may fill with water.
44
Example of a kettle hole
Loch Kinord
45
What is an esker and example
Long snake like ridges running parallel to the valley they're in. Loch Kinord
46
How is an esker formed
Formed from stratified sand and gravel carried in glacial meltwater. River flowing within the glacier may become blocked with moraine. After the river retreats the material is deposited along the valley floor.
47
What is a kame terrace
Kame is material deposited in layers to form small hills. The hills tend to have flat, plateau like surfaces. Alternate layers of sand and grave, are laid down in meltwater lochs or in ice crevaces or in meltwater channels running along the edges of the glacier. Fluvioglacial
48
How is a kame terrace formed
They're formed by material being deposited in glacial lakes or streams that run between the ice and the valley sides. The heaviest material is deposited first so they have gravel at the bottom and slit and clay nearest to the top.
49
What are the inputs into the glacial system
Precipitation, avalanches, snowfall, sublimation
50
What are the outputs out of the glacial system
Evaporation, basal slippage
51
Name the different ice masses
Ice sheet and ice caps - slow moving, continuous sheets/layers of ice - cover extensive areas Mountain/ valley glaciers - Held within valley - directs movement of ice Piedmont glaciers and ice shelves - Glaciers which upon reaching the foot of glacier region are spread out onto flat ground
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