CATASTROPHIC GLACIER ADVANCES
Abstract
A theory is developed to explain catastrophic glacier advances, based on a previously developed glacier sliding theory (Weertman, 1957). It is found that catastrophic sliding is possible when the thickness of the water layer at the bottom of a glacier exceeds the size of the obstacles which normally control the velocity of sliding. The conditions which appear to be necessary for catastrophic advances to occur are: (1) the glacier should be long (10 - 30 km) and its bottom surface should be at the melting point; (2) the water at the glacier bed should flow as a sheet of water with only negligible flow in stream channels; (3) an above-average shear stress (of the order of 2 bar) should act at the bed. Such an abnormal stress could be produced by the arrival of large kinematic glacier waves; and (4) the glacier bed should be smoother with respect to large protuberances and obstacles than to small hindrances. The theory can be applied to explain the rapidly fluctuating velocity changes observed in ordinary glaciers. Kinematic water waves in the water layer at the bottom of a glacier can produce rapidly changing fluctuations in the surface velocity of the glacier. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1962
- Accession Number
- AD0292934
Entities
People
- Johannes Weertman
Organizations
- Cold Regions Research and Engineering Laboratory