Cirque formation is the glacial erosional process that carves an amphitheatre-shaped hollow into a mountainside at the head of a valley, beginning where snow accumulates in a preexisting hollow and compacts into a small cirque glacier. Freeze-thaw weathering on the headwall feeds rock debris into the ice through bergschrund crevasses, and the glacier rotational movement over a rock basin deepens the floor by abrasion and plucking, steepens the headwall, and leaves behind a characteristic bowl with a raised lip once the ice retreats, often occupied afterward by a small tarn lake.
Facts
Process Type TimescaleThousands to tens of thousands of years over the course of a single glaciation. 1 Sources
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