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Glaciated uplands: processes and landforms
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Ice sheets covered much of the UK in the last ice age. The landscapes they carved are still clear in Scotland, Wales and the Lake District.
Glacial processes
Plucking: meltwater freezes onto rock, and as the glacier moves it pulls pieces away.
Abrasion: rocks frozen into the base of the ice scrape the valley floor like sandpaper.
Glaciers transport material on, within and beneath the ice, and deposit it as moraine (unsorted till) when the ice melts.
Today, on these relict landscapes, freeze-thaw weathering and mass movement (rock falls, slides, soil creep) still change the slopes.
Abrasion: rocks frozen into the base of the ice scrape the valley floor like sandpaper.
Glaciers transport material on, within and beneath the ice, and deposit it as moraine (unsorted till) when the ice melts.
Today, on these relict landscapes, freeze-thaw weathering and mass movement (rock falls, slides, soil creep) still change the slopes.
Erosional landforms
Corrie: an armchair-shaped hollow where a glacier began; it may hold a small lake, a tarn.
Arete: a knife-edge ridge between two corries.
Glacial trough: a steep-sided, flat-floored U-shaped valley; it may contain a long ribbon lake.
Truncated spurs are spurs cut off by the glacier; hanging valleys are side valleys left high above the trough, often with waterfalls.
Roche moutonnee: a rock with a smooth upstream side (abrasion) and a steep, jagged downstream side (plucking).
Arete: a knife-edge ridge between two corries.
Glacial trough: a steep-sided, flat-floored U-shaped valley; it may contain a long ribbon lake.
Truncated spurs are spurs cut off by the glacier; hanging valleys are side valleys left high above the trough, often with waterfalls.
Roche moutonnee: a rock with a smooth upstream side (abrasion) and a steep, jagged downstream side (plucking).
Depositional landforms
Ground moraine: a sheet of till left on the valley floor.
Terminal moraine: a ridge of till across the valley marking the furthest point the ice reached.
Drumlins: egg-shaped hills of till, with the blunt end facing up-glacier.
Crag and tail: a hard rock crag that protected a gentle 'tail' of softer material behind it, such as Castle Rock and the Royal Mile in Edinburgh.
Terminal moraine: a ridge of till across the valley marking the furthest point the ice reached.
Drumlins: egg-shaped hills of till, with the blunt end facing up-glacier.
Crag and tail: a hard rock crag that protected a gentle 'tail' of softer material behind it, such as Castle Rock and the Royal Mile in Edinburgh.
Explain how a corrie forms.
- Snow collects in a hollow on a shaded mountainside and turns to ice.
- Plucking steepens the back wall and abrasion deepens the floor.
- Freeze-thaw weathering supplies more rock.
- When the ice melts, a lip of rock or moraine may trap a tarn.
Answer: A hollow is deepened by abrasion and steepened by plucking; a tarn may form when the ice melts.
Glaciers erode by plucking and abrasion and deposit unsorted till as moraine. Erosional landforms: corries, aretes, U-shaped troughs, truncated spurs, hanging valleys, roche moutonnees. Depositional: ground and terminal moraine, drumlins, crag and tail.
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