Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping
Glacial ripping involves glaciotectonic disintegration of rock hills and extensive removal of rock at the ice-sheet bed, triggered by hydraulic jacking caused by fluctuating water pressures. Evidence from eastern Sweden shows that glacial ripping caused significant subglacial erosion during the fina...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2023-02-01
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| Series: | Journal of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S0022143022000491/type/journal_article |
| _version_ | 1811155727092285440 |
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| author | Maarten Krabbendam Fabio Dioguardi Christian Arnhardt Sam Roberson Adrian M. Hall |
| author_facet | Maarten Krabbendam Fabio Dioguardi Christian Arnhardt Sam Roberson Adrian M. Hall |
| author_sort | Maarten Krabbendam |
| collection | DOAJ |
| description | Glacial ripping involves glaciotectonic disintegration of rock hills and extensive removal of rock at the ice-sheet bed, triggered by hydraulic jacking caused by fluctuating water pressures. Evidence from eastern Sweden shows that glacial ripping caused significant subglacial erosion during the final deglaciation of the Fennoscandian ice sheet, distinct from abrasion and plucking (quarrying). Here we analyse the ice drag forces exerted onto rock obstacles at the base of an ice sheet, and the resisting forces of such rock obstacles: glaciotectonic disintegration requires that ice drag forces exceed the resisting forces of the rock obstacle. We consider rock obstacles of different sizes, shapes and fracture patterns, informed by natural examples from eastern Sweden. Our analysis shows that limited overpressure events, unfavourable fracture patterns, low-transmissivity fractures, slow ice and streamlined rock hamper rock hill disintegration. Conversely, under fast ice flow and fluctuating water pressures, disintegration is possible if the rock hill contains subhorizontal, transmissive fractures. Rock steps on previously smooth, abraded surfaces, caused by hydraulic jacking, also enhance drag forces and can cause disintegration of a rock hill. Glacial ripping is a physically plausible erosion mechanism, under realistic glaciological conditions prevalent near ice margins. |
| first_indexed | 2024-04-10T04:39:25Z |
| format | Article |
| id | doaj.art-3c817f51da64492bba4fe6abb0f1b5ba |
| institution | Directory Open Access Journal |
| issn | 0022-1430 1727-5652 |
| language | English |
| last_indexed | 2024-04-10T04:39:25Z |
| publishDate | 2023-02-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Journal of Glaciology |
| spelling | doaj.art-3c817f51da64492bba4fe6abb0f1b5ba2023-03-09T12:41:21ZengCambridge University PressJournal of Glaciology0022-14301727-56522023-02-016910311910.1017/jog.2022.49Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial rippingMaarten Krabbendam0Fabio Dioguardi1Christian Arnhardt2Sam Roberson3Adrian M. Hall4British Geological Survey, Lyell Centre, Edinburgh, UKBritish Geological Survey, Lyell Centre, Edinburgh, UKBritish Geological Survey, Keyworth, Nottingham, UKGeological Survey of Northern Ireland, Belfast, Northern Ireland, UKDepartment of Physical Geography, University of Stockholm, Stockholm, Sweden Institute of Geography, University of Edinburgh, Edinburgh, UKGlacial ripping involves glaciotectonic disintegration of rock hills and extensive removal of rock at the ice-sheet bed, triggered by hydraulic jacking caused by fluctuating water pressures. Evidence from eastern Sweden shows that glacial ripping caused significant subglacial erosion during the final deglaciation of the Fennoscandian ice sheet, distinct from abrasion and plucking (quarrying). Here we analyse the ice drag forces exerted onto rock obstacles at the base of an ice sheet, and the resisting forces of such rock obstacles: glaciotectonic disintegration requires that ice drag forces exceed the resisting forces of the rock obstacle. We consider rock obstacles of different sizes, shapes and fracture patterns, informed by natural examples from eastern Sweden. Our analysis shows that limited overpressure events, unfavourable fracture patterns, low-transmissivity fractures, slow ice and streamlined rock hamper rock hill disintegration. Conversely, under fast ice flow and fluctuating water pressures, disintegration is possible if the rock hill contains subhorizontal, transmissive fractures. Rock steps on previously smooth, abraded surfaces, caused by hydraulic jacking, also enhance drag forces and can cause disintegration of a rock hill. Glacial ripping is a physically plausible erosion mechanism, under realistic glaciological conditions prevalent near ice margins.https://www.cambridge.org/core/product/identifier/S0022143022000491/type/journal_articleGlacier hydrologyprocesses and landforms of glacial erosionsubglacial processessubglacial sediments |
| spellingShingle | Maarten Krabbendam Fabio Dioguardi Christian Arnhardt Sam Roberson Adrian M. Hall Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping Journal of Glaciology Glacier hydrology processes and landforms of glacial erosion subglacial processes subglacial sediments |
| title | Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping |
| title_full | Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping |
| title_fullStr | Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping |
| title_full_unstemmed | Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping |
| title_short | Drag forces at the ice-sheet bed and resistance of hard-rock obstacles: the physics of glacial ripping |
| title_sort | drag forces at the ice sheet bed and resistance of hard rock obstacles the physics of glacial ripping |
| topic | Glacier hydrology processes and landforms of glacial erosion subglacial processes subglacial sediments |
| url | https://www.cambridge.org/core/product/identifier/S0022143022000491/type/journal_article |
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