cirques

A cirque is a bowl-shaped, amphitheater-like hollow carved into a mountain flank by a glacier. Typically enclosed on three sides by steep headwalls, it opens downvalley where a lip marks the outlet. When filled with meltwater, the basin can host a tarn, a small mountain lake.

Formation and morphology: Cirques form in the head of a valley where snow persists long enough to compress into ice. The glacier erodes by rotational motion, plucking pieces of bedrock and abrading the floor, creating a concave profile with a steep back wall. Frost wedging and freeze-thaw processes contribute to the steep headwall, while abrasion tends to smooth the floor. After the ice thaws, the cirque commonly remains as a hollow; erosion can leave benches, steps, or a series of terraces along the lip.

Hydrology and related features: If meltwater fills the basin, a tarn may develop and often sits behind a dam of morainic debris at the lip. Cirques may host moraines that mark the glacier’s minimum and maximum extents. When several cirques exist in proximity, sharp mountain peaks and horn peaks can form where their walls converge.

Distribution and terminology: Cirques are characteristic of glaciated mountain regions worldwide, including the European Alps, the Himalayas, the Rockies, the Andes, and other high-latitude ranges. In some regions a cirque is called a corrie or a cwmy, especially in Scotland and parts of the British Isles.

Relation to other landforms: Cirques are often precursors to hanging valleys and can contribute to the development of sharp, pyramidal peaks where multiple cirques meet. They provide a record of past glacial activity and landscape evolution.