Crevasse

Crevasses often have vertical or near-vertical walls, which can then melt and create seracs, arches, and other ice formations.

Water-filled crevasses may reach the bottom of glaciers or ice sheets and provide a direct hydrologic connection between the surface,[3] where significant summer melting occurs, and the bed of the glacier, where additional water may moisten and lubricate the bed and accelerate ice flow.

[4][5] Direct drains of water from the top of a glacier, known as moulins, can also contribute the lubrication and acceleration of ice flow.

[7] Some glacial crevasses (such as on the Khumbu Icefall at Mount Everest) can be 50 metres (160 ft) deep, which can cause fatal injuries upon falling.

Occasionally a snow bridge over an old crevasse may begin to sag, providing some landscape relief, but this cannot be relied upon.

Transverse crevasses, Chugach State Park , Alaska
A crevasse in Tangra Mountains , Antarctica
A man crosses a crevasse in Easton Glacier , Mount Baker , in the North Cascades , Washington
The glacier Taschachferner below the Wildspitze (left, 3.768 m) in Tyrolia in Austria in April 2005. There are some zones with large open crevasses, e.g., the spot-shaped area below the middle of the image and most right. The line marks the ascent track of mountaineers on skis which intentionally avoided these dangerous areas.