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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.
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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1247 news items

Sky News Australia

Times Colonist
Wed, 13 Aug 2014 02:59:48 -0700

A sixth climber was spotted at the bottom of a crevasse. August is the height of the climbing season on Mont Blanc, where even in the warmest months storms can strike quickly. High winds buffeted the area where the group fell, said Jean-Baptiste ...
 
New Tang Dynasty Television
Sun, 03 Aug 2014 22:03:45 -0700

What's 'exploratory alpinism'? It's setting off into remote areas in search of big, unclimbed walls, a la Graham Zimmerman, one of Alaska's current pioneering mountaineers. Check out his thoughts on the topic then follow him into the Revelations Range ...

Indian Express

Indian Express
Tue, 19 Aug 2014 15:41:15 -0700

It was afternoon when Prasad suddenly fell into a crevasse. A search operation was conducted and even officials from other states were engaged in it. But Prasad could not be traced. The officials then declared him dead and simultaneously his family was ...

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 ...

Europe1

Europe1
Tue, 19 Aug 2014 19:48:45 -0700

INFO. Six alpinistes portés disparus depuis mardi soir dans le Mont-Blanc ont été retrouvés morts mercredi. Cinq corps avaient été retrouvés inertes dès mercredi matin tandis qu'une sixième dépouille a été retrouvée dans une crevasse mercredi après ...

Fox News

Farmington Daily Times
Wed, 20 Aug 2014 17:00:00 -0700

If one climber falls into a crevasse, the other climbers in the rope team fall to the snow and dig in with their axes and crampons to hold the fall. The fallen climber then ascends his or her rope or is pulled out. For more information about Mount ...
 
Valley News
Wed, 20 Aug 2014 20:41:18 -0700

Having summitted France's 15,781-foot Mont Blanc, the highest peak in the Alps, Steinberg was skiing down a glacier during the descent when he swerved to avoid a crevasse and crashed, fracturing his tibia and tearing his ACL. Bedridden following ...

World Policy Institute (blog)

World Policy Institute (blog)
Thu, 21 Aug 2014 07:15:00 -0700

In an age of GPS-reliance, facing the North Pole's “drifting trees,” and remembering their relevance to early polar exploration is like peering into a crevasse in time—the artist finds the ignition of, not just one, but timelines of ideas and theories ...
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