GEO 110 Lecture Notes - Lecture 10: Cirque Glacier, Bergschrund, Aretes
14 Jun 2016
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Document Summary
Very sharp ragged ridge and separates into two valleys. Different from cirque glacier because they are often the result of head ward erosion by a cirque glacier. Known as fish bone because at the top of the ridge it is very sharp and there are big grooves on either side of the hill. Two alpine glaciers flowing in the opposite direction may erode both sides of the ridge, forming a sharp narrow rib of rock that is perpendicular to the main ridge. Aretes are knife-shaped ridges like fish bone on the adjacent ridges. Rocks embedded in ice scraps across the bedrock cutting deep parallel groves and scratches called striations. When the glacier ice melts, the scratched bedrock is exposed and the marks show the direction of the ice movement. Groves, striations and chatter marks are used interchangeably. It is a series of insertions caused by abrasive acts of the glacier.
