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Crevasse is also a traditional term for a levee breach.

A crevasse is a deep crack, or fracture, found in an ice sheet or glacier, as opposed to a crevice that 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. 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 up to several hundred metres long.[citation needed]

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.[citation needed]

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 moisten and lubricate the bed and accelerate ice flow.[citation needed]

Types of crevasses[edit]

  • Longitudinal crevasses form parallel to flow where the glacier width is expanding. They develop in areas of tensile stress, such as where a valley widens or bends. They are typically concave down and form an angle greater than 45° with the margin.[2]
  • Splashing crevasses result from shear stress from the margin of the glacier and longitudinal compressing stress from lateral extension. They extend from the glacier's margin 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.[citation needed]
  • Transverse crevasses are the most common crevasse type. They form in a zone of longitudinal extension where the principal stresses are parallel 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]

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 skiing 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. doi:10.1080/10889379909377677. 
  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.
  • Colgan, W., H. Rajaram, W. Abdalati, C. McCutchan, R. Mottram, M. S. Moussavi, and S. Grigsby (2016), Glacier crevasses: Observations, models, and mass balance implications, Rev. Geophys., 54, doi: 10.1002/2015RG000504

External links[edit]

  • Media related to Crevasses at Wikimedia Commons

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Crevasse — Please support Wikipedia.
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50 feet down in a crevasse after fall, Chamonix

On February 17, 2015 I was snowboarding off-piste on Glacier des Rognons in the Grands Montets resort in Chamonix and I fell into a deep crevasse.

24-05-2015 Chute en crevasse a ski et secours sur le glacier du Strahlhorn.

Chute et secours en crevasse le 24/05/2015 en descendant du Strahlhorn. Merci au guide suisse Yvan Duc et deux de ses stagiaires Armand et Oriel pour leur ...

Climber films 20m crevasse fall in Himalayas - BBC News

Subscribe to BBC News www.youtube.com/bbcnews Watch this dramatic video as seriously injured US climber John All struggles to survive after falling 70 feet ...

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Helmet Cam Captures Skier Falling Into Glacial Crevasse

Helmet camera captures footage of Benjamin Spilthooren as he skied down the Strah Strahlhorn mountain in the Pennine Alps and fell into a glacial crevasse.

Drone flies in crevasse

Flyability partnered with the team from Zermatt Mountain Rescue of the Zermatt Glacier in the Swiss Alps to explore crevasses situated at an altitude of 3'500 ...

Inside a crevasse on Mt. Rainier's Nisqually Glacier

My BCC (Basic Climbing Class) team lowers me into a small crevasse on the Nisqually Glacier on Mt. Rainier to practice the "z-pully", a method of crevasse ...

2 Person Rope Team Crevasse Rescue

This video shows my variation for 1 on 1 Crevasse Rescue. Presenter - Darrell Weston Fallen Climber - Dana Tofell Videographer - Matt Blecharz.

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Everest Million - Crossing an Everest crevasse - heart in mouth!

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