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Crevasse is also a traditional term for a levee breach.
Crossing a crevasse on the Easton Glacier, Mount Baker, in the North Cascades, Washington

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.

Description[edit]

Crevasses often have vertical or near-vertical walls, which can then melt and create seracs, arches, and other ice formations.[1] These walls sometimes expose layers that represent the glacier's stratigraphy. They are widely distributed across Antarctica and 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 metres, as wide as 20 metres, and can be up to several hundred metres long.

A crevasse may be covered, but not necessarily filled, by a snow bridge made of the previous years' accumulation and snow drifts. The result is that crevasses are rendered invisible, and thus potentially lethal to anyone attempting to navigate their way across a glacier. Occasionally a snow bridge over an old crevasse may begin to sag providing some landscape relief, but this cannot be relied upon. Anyone planning to travel on a glacier should be trained in crevasse rescue.

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.

Types of crevasses[edit]

  • Transverse crevasses are the most common crevasse type and they form in a zone of longitudinal extension where the principal stresses are normal to the direction of glacier flow, creating extensional tensile stress. These crevasses stretch across the glacier transverse to the flow direction, or cross-glacier. They generally form where a valley becomes steeper.[2]
  • Splashing crevasses form as a result of shear stress from the margin of the glacier, and longitudinal compressing stress from lateral extension. They extend from the margin of the glacier and are concave up with respect to glacier flow, making an angle less than 45° with the margin. At the centre line of the glacier, there is zero pure shear from the margins, so this area is typically crevasse-free.
  • Longitudinal crevasses form parallel to flow where the glacier width is expanding. They develop in areas of compressing stress, such as where a valley widens or bends. They are typically concave down-glacier, and form an angle greater than 45° with the margin.[2]

Gallery[edit]

Crevasses around the world
Crevasse on the Gorner Glacier, Zermatt, Switzerland 
Measuring snowpack in a crevasse on the Easton Glacier, Mount Baker, North Cascades, United States 
Exploring the bottom of a crevasse in Antarctica 
Crevasse on the Ross Ice Shelf, January 2001 
Crevasses on the Upper Price Glacier of Mt. Shuksan, North Cascades, WA. Photo taken August 2011 
Split-boarder skinning up past open crevasses on the Coleman Glacier of Mt. Baker. Photo taken October 2009 
Looking down into a crevasse on Mt. Rainier, Cascade range, WA. Photo taken Mid August 2009 
Crevasses on Mt. Rainier. Photo taken from the Disappointment Cleaver Route on Mt. Rainier. Photo taken August 2009 
Mountaineers crossing a crevasse on Mt. Rainier. Photo taken August 2009 
Ladder bridging a crevasse on Mt. Rainier. Photo taken Aug. 2009 

See also[edit]

References[edit]

  1. ^ van der Veen, C (1990). "Crevasses on Glaciers". Polar Geography 23 (3): 213–245. 
  2. ^ a b Holdsworth, G (October 1956). "Primary Transverse Crevasses". Journal of Glaciology 8 (52): 107–129. 

Bibliography[edit]

  • Paterson, W.S.B., 1994, The Physics of Glaciers, 3rd edition, ISBN 0-7506-4742-6.
  • Boon, S., M.J. Sharp, 2003, The role of hydrologically-driven ice fracture in drainage system evolution on an Arctic glacier, Geophysical Research Letters, 30, pp. 1916.
  • 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. 218–222.
  • Mountaineering: The Freedom of the Hills, 5th edition. ISBN 0-89886-309-0.
  • "Crevasse." Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 17 Oct. 2010.
  • Das, S. B., I. Joughin, M.D. Behn, I.M. Howat, M.A. King, D. Lizarralde, M.P. Bhatia, 2008, Fracture propagation to the base of the Greenland Ice Sheet during supraglacial lake drainage, Science, 320, pp. 778.

External links[edit]

  • Media related to Crevasse at Wikimedia Commons

Templates[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Crevasse — Please support Wikipedia.
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556 news items

The Guardian

The Guardian
Tue, 15 Jul 2014 21:59:57 -0700

Australian soldier killed in crevasse fall on New Zealand's Mount Cook. 44-year-old man fell 30m to 40m on a training exercise in the Grand Plateau area and was one of a party of 10, police say. Share ...

Wawa-news.com

Wawa-news.com
Sat, 26 Jul 2014 06:52:30 -0700

The crews of an RCAF Griffon helicopter and Hercules aircraft assisted the Ontario Provincial Police (OPP) with an early morning evacuation of an injured hiker from a deep crevasse 90 kilometers north of Sault Ste. Marie, on Friday, July 25th. At 6:30 ...

The Age

The Age
Wed, 16 Jul 2014 21:07:30 -0700

Rescue vision from Mt Cook (00:41). RAW VISION: An onboard camera captures the dramatic landscape where an Australian soldier fell into a crevasse on Mount Cook in New Zealand. 17/07/14. Australian soldier killed in Mount Cook NZ fall was instructor, ...

The Age

The Age
Tue, 15 Jul 2014 22:35:15 -0700

Unseasonably warm weather a factor in Australian Soldier falling down a crevasse, says NZ conservation minster Nick Smith, who had just flown over the area in a helicopter. Credits Video Journalist: Colin Cosier Close 16/07/14. Australian soldier dies ...

WA today

WA today
Wed, 16 Jul 2014 21:10:40 -0700

Rescue vision from Mt Cook (00:41). RAW VISION: An onboard camera captures the dramatic landscape where an Australian soldier fell into a crevasse on Mount Cook in New Zealand. 17/07/14. Australian soldier killed in Mount Cook NZ fall was instructor, ...

Yahoo!7 News

Yahoo!7 News
Tue, 15 Jul 2014 21:12:54 -0700

An Australian soldier has died after falling down a 40-metre crevasse at New Zealand's highest mountain, it has been confirmed. The 44-year-old soldier fell down a crevasse at Aoraki/Mt Cook, around 12.30pm local time. He died during a survival ...

Irish Independent

Irish Independent
Mon, 28 Jul 2014 18:30:00 -0700

Last week, two Finnish climbers aged 25 and 40 were also killed on Mont Blanc, after slipping into a crevasse. A spokesman from the Department of Foreign Affairs confirmed last night that it was providing consular assistance to both of the Irishmen's ...
 
The Courier
Mon, 28 Jul 2014 06:30:00 -0700

Gary Francis, 44, who served with 45 Commando in Arbroath and has family in the town, fell 40 metres down a crevasse to his death during a training exercise on Mount Cook. Sergeant Francis, of the Australian Army's 2nd Commando Regiment, was leading ...
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