Cirque

(geology) A steep elliptic to elongated enclave high on mountains in calcareous districts, usually forming the blunt end of a valley. Also known as corrie; cwm.

A cliffed rock basin, shaped like half a bowl, at the head of a mountain valley. Cirques may be shallow if glacier erosion is slight, but may be 1600–2600 ft (500–800 m) from the top of the headwall to the cirque floor if erosion is deep. Cirques occur in glaciated mountains all over the world. Some cirques used repeatedly by glaciers over long periods of years are excavated profoundly. Many cirques contain small glaciers today that were inherited from a huge cirque cut by glaciers long ago. Well-formed cirques have steep rock walls and floors that slope down-valley or back toward the base of the headwall. Some cirques are cup-shaped rock basins holding rainwater; a lake formed in them is a tarn. If glacial deposits, such as till or a small moraine on the cirque floor, form a depression for a lake the lake is known as a moraine-dammed lake.