Crossing a crevasse on the Easton Glacier, Mount Baker, in the North Cascades, Washington

A crevasse is a fracture in a glacier caused by a large tensile stress at or near the glacier's surface. Mount Baker (elevation) is an active glaciated andesitic Stratovolcano in the Cascade Volcanic Arc and the Cascades of The North Cascades are a section of the Cascade Range of western North America. Washington ( is a state in the Pacific Northwest region of the United States. A fracture is the (local separation of an object or material into two or more pieces under the action of stress. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Stress is a measure of the average amount of Force exerted per unit Area. Accelerations in glacier speed cause extension and can initiate a crevasse. Crevasses often have vertical or near-vertical walls, which can then melt and create seracs, arches, etc. A serac (originally from Swiss French sérac, a type of crumbly white Cheese) is a block or column of Ice formed by intersecting Crevasses ; these walls sometimes expose layers that represent the glacier's stratigraphy. Stratigraphy, a branch of Geology, studies rock layers and layering ( stratification)

• Transverse crevasses are the most common type crevasse type and they form in a zone of extension where the glacier is accelerating as it moves downslope. These crevasses stretch across the glacier transverse to the flow direction.

• Marginal crevasses extend diagonally from the edge of the glacier pointing upglacier. These crevasses form because of the higher speeds of the glacier near its centerline relative to its margin.

• Longitudinal crevasses form parallel to flow where the glacier width is expanding.

• A bergschrund is a crevasse that divides moving glacier ice below the bergschrund from the stagnant ice above it and may extend to bedrock below. A bergschrund is a Crevasse that forms where the moving glacier ice separates from the stagnant ice above Bedrock is the native consolidated rock underlying the surface of a terrestrial planet usually the Earth.

A crevasse may be covered, but not necessarily filled, by a snow bridge made of the previous year's snow. Falling into a hidden crevasse that is covered by a weak snow bridge is thus a danger for mountaineers. “Alpinist” redirects here See also Alpinist (magazine Mountaineering is the Sport, Hobby or Profession of Anyone planning to travel on a glacier should be trained in crevasse rescue. Crevasse rescue is the process of retrieving a climber from a Crevasse in a Glacier.

Fracture mechanics has been used to study the growth of crevasses on glaciers. Fracture mechanics is the field of Mechanics concerned with the study of the formation of cracks in materials The maximum depth of a dry crevasse, predicted using an estimate of the fracture toughness of ice, is about 30 m. In Materials science, fracture toughness is a property which describes the ability of a material containing a crack to resist Fracture, and is one of the most important Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia However, crevasses deeper than 30 m have been observed. The presence of water in a crevasse can significantly increase its penetration. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 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. An ice sheet is a mass of Glacier Ice that covers surrounding terrain and is greater than 50000 km² (20000 mile²) Hydrology (from Greek Yδωρ hudōr, "water" and λόγος logos, "study" is the study of the movement distribution and quality of Melting is a process that results in the phase change of a substance from a Solid to a Liquid. Lubrication is the process or technique employed to reduce wear of one or both surfaces in close proximity and moving relative to each another by interposing a substance called

"Crevasse" is also a traditional term for a levee failure, such as those along the Mississippi River. Dike (constructionEmbankmentA levee, levée, dike (or dyke) embankment, floodbank or stopbank is a natural or artificial The Mississippi River is the second longest River in the United States, with a length of from its source in Lake Itasca in Minnesota to

See also

• Snow bridge

Gallery

Crevasse on the Gorner Glacier, Zermatt, Switzerland

Measuring snowpack in a crevasse on the Easton Glacier, Mount Baker, North Cascades, U.S.

Exploring the bottom of a crevasse in Antarctica

Crevasse on the Ross Ice Shelf, January 2001. For another meaning see Avalanche snow bridge Snow bridge is an arc across a Crevasse, a crack in rock a Creek, or some other The Gorner Glacier (Gornergletscher is a valley Glacier found on the Monte Rosa massif close to Zermatt in the canton of Valais, Zermatt (Praborgne is a municipality in the district of Visp in the canton of Valais in Switzerland. Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation Mount Baker (elevation) is an active glaciated andesitic Stratovolcano in the Cascade Volcanic Arc and the Cascades of The North Cascades are a section of the Cascade Range of western North America. The United States of America —commonly referred to as the The Ross Ice Shelf ( is the largest Ice shelf of Antarctica (an area of roughly 487 000 km² and about 800 km across about the size of France)

References

Paterson, W. S. B. , 1994, The Physics of Glaciers, 3rd edition, ISBN 0750647426.

van der Veen, C. J. , 1998, Fracture mechanics approach to penetration of surface crevasses on glaciers, Cold Regions Science and Technology, 27, pp. 31-47.

Zwally, H. J. , W. Abdalati, T. Herring, K. Larson, J. Saba, K. Steffen, 2002, Surface melt-induced acceleration of Greenland ice-sheet flow, Science, 297, pp. The Greenland Ice Sheet is a vast body of ice covering 171 million km² roughly 80% of the surface of Greenland. Science is the Academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious Scientific 218-222.

Mountaineering: The Freedom of the Hills, 5th edition. Mountaineering The Freedom of the Hills is often considered the standard Textbook for Mountaineering and Climbing. ISBN 0-89886-309-0.