What happens to the soil when it freezes, then thaws

Regular annual freezing and thawing of permafrost soils can create very interesting geometric patterns - patterned soils. These can be polygons, circles, nets and stripes. They are usually observed in subglacial regions - for example, in Siberia, Canada, Alaska, Iceland, Greenland, Antarctica and the Andes.

The process of forming such ornaments has puzzled scientists for a long time, but the introduction of computer geological models over the past 20 years has allowed them to link the formation of these patterns with the phenomenon of soil swelling from frost — when wet, fine-grained and porous earth freezes.