Corrie
From Wikipedia, the free encyclopedia
- This article is about the geographical feature. For the British television series, see Coronation Street. For other uses, see Corrie (disambiguation).
In geography, a corrie is a terrain feature created by glaciation in high mountains. The word is an anglicisation of the Gaelic word coire meaning hollow. In Wales it is known as a cwm (from Welsh for valley).
The French word cirque is also used to denote a very similar geographical feature, though a difference is described below.
[edit] The formation of a corrie
Corries begin as small hollows on a relatively smooth slope.
Snow accumulates in the north- and east-facing hollows. The snow is compacted into ice as air is compressed out, causing it to move downhill. Freeze-thaw weathering and plucking (created jagged, rough surfaces) create a steep backwall. Rocks carried at the bottom of the ice erode the base of the hollow by abrasion(the sandpaper effect , producing smooth surfaces) to form a rock basin. Since the ice exerts a larger pressure over the deepest part of the hollow, rotational slip movement will occur, creating a more gently sloping rock lip, since the rate of erosion here is decreased. Over time, the height of the lip is increased by the deposition of moraine. The rock lip and moraine act as a dam behind which rain water may accumulate after the Ice Age, creating a corrie lake or tarn.
[edit] Related glacial features
Two corries formed close to each other can erode the separating rock until it forms a knife-edged ridge known as an arête.
When three or more corries are formed around the summit of a mountain, they can form a horn or pyramidal peak. In some cases, this peak will be made accessible by one or more arêtes. The Matterhorn in the European Alps is a fine example.
