Geography-Lithosphere-Glacial erosion and deposition

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Smyth159
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77577
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Geography-Lithosphere-Glacial erosion and deposition
Updated:
2011-04-05 13:47:43
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Geography Lithosphere Glacial erosion deposition
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Geography-Lithosphere-Glacial erosion and deposition
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  1. 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
  2. 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
  3. 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
  4. 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
  5. 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 erosion
    • After glaciation the tributary valley is left hanging above the floor of a larger glacial trough
    • The hanging valley is often accompanied by a waterfall
  6. 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
  7. 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
  8. 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
  9. 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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