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Explain the formation of a corrie
- Snow gathers in a hollow on a north facing slope
- Glacier moves downhill due to gravity and basal sliding
- Plucking steepens the backwall
- Abrasion deepens the hollow
- Rotational movement leads to rock lip where erosive power is least
- After glaciation an arm chair shaped hollow is left, often with a corrie loch or tarn in the hollow
- Freeze-thaw continues on backwall forming scree
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Explain the formation of an arete
- Aretes are sharp knife edged ridges at the edge of two corries
- The form when two corries erode back to back
- Plucking narrows the distance between the two backwalls
- After glaciation a narrow-knife edged ridge seperates the two corries
- This is known as an arete
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Explain the formation of a pyramidal peak
- Three or more corries erode back to back on the same mountain
- Plucking narrows the distance between the three backwalls
- After glaciation, a pointed, hornshaped peak is left
- Freeze-that continues on its summit
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Explain the formation of a glacial trough
- A glacial trough is a steep sided, flat bottomed (u-shaped) valley carved by ice
- They form when a v-shaped river valley with interlocking spurs is occupied by a glacier
- The glacier moves downhill due to gravity and basal sliding
- Plucking and abrasion deepen, widen and straighten the valley
- After glaciation a steep sided, flat bottomed valley is left.
- The spurs have been truncated
- Often a mis-fit stream or ribbon lake is found on the valley floor
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Explain the formation of a hanging valley
- Large glacier in main valley, smalle glacier in tributary valley
- Both are occupied by a glacier and eroded through plucking and abrasion
- Tributary glacier has less power than main glacier so erodes less. This is known as differential erosionAfter glaciation the tributary valley is left hanging above the floor of a larger glacial trough
- The hanging valley is often accompanied by a waterfall
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Explain the formation of scree
- Steep and bare rock faces with lines of weakness/well-joined carboniferous limestone
- Cold climate where temperatures often fall below freezing point at night
- These two factors allow physical weathering to take place in the form of freeze-thaw action, where water collects in the rock fractures, freezes and expands by about 9% exerting great pressure on even the hardest rock
- repeated freeze-thaw action splits the rock into large sharp fragments which break off and are moved downhill by gravity to accumulate at the base of steep slopes as a scree or talus slope as large heaps of rock debris
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Explain the formation of terminal moraine
- terminal moraine are angular, unsorted rocks and sand deposited by a glacier.
- They form a bulldozed ridge up to 30m high across a valley
- It marks the maximum extent the glacier reached
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Explain the formation of an outwash plain
- This is in front of the terminal moraine
- it is formed when sand and gravel is washed out of the glacier by meltwater (water melting from glacier) and deposited as a large flat area in front of the terminal morraine
- It consists of rounded sand and gravel
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Explain the formation of drumlins
- Drumlims are eggshaped mounds formed when the glacier moulds till beneath it, to form streamlined moulds
- They have a steep, blunt, upstream end(stoss)
- And a gently sloping, pointed downstream end (lee)
- The ice flowed towards lee end (downstream)
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