Aretes

An arete, plural arêtes, is a narrow, knife-edged crest that separates two adjacent glacial valleys or cirques. The term comes from the French arête, meaning edge or ridge. In glacial geomorphology, arêtes form when alpine glaciers erode the sides of a mountain ridge from opposite sides. As glaciers widen their valleys, the ridge between them is narrowed and sharpened. If several cirques erode a peak from multiple directions, a horn forms, whereas when two cirques erode opposite sides, a razor-like arête remains between them.

Morphology and formation are closely linked to glaciation. An arête typically has steep, exposed flanks on either side and a narrow crest that can be weathered and fractured by frost action. They may persist as prominent features for long distances, often extending across hundreds of meters or more in length, while the crest itself can be only a few meters wide in places. Erosion and rockfall continually modify arêtes, sometimes creating serrated profiles.

Arêtes are characteristic of high mountain regions with a history of glaciation. They occur in mountain ranges worldwide, including the Alps, Himalayas, Andes, and Rockies. In terrain, they are often part of a system that includes cirques, horns, cols, and passes. In addition to their geomorphic significance, arêtes can pose hazards to climbers and influence local microclimates and hydrology through their role in directing meltwater runoff.