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Science 4 July 2003:
Vol. 301. no. 5629, pp. 81 - 84
DOI: 10.1126/science.1083086
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Reports

Effects of Basal Debris on Glacier Flow

Neal R. Iverson,1* Denis Cohen,2 Thomas S. Hooyer,3 Urs H. Fischer,4 Miriam Jackson,5 Peter L. Moore,1 Gaute Lappegard,6 Jack Kohler7

Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance.

1 Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA. 2 Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA. 3 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Road, Madison, WI 53705, USA. 4 Laboratory of Hydraulics, Hydrology and Glaciology, ETH-Zentrum, CH-8092 Zürich, Switzerland. 5 Norwegian Water Resources and Energy Directorate, Middelthuns Gate 29, Post Office Box 5091, N-0301 Oslo, Norway. 6 Department of Geography, University of Oslo, Post Office Box 1042, N-0316 Oslo, Norway. 7 Norwegian Polar Institute, Polar Environmental Center, N-9296 Troms{phi}, Norway.

* To whom correspondence should be addressed. E-mail: niverson{at}iastate.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Subglacial bedrock welding associated with glacial earthquakes.
M. Bestmann, A.H.N. Rice, F. Langenhorst, B. Grasemann, and F. Heidelbach (2006)
Journal of the Geological Society 163, 417-420
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