Cirque

A cirque is an amphitheater-like valley formed by glacial erosion. Alternative names for this landform are corrie and cwm. A cirque may also be a similarly shaped landform arising from fluvial erosion.

The concave shape of a glacial cirque is open on the downhill side, while the cupped section is generally steep. Cliff-like slopes, down which ice and glaciated debris combine and converge, form the three or more higher sides. The floor of the cirque ends up bowl-shaped, as it is the complex convergence zone of combining ice flows from multiple directions and their accompanying rock burdens. Hence, it experiences somewhat greater erosion forces and is most often over deepened below the level of the cirque's low-side outlet and its down-slope (backstage) valley. If the cirque is subject to seasonal melting, the floor of the cirque most often forms a tarn (small lake) behind a dam, which marks the downstream limit of the glacial over deepening. The dam itself can be composed of the moraine, glacial till, or a lip of the underlying bedrock.