Experiments Relating to the Fracture of Bedrock at the Ice-Rock Interface

• Published in: Journal of Glaciology
• Main Author: Smith, Jennifer M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1984
• Subjects: Earth-Surface Processes; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000008583; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000008583

Abstract MacClintock (1953) has suggested that arcuate features formed on glass by the impression of steel ball bearings may be analogous to crescentic gouges observed on formerly glaciated rock surfaces. He noted that cracks, convex in the direction of movement, are formed as bearings roll over a glass surface but not as they slide over it. MacClintock therefore proposed that the similarly orientated crescentic gouges may owe their origin to abrading clasts rolling along a glacier bed. This note describes simple experiments designed to test this view by generating friction cracks artificially. Cracks convex and concave in the direction of movement were produced by a non-rolling bearing — a result apparently incompatible with MacClintock’s proposal. It is suggested that the orientation of such cracks is less dependent on bearing rotation and more the result of pressure variation. Cracks analogous to crescentic gouges may form as a result of unloading.