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Crevasse is also a traditional term for a levee breach.

A crevasse is a deep crack 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. 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 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.

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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51532 news items

Alaska Dispatch News

Alaska Dispatch News
Sun, 29 Mar 2015 12:07:30 -0700

The Alaska Air National Guard and Alaska State Troopers on Saturday came to the aid of a man who fell into a crevasse on Eureka Glacier. Troopers say they took a call just after 5:30 p.m. from 59-year-old Shawn Murphy of North Pole. Murphy reported ...

ABC Online

ABC Online
Sun, 29 Mar 2015 06:03:55 -0700

Melbourne man Jonathan Cawood says he was in the right place at the right time when he rescued a tourist who slipped and fell into a crevasse in New Zealand in January 2014. Mr Cawood, 23, and his friend, Mitchell Stephen, are among those to receive a ...
 
9news.com.au
Thu, 19 Mar 2015 22:26:15 -0700

This is the terrifying moment a Swiss snowboarder fell metres through a crevasse after the snowy ground he was boarding on gave way. Bjorn Hoffman was filming a snowboarding tour along a ridge 4000m above sea level in Valais, Switzerland last March ...

The Inquisitr

The Inquisitr
Thu, 26 Mar 2015 16:02:45 -0700

The images and videos were taken by tourists at the Kjeragbolten boulder, a chunk of rock wedged in the crevasse of the Kjerag Mountain in Rogaland, southern Norway, about 3,500 ft above sea level. The site is a popular tourist destination that can be ...

Telegraph.co.uk

Telegraph.co.uk
Sun, 29 Mar 2015 12:31:37 -0700

In the meantime, though, I want to show you some of the horrors in that crevasse. There is one set of polling data that is now beyond doubt. There is one part of Britain where a seismic change has already taken place, and that is Scotland. In yesterday ...

Al Jazeera America

Al Jazeera America
Sun, 29 Mar 2015 06:52:30 -0700

SWEETWATER, Texas — On the first day of the world's largest rattlesnake roundup in this small West Texas town, Rob McCann hoists a flat, wooden box out of the back of his car. It emits a telltale rattle. “These are my media rattlesnakes,” McCann says.

Yahoo7 News

Yahoo7 News
Sun, 29 Mar 2015 06:30:00 -0700

Victorian Jonathan Cawood has been commended for his brave conduct in assisting with the rescue of a man who slipped and fell into a narrow crevasse in Mariua Falls, New Zealand. Mr Cawood and his friend were preparing to kayak over the falls in ...

Francetv info

Francetv info
Tue, 24 Mar 2015 09:52:30 -0700

FRANCE 3 ALPES. Le glacier de l'aiguille de Péclet, c'est ce secteur situé dans le massif de la Vanoise qui faisait envie à deux skieurs de randonnée de Savoie. Ce mardi 24 mars, peu après 10 heures, l'un d'eux a fait une chute dans une crevasse de 7m.
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