crevasse

A crevasse is a deep fracture in a glacier or ice sheet that forms in the brittle surface ice as it deforms under stress. Crevasses result primarily from tensile stresses generated when ice moves at different speeds or encounters changes in bed topography, slope, or width. They commonly develop where glacier ice accelerates, bends, or flows around obstacles, and their appearance can indicate local flow conditions.

Crevasses vary in size and shape. Transverse crevasses cut across the direction of flow, while longitudinal crevasses run roughly parallel to flow. Open crevasses expose the underlying ice, often with snow bridges over their crests; bergschrund is a specific type at the head of a glacier where moving ice separates from an overlying snowfield. Some crevasses may be temporarily closed by snow or ice bridges, making them dangerous and partially hidden.

Hazards and safety: Crevasses pose serious risk to mountaineers and climbers; snow bridges can collapse without warning. Safety practices include roping teams, probing suspected bridges, and avoiding crossings over uncertain sections. Awareness of weather conditions and visibility is important, as these factors affect the ability to detect cracks.

Impact and monitoring: Crevasse patterns reveal aspects of glacier dynamics and flow rates. Glaciologists map and monitor crevasses using ground surveys, aerial photography, lidar, radar, and satellite imagery to assess glacier health, surface velocity, and calving risk.