Marks and Forms on Glacier Beds: Formation and Classification

Abstract

Glacial erosion wears the bedrock grain by grain, that is it breaks free a multitude of little fragments. It also acts upon the bedrock to cause trains of concentric fractures and quarried surfaces. Since this type of erosion is selective in places of variable resistance, it brings about dug-out forms like grooved joints, or salient forms like veins carved out from up-stream down, it produces small-scale features like grooves or chattermark trains or, on a larger scale, acts upon rocky knobs to produce roches moutonnées; the latter, in spite of their dimensions, are subject to an action that can still affect every point simultaneously. Our objective is thus to present hierarchically the glacial forms left on the bedrock, along with the terminology that designates them. In Table I we give both English and French terminology, but it is not our purpose to make definite proposals for the few new terms in English.