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A level Geography - Physical > Glaciers - Erosion + Deposition > Flashcards

Glaciers - Erosion + Deposition Flashcards

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1
Q

What is the difference between weathering and erosion

A

Erosion = the wearing away and removal of rock material by a MOVING force (moving ice)

Weathering = the breakdown and decay of rock in situ woth NO MOVEMENT or removal involved

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2
Q

Give two processes of glacial erosion

A

Plucking (also known as Quarrying)

Abrasion

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3
Q

What is plucking

A
  • Meltwater seeps into joints in the rocks of the valley floor and sides
  • This water then freezes and becomes attached to the glacier
  • As the glacier advances, it pulls pieces of rock away
  • Plucking is particularly effective under temperate glaciers where basal ice is at the pressure melting point and when the bedrock is highly jointed
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4
Q

What is abrasion (in relation to glaciation)

A

1) Debris entrained in the ice at the base and sides of the glacier rubs against surface rocks, wearing them away like sandpaper

2) Abrasion can have two effects depending on the nature of the debris in the ice:
- Coarse and angular debris scrapes and scratches rock to form striations which are long and thin grooves in the bedrock
- Finer debris is polished and smoothes the bedrock

3) Very fine material is produced by abrasion called rock flour. This is washed out in meltwater streams making the water a milky colour

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5
Q

Give 3 processes of weathering in glacial environments

A

Freeze-thaw (frost shattering)

Dilation

Nivation

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6
Q

Describe freeze-thaw weathering

A

1) Water seeps into cracks and joints in the rock
2) when it freezes it expands by 9-10% in volume
3) Water in the cracks melts when the temperature rises above 0ºC and is common between day and night
4) This process is most active on the valley sides and the mountains surrounding the glaciers above the ice, but less so under the glacier where the temperature is more constant

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7
Q

What is Dilation (pressure release weathering)

A

1) Glaciers exert considerable downward pressure on the bedrock bellow
2) When a glacier retreats or the ice thickness is reduced, the pressure is reduced
3) The rock on the valley floor, and to a lesser extent the sides, expand and fracture as the weight is removed
4) This makes the rock fracture in layers parallel to the surface

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8
Q

What is nivation

A

1) Snow patches often form in hollows on north-facing slopes
2) In the summer, as the snow patches melt, some of the meltwater percolates into cracks in the rock below the snow patch which then leads to freeze-thaw weathering
3) When there is intense melting, meltwater streams transport the weathered material from bellow the snow patch
4) A process is known as solidification also transports weathering material downslope by the force of gravity
5) This series of processes are responsible for enlarging small hollows which can then form cirques or corries

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9
Q

What is a corrie/cirque

A

Oval-circle shaped valley which is formed through erosion of ice or glaciers

Formed through nitration - Mt Blanc

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10
Q

What is an arête

A

An enlarged ridge - formed when neighbouring corries run back to back as each glacier erodes the other side of the ridge - edge becomes steeper and narrower

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11
Q

What is a pyramidal peak

A

Angular, sharpy pointed mountain peak

Formed by glaciation

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12
Q

What is a glacial trough

A

U shape, a steep-sided, broadly flat bottomed valley formed by the erosional process of a glacier

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13
Q

What is a truncated spur

A

Steep cliffs in a glacial trough

Caused when a glacier has cut-off the tips of rocky spurs as it moves downhill

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14
Q

What is a hanging valley

A

A small valley hanging above the main valley

Formed when small tributary glacier has not been able to erode down as the large glacier is present

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15
Q

What is a Roche moutonnee

A

A bare outcrop of rock on the valley floor that has been sculpted by lots of ice

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16
Q

What are the different sources of debris transported by a glacier

A

Nivation
Avalanche
Erosion - plucking + abrasion
Scree - freeze-thaw weathering

17
Q

What is drift

A

All the material deposited during glaciation

18
Q

What is till

A

Material deposited directly by glacial ice

19
Q

What is outwash

A

Material deposited by meltwater

20
Q

30% of Europe is covered by………mainly deposited in past glacial periods

A

drift

21
Q

What are the characteristics of till

A

Jagged and angular - due to less erosion, particularly by meltwater and attrition

Unsorted because glaciers do not deposit particles on order of size

Unstratified as glacial till is dropped in mounds and ridges, not in layers

The orientation of the long axis is parallel with the direction of ice flow, offers less resistance to the ice

22
Q

What is Till Fabric Analysis

A

Fieldwork technique to determine the orientation and shape of deposits

23
Q

What factors affect rates in erosion, transportation and deposition of glaciers

A 
Discharge in meltwater streams 
Warm based glacier 
Gradient 
Type of sediment, large rock = erode more 
Less accumulation = less erosion
24
Q

What is Laminar flow

A

Movement of individual layers within the glacier, often the layers on the annual accumulation

25
Q

What is Intergranular

A

When individual ice crystals re-orientate in relation to each other

26
Q

What is basal sliding

A

Ice slides over the valley floor because meltwater has reduced friction between the base of the glacier and the valley floor. Friction can lead to the formation of meltwater

27
Q

Give 3 basal movements

A

Sliding
Creep
Sub-glacial deformation

28
Q

What is basal creep

A

Occurs as ice deforms under pressure when encountering obstructions on the valley floor. This enables the ice to spread around and over the obstruction, before re-freezing again when the pressure is reduced

29
Q

WHat is sub-glacial deformation

A

When ice is carried by saturated base sediments moving beneath it on gentle gradients

30
Q

What is extending

A

Ice moving over a steep slope is unable to deform quickly enough and so it fractures, forming crevaces.

31
Q

What is compression

A

When the gradient is reduced, the ice thickens and the following ice pushes the slower moving, leading ice

A level Geography - Physical (19 decks)

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