arêtes

Arêtes are narrow, knife-edge ridges formed by glacial erosion in mountainous terrain. The term, borrowed from French, describes the slender crest that separates two or more glacial valleys or cirques.

Formation occurs when ice occupying adjacent cirques or valleys erodes laterally. Through grinding, abrasion, and plucking, the rock between the valleys is removed. With glaciers converging from different directions, continued erosion sharpens the crest into a narrow spine that can be only a few meters wide in places and may extend for many kilometers.

Morphology of arêtes is characterized by steep, near-vertical sides and a narrow, sharp crest. The exact width and steepness vary with rock type and glacier dynamics. Weathering and rockfalls gradually wear the ridge, but its high, exposed position often preserves the knife-edge profile. Arêtes commonly occur in conjunction with other glacial features such as cirques, horns, and cols, reflecting a landscape shaped by repeated glaciation.

In addition to their geomorphic significance, arêtes influence alpine hazards and routes. Snow and ice on arêtes can persist as cornices, and the crest and adjacent faces present exposed terrain with potential crevasses and fall risks for climbers. Their presence marks areas of intense past glaciation and helps define the alpine topography.

Arêtes are typical of high mountain glaciated regions worldwide, with prominent examples found in the European Alps, the Andes, and the Himalayas. They illustrate how glacial processes sculpt sharp, elongated ridges that define the character of rugged alpine landscapes.