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Contents 1 Glacial Erosion 1.1 U-shaped valleys 1.2 Corries 1.3 Arete

Glacial Erosion

(currently lacking diagrams)

U-shaped valleys

A mountain area prior to glaciation. Narrow V-shaped valley with interlocking spurs. River erosion prominent.

Temperatures cool, snow accumulates in hollows on mountainside, compacting to ice under its own weight. Ice flows downhill; following the river valley, eroding it, widening and deepening it. Erosion is by plucking (sapping) and by abrasion (scouring). Frost shattering may occur on bare rock slopes above the glacier. Moraine (rocks, stones, boulders etc.) carried in the ice.

Over deepened glacial valley. U-shaped, steep sided and flat floored. Truncated spurs along valley sides where the ends of the interlocking spurs have been eroded away. Misfit stream because the river is much smaller than it should be for a valley of this size. Moraine may be deposited on valley floor.

Corries

Temperatures drop, more snow accumulates in winter than melts in summer. Especially in N and NE facing hollows Snow compacts into ice under its own weight.

Ice flows downhill out of the corrie, feeding the valley glacier. Ice moves in the corrie with a rotational movement, deepening the corrie and steepening the back and side walls. Frost shattered rocks fall onto the glaciers and into bergshrunds and will be used in the erosive process. Mainly plucking on the back wall and abrasion in the hollow.

On melting of the ice - deep arm-chair-like hollows left. Steep back and side walls. Often over deepened with a higher sill. The sill holds back a lochan. Often scree slopes are present.

Arete

Hollows existing side by side and filled with snow. Compacts into ice and flows downhill.

The ice in hollow moves with a rotational movement, deepening the hollow to form a corrie (by abrasion) and eroding into the headwall by plucking. The intervening high ground between the two corries is eroded and narrowed.

Continued erosion may reduce this intervening ground to a knife edge ridge.