Term
Active layer
The ground above permafrost that thaws in summer and freezes again in winter. Its thickness changes with local climate, vegetation and soil. Seasonal thaw of this layer does not necessarily mean that the underlying permafrost has disappeared.
What to look for
Patterned ground in Alaska's Noatak region. The active layer above permafrost thaws and refreezes seasonally; surface patterns show freezing processes, but active-layer depth needs field measurements.
Related labs
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