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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. 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.

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.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
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685 news items

20minutes.fr

7sur7
Fri, 22 Aug 2014 03:53:02 -0700

Selon la protection civile locale, cette fissure a été causée par un tremblement de terre qui a frappé la région dimanche passé. Un avis qui ne partagent pas les géologues de l'Université du Sonora. Pour eux, une digue construite en amont de la ...

Dual Pixels

Dual Pixels
Sun, 21 Sep 2014 12:41:15 -0700

The one control crevasse that Anomaly 2 doesn't fall into is that because your vehicles, besides plotting out their routes are out of your control you don't have to worry about slowly scrolling around with a analog stick to replicate a mouse's much ...
 
New York Times
Fri, 19 Sep 2014 13:14:28 -0700

Along the way she learned that Mr. Koubek was a graduate of Reed College with a degree in literature and a Fulbright scholar who scales icefalls for fun and once survived a 60-foot fall into a glacier crevasse. By New Year's Day, she had run the ...

Le Dauphiné Libéré

Le Dauphiné Libéré
Sun, 31 Aug 2014 10:03:45 -0700

Quatre alpinistes sont morts dimanche 31 août après avoir chuté dans une crevasse du massif de Valtellina, dans les Alpes italiennes, au nord-est de Milan, relaie RTL. Il s'agirait d'une cordée de six personnes qui avaient décidé de partir à l ...
 
Fresno Bee
Mon, 08 Sep 2014 22:03:45 -0700

At the bottom of the ravine is the Dudan Crevasse, a vertigo-inducing gash that plummets at least another 350 feet. I have visited the area twice in the past two years. In May 2013, the first time I went, the school did not exist. By August, it had ...

WalesOnline

WalesOnline
Sat, 20 Sep 2014 22:34:05 -0700

When his professional career was cut short by injury, he sunk to an all time low but turned his life around to scale the world's highest mountains and cross its polar opposites. And now the former Newport Gwent Dragon, and Pontypridd RFC player's ...
 
Le Dauphiné Libéré
Tue, 02 Sep 2014 21:03:48 -0700

Suivez toute l'actualité de votre région en continu sur le support de votre choix. Rester connecté avec les infos, images et vidéos à Grenoble, Annecy, Chambéry, Avignon, Valence, Gap et plus généralement en Isère, Savoie, Haute-Savoie, Ain, Drôme, ...

Geek

Geek
Sat, 23 Aug 2014 06:41:15 -0700

You can only imagine how much more troubling it would be if this crevasse has opened up a few miles to the east in Hermosillo. As it is, farm workers have been diverting around Highway 26, but many of the smaller side roads in the area are in poor shape.
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