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Glacial ripping: ge...
Glacial ripping: geomorphological evidence from Sweden for a new process of glacial erosion
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- Hall, Adrian M. (författare)
- Stockholms universitet,Institutionen för naturgeografi
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Krabbendam, M. (författare)
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- van Boeckel, Mikis (författare)
- Stockholms universitet,Institutionen för naturgeografi
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Goodfellow, B. W. (författare)
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- Hättestrand, Clas (författare)
- Stockholms universitet,Institutionen för naturgeografi
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- Heyman, Jakob (författare)
- Gothenburg University,Göteborgs universitet,Institutionen för geovetenskaper,Department of Earth Sciences
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Palamakumbura, R. N. (författare)
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- Stroeven, Arjen P. (författare)
- Stockholms universitet,Institutionen för naturgeografi
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Naslund, J. O. (författare)
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(creator_code:org_t)
- 2020-06-05
- 2020
- Engelska.
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Ingår i: Geografiska Annaler Series a-Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 2:4, s. 333-53
- Relaterad länk:
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https://doi.org/10.1...
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https://su.diva-port... (primary) (Raw object)
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https://gup.ub.gu.se...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- In low relief Precambrian gneiss terrain in eastern Sweden, abraded bedrock surfaces were ripped apart by the Fennoscandian Ice Sheet. The resultantboulder spreadsare covers of large, angular boulders, many with glacial transport distances of 1-100 m. Boulder spreads occur alongside partly disintegrated roches moutonnees and associated fracture caves, and are associated withdisrupted bedrock, which shows extensive fracture dilation in the near surface. These features are distributed in ice-flow parallel belts up to 10 km wide and extend over distances of >500 km. Our hypothesis is that the assemblage results from (1) hydraulic jacking and bedrock disruption, (2) subglacial ripping and (3) displacement, transport and final deposition of boulders. Soft sediment fills indicate jacking and dilation of pre-existing bedrock fractures by groundwater overpressure below the ice sheet. Overpressure reduces frictional resistance along fractures. Where ice traction overcomes this resistance, the rock mass strength is exceeded, resulting in disintegration of rock surfaces and ripping apart into separate blocks. Further movement and deposition create boulder spreads and moraines. Short boulder transport distances and high angularity indicate that glacial ripping operated late in the last deglaciation. The depths of rock mobilized in boulder spreads are estimated as 1-4 m. This compares with 0.6-1.6 m depths of erosion during the last glaciation derived from cosmogenic nuclide inventories of samples from bedrock surfaces without evidence of disruption. Glacially disrupted and ripped bedrock is also made ready for removal by future ice sheets. Henceglacial rippingis a highly effective process of glacial erosion.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences (hsv//eng)
Nyckelord
- Glacial ripping
- groundwater overpressure
- Fennoscandian ice sheet
- ice-sheet
- ribbed moraine
- deglaciation
- greenland
- drainage
- scale
- paleoseismicity
- stream
- fennoscandia
- deformation
- Physical Geography
- Geology
- Glacial ripping
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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