Influence of rock jointing on the asymmetric form of the Ptarmigan Glacier valley, south-eastern Alaska

Abstract

Jointing of rocks is concluded to be the main factor affecting the asymmetric form of the Ptarmigan Glacier valley. Fault lines control the general direction of the valley. In the paper the general influence of joints on the valley forms is also discussed. The most suitable conditions for the formation of a symmetric U-shaped glacial valley exist when the dipping of the predominant joint sets is close 0°, 45° or 90° and the strike is parallel to the axis of the valley.