Thrust plates of sediment at the snout of Aktineq Glacier (B17) 1
This image shows the ridge formed by a thrust fault, which is marked by deformed, bedded sand in the snout area of Aktineq Glacier (B17). The photo was taken in July 1977 with Dr. R. A. Klassen, Geological Survey of Canada (former graduate student at University of Illinois) for scale. Images 0042, 0043, 0045, and 0046 are of the same structure. The bed of sediment is sand or sandy bedrock that was frozen on to the base of the glacier and then thrust to the surface to stand almost vertically in the snout area, complete with distorted original bedding. The view is on top of the glacier, and the sediment is about 200 feet above the base of the glacier. The images show the edges of a ridge that have been cut through by a small glacier surface stream. The ridge is cored by the thrust sediment, which insulated the adjacent glacier ice as it melted out. As the clean ice surface adjacent to the sediment was lowered by melting, the thrust body and its adjoining, protected ice melted (lowered) much more slowly, forming the ridge. Image 0041 is of a similar phenomenon, but on a much smaller scale. Any sediment that comes to the surface as a result of melting in the snout areas of these glaciers stands as a bump, cone, or ridge because of the retarding effect on melting rates of the unfrozen sediment, which spreads over adjacent ice.
Updated 03/30/2010 AW