The closing of thermal contraction (ice-wedge) cracks at Garry Island, N.W.T., 150 km northwest of Inuvik, N.W.T., has been measured by means of gauge probes inserted into the cracks and by precise taping between bench marks across ice-wedge troughs. The results show that a simple elastic model fails to explain the time of cracking, the depth of cracking, the crack spacing, and the time of closing. The mean annual ice vein increment, at Garry Island, is probably less than 20% of the mean winter crack width. Thermal contraction cracks are of potential engineering interest, because they may affect underground cables, reservoirs, and other man-made structures.

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