Glacial Landforms

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Corrie/Cirque Glacier and Tarn
Snow collects in a hollow. As more snow falls, it compressed and the air is squeezed out
to form neve. The pressure exerted by more layers of snow causes the neve to become
glacier ice. Erosion and weathering by abrasion, plucking and freezethaw action will
increase the size of the hollow.
Even though the ice is trapped in a hollow and unable to move downhill, gravity will still
pull it downwards. This circular motion is known as rotational slip and can cause the ice to
pull away from the back wall creating bergschrund. Plucked debris from the back wall
causes abrasion which deepens the corrie. Some of this debris is deposited at the edge of
the corrie, building up the lip.
When ice in a corrie melts, a circular lake is often formed at the bottom of the hollow,
which is known as a tarn.
Arête
An arête is a knifeedge ridge. It is formed when two neighbouring corries run back to
back. As each glacier erodes either side of the ridge, the edge becomes steeper and the
ridge becomes narrower.
Pyramidal Peak
A pyramidal peak is formed where three or more corries and arêtes meet. The glaciers
have carved away at the top of a mountain, creating a sharply pointed summit.

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Rock Step
As mountain glaciers flow down valley they encounter exposed bed rock of varying
resistance to erosion. The glacier will erode down into weaker rock but have to flow over
the stronger rock. This creates a series of rock steps.
UShaped Valley (Glacial Trough)
A Ushaped valley is the shape left after a valley has been over deepened by a glacier.…read more

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The valley sides may also have truncated spurs which are the ends of sloping ridges cut
off by the valley glacier which tends to flow straighter than a river.
Hanging Valley
The sides of Ushaped valleys may have hanging valleys which are side valleys that are
left high on the side of a main valley that has been deepened by glaciation. Streams
flowing in a hanging valley may form a waterfall as it flows down the steepened sides.…read more

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Roche Moutonnee are outcrops of resistant bed rock with a gentle abraded slope on what
would have been the upstream side of the ice (stoss slope) and a steep rougher slope on
the downstream side (lee slope).
The smooth upstream slope is probably caused by abrasion as the ice advances over the
rock, and the rough 'tail' is due to the action of plucking where ice has attached to the rock
and literally pulled rock fragments away.…read more

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When a glacier moves across the underlying rock, the process of abrasion wears it away.
It is the fragments of rock held in the ice that do the abrading, scraping across the rock
surface like nails across a wooden desk top. Larger rock fragments leave deep scratch
marks behind them. These scratch marks are straight parallel lines that reveal the direction
of ice movement.
Freshly exposed striations have a preferred orientation of rock grains.…read more

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