What is a Crevasse?

A crevasse is a crack, crevice, or fracture in a glacier or moving mass of ice that forms from the movement and stress of the glacier, especially as it moves downhill. Stress in the ice caused by the glacier’s movement causes crevasses to open and close. Crevasses usually form in the upper 150 feet of a glacier where the ice is more brittle than deeper ice, which tends not to break and fracture as the glacier moves.

Crevasses also form from the speed of a glacier as it creeps downhill. Ice in the middle of a glacier tends to move more quickly than along the edges where it catches and grabs the underlying rock surface and cause crevasses to gape open. Crevasses usually have vertical walls and are up to 150 feet deep and as wide as 70 feet. Crevasses, however, are usually narrow and thin, forming extreme hazards for mountaineers crossing a glacier.

Crevasses have three distinct forms.

• Transverse Crevasses The most common type of crevasses are transverse crevasses, which stretch parallel to the flow of the glacier and form fractures that may completely cross the glacier. Transverse crevasses occur on steeper glacial terrain rather than flatter areas.
• Spashing Crevasses Splashing crevasses form along the edges of a glacier, extending from the edge uphill and bending with the flow of the glacier.
• Longitudinal Crevasses Longitudinal crevasses, the third type, form parallel to the flow of the glacier.

Crevasses pose a huge danger to climbers in the mountains since a climber who falls into a crevasse usually dies. Narrow crevasses are additionally dangerous because the top can be filled in with drifted snow forming a snow bridge, which may or may not be stable. Snow bridges can break under the weight of a passing climber. The snow makes the crevasses invisible to the inexperienced eye. Mountaineeers who climb and cross glaciers and icecaps learn essential glacier travel skills, such as how to cross a glacier with a partner and a climbing rope, and how to do crevasse rescue for yourself or your partner. These are essential climbing skills that must be regularly practiced for safe glacial travel.