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Extrusion Flow Demonstrated by Bore-Hole Deformation Measurements Over a Riegel, Storglaciären, Wweden
Journal of Glaciology (1987)
  • Roger LeB. Hooke, Stockholm University
  • Per Holmlund, Stockholm University
  • Neal R. Iverson, University of Minnesota – Twin Cities
Abstract
Inclinometry measurements in a 126 m bore hole slightly down-glacier from the crest of a riegel on Storglaciären showed what appears to be indisputable extrusion flow during the last 3 weeks of July 1984. The velocity at the bed was about five times that at the surface, and lay in a direction deviating 50‐60° from that at the surface. The increase in velocity with depth began more than 50 m above the bed. In August and the first half of September the flow returned nearly to “normal” with only a slight tendency toward extrusion. The flow in July appeared to be related to a period of large diurnal water-pressure variation and cavity opening at the bed up-glacier from the riegel. Decoupling of the ice from the bed on the lowest parts of the riegel may have permitted the extrusion. The return to more “normal” conditions in August appears to have been related to a decrease in ice flux over the riegel and a widening of the zone of decoupling.
Disciplines
Publication Date
1987
DOI
10.3198/1987JoG33-113-72-78
Publisher Statement
Copyright International Glaciological Society 1987. Posted with permission.
Citation Information
Roger LeB. Hooke, Per Holmlund and Neal R. Iverson. "Extrusion Flow Demonstrated by Bore-Hole Deformation Measurements Over a Riegel, Storglaciären, Wweden" Journal of Glaciology Vol. 33 Iss. 113 (1987) p. 72 - 78
Available at: http://works.bepress.com/neal-iverson/17/
Creative Commons license
Creative Commons License
This work is licensed under a Creative Commons CC_BY International License.