Ice-Wedge Cracks, Garry Island, Northwest Territories

Abstract

Observations made on winter ice-wedge cracks at Garry Island, N.W.T., for the 1967–73 period show that cracking tends to occur between mid-January and mid-March. On the average, nearly 40% of the ice wedges crack in any given year. The crack frequency varies inversely with snow depth. Medium sized ice wedges, about 1 m wide, crack more often than smaller or larger wedges, ice wedges crack preferentially near the center and often year after year at nearly the same place. The cracks average about 1 cm wide at the surface and taper downwards to depths which may exceed 5 m. The cracks partially close in spring before a new ice veinlet forms in them. Evidence provided by multiple wedges suggests that cracking may be initiated at times within the wedge rather than at the ground surface, and thus the cracks propagate both upwards and downwards.