Underlying the Arctic plains is a thick, unbroken layer of permafrost. Water that melts on top of the permafrost collects into what are called "thaw lakes".

These landforms result from thawing of ice-rich permafrost or the melting of snow and ice, but the frozen ground underneath prevents the water from draining away.

Water pools in a depression and its presence begins to further thaw the permafrost underneath and along the lake edges, gradually extending the lake.