| Abstract: | 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. |
| Genre: | Article |
| ProdID: | 70031262 |
| Citation Author: | Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Moore, P. L.; Jackson, M.; Lappegard, G.; Kohler, J. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 340 |
| Citation Issue: | 182 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Journal of Glaciology |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 18 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation; 2007; Article; Journal; Journal of Glaciology; Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Moore, P. L.; Jackson, M.; Lappegard, G.; Kohler, J. |
| Citation Start Page: | 323 |
| Citation Volume: | 53 |
| Citation Year: | 2007 |
| Type: | citation/reference |
| Text: | Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation; 2007; Article; Journal; Journal of Glaciology; Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Moore, P. L.; Jackson, M.; Lappegard, G.; Kohler, J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Mon, 1 Jan 2007 00:00 -0600 |
| Publisher: | |
