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| Landforms of Glacial Erosion | ||
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The
photo shows a cwm on Cader Idris this is Cwm Cau and its corrie lake or
tarn called Llyn Cau.
A corrie (also called a cirque or cwm) starts as a snow patch on a cold mountain side. The temperatures must be low enough to allow the snow to remain all year round. Under these conditions snow can accumulate and the snow patch will grow in size and depth each year. Due to temperature changes and pressure, the snow becomes altered to ice, and when sufficient ice has accumulated it will begin to move downhill under the influence of gravity. |
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| This arete was shaped as two glaciers eroded away at opposite sides of Mount Oberlin. One glacier flowed along the current Logan Creek, and the other glacier flowed north along the unnamed stream where the waterfall is. Mt. Oberlin (se arrow) in Glacier National Park (Canada) is an example of an arete. |  |
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On the map, the arete is shown by elongate closed contour lines, and the close spacing of these contour lines reveals the steep sides of the arete. The camera on the map shows the pont the photo was taken from. | |
| When three or more corries erode backwards and meet they cannot form an arete; it has steep sides but doesn't have the length to make a ridge. Imagine three corries at the corners of a triangle, eventually all eroding back and meeting in the middle. A sharp pointed pyramid shape is created. This is called a Pyramidal Peak, or Horn, and is a common shape for mountain tops in well glaciated areas. The photo shows The Matterhorn from Switzerland. |  |
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