| Term: | Crevasse |
| Definition: |
Open fissure in the glacier surface. NSIDCCryosphere
A crack or series of cracks that open in the surface of a moving glacier in response to differential stresses caused by glacier flow. They range in shape from linear to arcuate, in length from feet to miles. Their orientation may be in any direction with respect to the glacier flow. The deepest crevasses may exceed 100 feet. A crack formed in glacier ice when tensile stresses exceed the tensile strength of the ice. The tensile stresses, and the tensile strength of the ice, are variable, and compressive stress at depth is believed to play a role in limiting the depth to which surface crevasses propagate. This depth can be up to a few tens of metres, or more if the crevasse is filled with water. Crevasses are conduits for the transfer of water, including surface meltwater, to the glacier interior and sometimes the glacier bed; see moulin. When crevasses in floating ice fill with surface meltwater, they may propagate to the base, causing the ice shelf or floating tongue to disintegrate. The fragments may contribute to an ice m IHPGlacierMassBalance Fissure formed in a glacier but not applied in place-names, cf. chasm. UKAntarcticTerms Fissure in a glacier. WMOHydrology A deep V-shaped cleft formed in the upper brittle part of a glacier as a result of the fracture of ice undergoing extension. For various types of crevasses refer to longitudinal crevasse, transverse crevasse, en-echelon crevasse and bergschrund. Swisseduc A deep rift in a glacier, or in any other form of land ice, caused by its motion. AMSglossary (1) Opening on a levee that allows for the drainage of water from the floodplain to the stream channel. (2) Fracture on the brittle surface of a glacier. PhysicalGeography A fissure formed in a glacier. Crevasses are often hidden by snow bridges. SPRI Crevasses are open fissures in glacier ice. Crevasses form where the speed of the ice is variable, such as in icefalls and at valley bends. The surface may appear blistered with crevasses where the ice flows over bedrock knobs and ridges. Crevasses are a glacier's most awesome features and are a constant hazard for climbers. They form where adjacent parts of a glacier are moving at different speeds. This unequal rate of flow produces stresses in the ice that cause it to break. Groups of crevasses often form where the glacier flows over a steep place in its bed. The ice moves faster here, and pulls apart, and a crevasse is formed. Although a large crevasse may seem to be bottomless to the observer, most crevasses are less than 100 feet deep because ice pressure tends to close the open spaces in the ice below that depth. GCW |