Ground Contraction: The Key Facts

Process: Ground Contraction
Permafrost contracts in extremely low temperatures, resulting in cracks developing.
Landform: Ice Wedge Polygons         
– Permafrost contracts, creating cracks
– During summer, meltwater flows into these cracks and fills them up
– When it refreezes in the winter, the water expands by 9%, making the crack wider
– This process is repeated and the crack widens
– The ice expands which pushes the surface upwards creating bulges
– Over a period of hundreds of years the ice wedge polygon can become at least 1m wide and 2-3m deep
– The narrow layers of additional ice are called foliations

 

ice_wedge

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