Abstract
AbstractCavity development in ice‐rich permafrost at Pangnirtung followed a large rainstorm and runoff event in 1984. The cavities evolved along permeable zones in sediments containing segregated ice lenses. Cavities promoted subsurface flow and incremental collapse of the ground surface. Once formed, cavities remained relatively stable where they were free to drain, and where the enclosing ground remained frozen and rigid support was provided. Some cavities closed by infilling with sediment or freezing water, or by deformation of the surrounding frozen ground. Other cavities were enlarged by thermo‐erosional piping, a process involving both thermal and mechanical erosion of frozen ground together with sufficiently rapid throughflow to prevent refreezing.A classification of cavities in permafrost permits qualitative appraisal of their stability with respect to the depth of zero annual temperature change and the degree of natural arching support. Assessment based on elastic plate theory indicates that seasonal temperature changes are important factors in destabilizing near‐surface cavities.
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