Crevasse is also a traditional term for a levee breach.
A crevasse is a deep crack that forms in a glacier or ice sheet. 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.
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 (150 ft) and as wide as 20 metres (70 ft)[2]
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,[3] where significant summer melting occurs, and the bed of the glacier, where additional water may moisten and lubricate the bed and accelerate ice flow.[4][5] Direct drains of water from the top of a glacier, known as moulins, can also contribute the lubrication and acceleration of ice flow.[5]
Typesedit
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.[6]
Splaying crevasses appear along the edges of a glacier and 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.
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.[6]
Dangersedit
The glacier Taschachferner below the Wildspitze (left, 3.768 m) in Tyrolia in Austria in April 2005. There are some zones with large open crevasses, e.g., the spot-shaped area below the middle of the image and most right. The line marks the ascent track of mountaineers on skis which intentionally avoided these dangerous areas.
Falling into glacial crevasses can be dangerous and life-threatening.[7] Some glacial crevasses (such as on the Khumbu Icefall at Mount Everest) can be 50 metres (160 ft) deep, which can cause fatal injuries upon falling.[8]Hypothermia is often a cause of death when falling into a crevasse.[2]
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.[9]: 343
The danger of falling into a crevasse can be minimized by roping together multiple climbers into a rope team,[9]: 340 and the use of friction knots.[10]
See alsoedit
Bergschrund – Crevasse between moving glacier ice and the stagnant ice or firn above
Bowie Crevasse Field – LandformPages displaying short descriptions with no spaces
Glaciology – Scientific study of ice and natural phenomena involving ice
^van der Veen, C (1990). "Crevasses on Glaciers". Polar Geography. 23 (3): 213–245. doi:10.1080/10889379909377677.
^ ab"Crevasse". National Geographic. Retrieved 2023-06-22.
^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 (18): 1916. Bibcode:2003GeoRL..30.1916B. doi:10.1029/2003gl018034. S2CID 133697259.
^Latimer, Doug (2022-06-20). "MOUNTAIN SAFETY: GLACIER TRAVEL AND CREVASSE RESCUE FOR TWO-PERSON TEAMS". Alpine Club of Canada.
Bibliographyedit
Das SB, Joughin I, Behn MD, Howat IM, King MA, Lizarralde D, Bhatia MP (2008). "Fracture propagation to the base of the Greenland Ice Sheet during supraglacial lake drainage". Science. 320 (5877): 778–781. Bibcode:2008Sci...320..778D. doi:10.1126/science.1153360. hdl:1912/2506. PMID 18420900. S2CID 41582882.
Paterson, W.S.B. (1994). The Physics of Glaciers (3rd ed.). ISBN0-7506-4742-6.
van der Veen CJ (1998). "Fracture mechanics approach to penetration of surface crevasses on glaciers". Cold Regions Science and Technology. 27 (1): 31–47. Bibcode:1998CRST...27...31V. doi:10.1016/s0165-232x(97)00022-0.
