Permafrost, Patterned ground

Intense seasonal frost action, repeated freezing and thawing throughout the year, produces small-scale patterned ground. Repetitive freezing and thawing tends to stir and sort granular sediments, thus forming circles, stone nets, and polygons a few centimetres to 6 metres in diameter. The coarse cobbles and boulders form the outside of the ring and the finer sediments