Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation
To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m × 1.6 m × 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the be...
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ftiowastateuniv:oai:lib.dr.iastate.edu:ge_at_pubs-1143 2023-05-15T16:21:55+02:00 Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation Iverson, Neal R. Hooyer, Thomas S. Fischer, Urs H. Cohen, Denis Moore, Peter L. Jackson, M. Lappegard, G. Kohler, J. 2007-07-01T07:00:00Z application/pdf https://lib.dr.iastate.edu/ge_at_pubs/144 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1143&context=ge_at_pubs en eng Iowa State University Digital Repository https://lib.dr.iastate.edu/ge_at_pubs/144 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1143&context=ge_at_pubs Creative Commons Attribution license. CC-BY Geological and Atmospheric Sciences Publications Geomorphology Glaciology Sedimentology text 2007 ftiowastateuniv 2021-08-28T22:47:13Z To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m × 1.6 m × 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7–12 days, the glacier regelated downward into the prism to depths of 50– 80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of sustained high pore water pressure (70–100% of overburden), ice commonly slipped over the prism, due to a water layer at the prism surface. Deformation of the prism was activated when this layer thinned to a sub-millimeter thickness. Shear strain in the till was pervasive and decreased with depth. A model of slip by ploughing of ice-infiltrated till across the prism surface accounts for the slip that occurred when effective pressure was sufficiently low or high. Slip at low effective pressures resulted from water-layer thickening that increased non-linearly with decreasing effective pressure. If sufficiently widespread, such slip over soft glacier beds, which involves no viscous deformation resistance, may instigate abrupt increases in glacier velocity. Text glacier Digital Repository @ Iowa State University Engabreen ENVELOPE(13.771,13.771,66.682,66.682) Norway |
institution |
Open Polar |
collection |
Digital Repository @ Iowa State University |
op_collection_id |
ftiowastateuniv |
language |
English |
topic |
Geomorphology Glaciology Sedimentology |
spellingShingle |
Geomorphology Glaciology Sedimentology Iverson, Neal R. Hooyer, Thomas S. Fischer, Urs H. Cohen, Denis Moore, Peter L. Jackson, M. Lappegard, G. Kohler, J. Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
topic_facet |
Geomorphology Glaciology Sedimentology |
description |
To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m × 1.6 m × 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7–12 days, the glacier regelated downward into the prism to depths of 50– 80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of sustained high pore water pressure (70–100% of overburden), ice commonly slipped over the prism, due to a water layer at the prism surface. Deformation of the prism was activated when this layer thinned to a sub-millimeter thickness. Shear strain in the till was pervasive and decreased with depth. A model of slip by ploughing of ice-infiltrated till across the prism surface accounts for the slip that occurred when effective pressure was sufficiently low or high. Slip at low effective pressures resulted from water-layer thickening that increased non-linearly with decreasing effective pressure. If sufficiently widespread, such slip over soft glacier beds, which involves no viscous deformation resistance, may instigate abrupt increases in glacier velocity. |
format |
Text |
author |
Iverson, Neal R. Hooyer, Thomas S. Fischer, Urs H. Cohen, Denis Moore, Peter L. Jackson, M. Lappegard, G. Kohler, J. |
author_facet |
Iverson, Neal R. Hooyer, Thomas S. Fischer, Urs H. Cohen, Denis Moore, Peter L. Jackson, M. Lappegard, G. Kohler, J. |
author_sort |
Iverson, Neal R. |
title |
Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
title_short |
Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
title_full |
Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
title_fullStr |
Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
title_full_unstemmed |
Soft-bed experiments beneath Engabreen, Norway: regelation infiltration, basal slip and bed deformation |
title_sort |
soft-bed experiments beneath engabreen, norway: regelation infiltration, basal slip and bed deformation |
publisher |
Iowa State University Digital Repository |
publishDate |
2007 |
url |
https://lib.dr.iastate.edu/ge_at_pubs/144 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1143&context=ge_at_pubs |
long_lat |
ENVELOPE(13.771,13.771,66.682,66.682) |
geographic |
Engabreen Norway |
geographic_facet |
Engabreen Norway |
genre |
glacier |
genre_facet |
glacier |
op_source |
Geological and Atmospheric Sciences Publications |
op_relation |
https://lib.dr.iastate.edu/ge_at_pubs/144 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1143&context=ge_at_pubs |
op_rights |
Creative Commons Attribution license. |
op_rightsnorm |
CC-BY |
_version_ |
1766009891081682944 |