Document Type
Article
Publication Title
Journal of Glaciology
Publisher
International Glaciological Society
Publication Date
1998
Abstract
Values of the strain-rate tensor r epresented at a 20 m length scale a re found to explain the pattern and orientation of crevasses in a 0.13 km2 reach of Worthington Glacier, Alaska, U.S.A. The flow field of the reach is constructed from surveyed displacements of 110 markers spaced 20-30 m apart. A velocity gradient method is then used to calculate values of the principal strain-rate axes at the nodes of a 20 m x 20 m orthogonal grid. Crevasses in the study reach are of two types, splaying and transverse, and are everywhere normal to the trajectories of greatest (most tensile) principal strain rate. Splaying crevasses exist where the longitudinal strain rate (Ex ) is greater than 0 and transverse crevasses are present under longitudinally extending flow (i. e. Ex greater than 0). The orientation of crevasses changes in the down-glacier direction, but the calculated rotation by the flow field does not account for this change in orientation. Observations suggest that individual crevasses represent local values of the regional flow field and are transient on the time-scale of 1-2 years; they are not persistent features that a re translated and rotated by flow. Crevasse patterns are thus found to be a useful tool for mapping the strain-rate ten or in this reach of a temperate valley glacier.
Rights
© International Glaciological Society
Comments
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