icefall

An icefall is a region of a glacier where moving ice descends over a steep bed, causing the ice to fracture and form a chaotic field of crevasses, seracs, and loose blocks. It typically occurs where a glacier flows from a relatively level area into a steeper section or over a moraine or bedrock obstacle, so the ice is stretched and broken as gravity drives it downward.

In icefalls, the surface may contain crevasses and ice cliffs; below, the fractured ice rearranges into a jumble that can advance or retreat with the seasons. Sun and meltwater can widen crevasses and trigger serac collapse; wind and temperature swings contribute to instability. The overall structure is dynamic, with blocks continually calving and reconfiguring.

Hazards are significant for mountaineers and climbers because blocks can shed without warning, and hidden crevasses can trap individuals. Travel often requires fixed lines, rope teams, and careful route finding to pass around or over the fall. Relative safety improves with early-season clearing, regular monitoring, and experienced judgment about weather and stability.

Icefalls are common on large, active glaciers in high mountains and polar regions. Notable examples include the Khumbu Icefall on Mount Everest in the Himalayas, as well as similar features on glaciers in the Alps, Andes, Alaska, and Greenland. Glaciologists study icefalls to understand glacier dynamics and to improve safety for expeditions; monitoring via field surveys and satellite observations helps anticipate changes in activity.