Formation of joints in bedrock by moving glacial ice

Journal of Research of the U.S. Geological Survey



The orientation of joints in igneous and sedimentary rocks was measured at 21 localities in California, Maine, and New York to investigate the hypothesis that glaciation may open joints in bedrock. A summary of strikes of all joint sets shows the following pattern relative to the direction of glacial advance: two sets, thought to be extension joints, flank the direction of advance and are separated from it by about 10°; two sets, thought to be shear joints, flank the direction of advance by about 40°; and two sets, thought to be release joints, are about 70° to 80° from the direction of advance, or nearly perpendicular to the extension joints. An average of five joint sets, including three or four in this pattern, was found at each locality. The joints are believed to have been opened, in response to stress applied by the moving ice, along preexisting zones of weakness (potential regional joints) in the rock. Some new joints may have formed where no such zone was present near the position required for fracture under the applied stress. Additional investigation of the hypothesis is desirable because of its possible bearing on glacial erosion by quarrying, on interpretation of joint patterns in glaciated regions, and on the nature of aquifers in glaciated bedrock.

Publication type Article
Publication Subtype Journal Article
Title Formation of joints in bedrock by moving glacial ice
Series title Journal of Research of the U.S. Geological Survey
Volume 1
Issue 2
Year Published 1973
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 7 p.
First page 229
Last page 235
Country United States of America
State California, Maine, New York
Online Only (Y/N) N
Additional Online Files (Y/N) N
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