Drumlinization and drumlin-forming instabilities: viscous till mechanisms
Abstract Glacially induced flow naturally tends to thin and extended till cover through shock formation, even in the absence of longitudinal gradients in the applied stress. Thicker till cover has an increased effective pressure at its surface and base, a lower sliding velocity or deformation rate a...
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Cambridge University Press (CUP)
1998
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Online Access: | http://dx.doi.org/10.1017/s002214300000263x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300000263X |
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crcambridgeupr:10.1017/s002214300000263x 2024-09-15T18:12:27+00:00 Drumlinization and drumlin-forming instabilities: viscous till mechanisms Hindmarsh, Richard C. A. 1998 http://dx.doi.org/10.1017/s002214300000263x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300000263X en eng Cambridge University Press (CUP) Journal of Glaciology volume 44, issue 147, page 293-314 ISSN 0022-1430 1727-5652 journal-article 1998 crcambridgeupr https://doi.org/10.1017/s002214300000263x 2024-07-31T04:04:20Z Abstract Glacially induced flow naturally tends to thin and extended till cover through shock formation, even in the absence of longitudinal gradients in the applied stress. Thicker till cover has an increased effective pressure at its surface and base, a lower sliding velocity or deformation rate and above a critical thickness, a decrease in wave velocity with thickness, leading to reverse-facing shocks moving downstream. For sliding and for some theologies of internal deformation, a decrease in sediment flux with thickness occurs, implying backward-moving kinematic waves and reverse-facing, reverse-moving shock. Downstream-facing shocks are also formed which move upstream if the till is sliding and downstream if the till is deforming internally. Eventually, shocks coalesce, leaving an upstream-lacing shock for sliding and a downstream-facing shock for internal deformation. It is observed that some drumlins have downstream blunt ends only. Fairly realistic three-dimensional drumlin shapes can be produced from symmetric sediment bodies and barchan shapes can be produced from linear forms perpendicular to the ice-sheet flow. The fact that viscous theories produce drumlinoid forms suggests that on this scale till behaves viscously and the the lower length scale for drumlins represents the plastic/viscous transition scale. Article in Journal/Newspaper Ice Sheet Journal of Glaciology Cambridge University Press Journal of Glaciology 44 147 293 314 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
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English |
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Abstract Glacially induced flow naturally tends to thin and extended till cover through shock formation, even in the absence of longitudinal gradients in the applied stress. Thicker till cover has an increased effective pressure at its surface and base, a lower sliding velocity or deformation rate and above a critical thickness, a decrease in wave velocity with thickness, leading to reverse-facing shocks moving downstream. For sliding and for some theologies of internal deformation, a decrease in sediment flux with thickness occurs, implying backward-moving kinematic waves and reverse-facing, reverse-moving shock. Downstream-facing shocks are also formed which move upstream if the till is sliding and downstream if the till is deforming internally. Eventually, shocks coalesce, leaving an upstream-lacing shock for sliding and a downstream-facing shock for internal deformation. It is observed that some drumlins have downstream blunt ends only. Fairly realistic three-dimensional drumlin shapes can be produced from symmetric sediment bodies and barchan shapes can be produced from linear forms perpendicular to the ice-sheet flow. The fact that viscous theories produce drumlinoid forms suggests that on this scale till behaves viscously and the the lower length scale for drumlins represents the plastic/viscous transition scale. |
format |
Article in Journal/Newspaper |
author |
Hindmarsh, Richard C. A. |
spellingShingle |
Hindmarsh, Richard C. A. Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
author_facet |
Hindmarsh, Richard C. A. |
author_sort |
Hindmarsh, Richard C. A. |
title |
Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
title_short |
Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
title_full |
Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
title_fullStr |
Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
title_full_unstemmed |
Drumlinization and drumlin-forming instabilities: viscous till mechanisms |
title_sort |
drumlinization and drumlin-forming instabilities: viscous till mechanisms |
publisher |
Cambridge University Press (CUP) |
publishDate |
1998 |
url |
http://dx.doi.org/10.1017/s002214300000263x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300000263X |
genre |
Ice Sheet Journal of Glaciology |
genre_facet |
Ice Sheet Journal of Glaciology |
op_source |
Journal of Glaciology volume 44, issue 147, page 293-314 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s002214300000263x |
container_title |
Journal of Glaciology |
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44 |
container_issue |
147 |
container_start_page |
293 |
op_container_end_page |
314 |
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1810450037031829504 |