External linksedit
Media related to Crevasse (category) at Wikimedia Commons
January 01, 1970
crevasse, confused, with, crevice, also, traditional, term, levee, breach, crevasse, deep, crack, that, forms, glacier, sheet, form, result, movement, resulting, stress, associated, with, shear, stress, generated, when, semi, rigid, pieces, above, plastic, sub. Not to be confused with Crevice Crevasse is also a traditional term for a levee breach A crevasse is a deep crack that forms in a glacier or ice sheet 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 Transverse crevasses Chugach State Park Alaska Contents 1 Description 2 Types 3 Dangers 4 See also 5 References 6 Bibliography 7 External linksDescription edit nbsp A crevasse in Tangra Mountains Antarctica 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 150 ft and as wide as 20 metres 70 ft 2 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 3 where significant summer melting occurs and the bed of the glacier where additional water may moisten and lubricate the bed and accelerate ice flow 4 5 Direct drains of water from the top of a glacier known as moulins can also contribute the lubrication and acceleration of ice flow 5 Types editLongitudinal 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 6 Splaying crevasses appear along the edges of a glacier and 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 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 6 Dangers edit nbsp The glacier Taschachferner below the Wildspitze left 3 768 m in Tyrolia in Austria in April 2005 There are some zones with large open crevasses e g the spot shaped area below the middle of the image and most right The line marks the ascent track of mountaineers on skis which intentionally avoided these dangerous areas Falling into glacial crevasses can be dangerous and life threatening 7 Some glacial crevasses such as on the Khumbu Icefall at Mount Everest can be 50 metres 160 ft deep which can cause fatal injuries upon falling 8 Hypothermia is often a cause of death when falling into a crevasse 2 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 9 343 The danger of falling into a crevasse can be minimized by roping together multiple climbers into a rope team 9 340 and the use of friction knots 10 See also editBergschrund Crevasse between moving glacier ice and the stagnant ice or firn above Bowie Crevasse Field LandformPages displaying short descriptions with no spaces Glaciology Scientific study of ice and natural phenomena involving ice Crevasse rescue Retrieving a climber from a crevasseReferences edit van der Veen C 1990 Crevasses on Glaciers Polar Geography 23 3 213 245 doi 10 1080 10889379909377677 a b Crevasse National Geographic Retrieved 2023 06 22 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 18 1916 Bibcode 2003GeoRL 30 1916B doi 10 1029 2003gl018034 S2CID 133697259 Zwally H J Abdalati W Herring T Larson K Saba J Steffen K 2002 Surface melt induced acceleration of Greenland ice sheet flow Science 297 5579 218 222 Bibcode 2002Sci 297 218Z doi 10 1126 science 1072708 PMID 12052902 S2CID 37381126 a b Colgan W Rajaram H Abdalati W McCutchan C Mottram R Moussavi M S Grigsby S 2016 Glacier crevasses Observations models and mass balance implications Rev Geophys 54 1 119 161 Bibcode 2016RvGeo 54 119C doi 10 1002 2015RG000504 a b Holdsworth G October 1956 Primary Transverse Crevasses Journal of Glaciology 8 52 107 129 doi 10 1017 S0022143000020797 Pasquier M Taffe P Kottmann A Mosimann U Reisten O Hugli O Nov 2014 Epidemiology and mortality of glacier crevasse accidents Injury 45 11 1700 3 doi 10 1016 j injury 2014 07 001 PMID 25082349 Gurubacharya Binaj 2023 04 13 Mount Everest 3 Sherpa climbers missing after falling into deep Khumbu Icefall crevasse Associated Press a b Graydon Don Hanson Kurt eds 1997 Mountaineering The Freedom of the Hills 6th ed The Mountaineers ISBN 0 89886 427 5 Latimer Doug 2022 06 20 MOUNTAIN SAFETY GLACIER TRAVEL AND CREVASSE RESCUE FOR TWO PERSON TEAMS Alpine Club of Canada Bibliography editDas SB Joughin I Behn MD Howat IM King MA Lizarralde D Bhatia MP 2008 Fracture propagation to the base of the Greenland Ice Sheet during supraglacial lake drainage Science 320 5877 778 781 Bibcode 2008Sci 320 778D doi 10 1126 science 1153360 hdl 1912 2506 PMID 18420900 S2CID 41582882 Paterson W S B 1994 The Physics of Glaciers 3rd ed ISBN 0 7506 4742 6 van der Veen CJ 1998 Fracture mechanics approach to penetration of surface crevasses on glaciers Cold Regions Science and Technology 27 1 31 47 Bibcode 1998CRST 27 31V doi 10 1016 s0165 232x 97 00022 0 External links edit nbsp Media related to Crevasse category at Wikimedia Commons Retrieved from https en wikipedia org w index php title Crevasse amp oldid 1210512223, wikipedia, wiki, book, books, library,
