Crevasse

A crevasse is a deep crack in an ice sheet or glacier (as opposed to a crevice, which forms in rock). Crevasses form as a result of the movement and resulting stress associated with the shear stress generated when two semi-rigid pieces above a plastic substrate have different rates of movement. The resulting intensity of the shear stress causes a breakage along the faces.

Crevasses often have vertical or near-vertical walls, which can then melt and create seracs, arches, and other ice formations. These walls sometimes expose layers that represent the glacier's stratigraphy.

Crevasses are more narrow at depth as it is here that pieces of the glacier may rub and break against each other. Crevasse size often depends upon the amount of liquid water present in the glacier. A crevasse may be as deep as 45 meters, as wide as 20 meters, and can be up to several hundred meters long.

The presence of water in a crevasse can significantly increase its penetration. Water-filled crevasses may reach the bottom of glaciers or ice sheets and provide a direct hydrologic connection between the surface, where significant summer melting occurs, and the bed of the glacier, where additional water may lubricate the bed and accelerate ice flow.