Process: Frost Heave
The upwards dislocation of soil and rocks by the freezing and expansion of soil water.
Frost Pull – This occurs when ice creeps downwards from the surface – as the active layer starts to refreeze, ice crystals begin to develop, which increases the volume of the soil and causes an upwards expansion on the soil surface and cause the stone to be pulled into a vertical inclination. Melting in the following spring causes water to flow through the soil and transport fine sediment below the stone which prevents the stone falling back.
Frost Push – Occurs when cold penetrates into the ground and large stones become cold more rapidly that the soil, as stones have a lower thermal heat capacity, meaning that the soil immediately beneath the stone is likely to freeze and expand before any other material, pushing up the stones until they reach the surface.
Landform: Stone Polygons and Patterned Ground (as seen above)
Frozen ground cracks and forms patterns on the ground in which loose stones fall into the cracks to highlight the outlines.
Stone polygons tend to form on shallower slopes.
Frost heave thrusts larger particles upwards and smaller particles will probably be removed by wind or meltwater, leaving a concentration of larger stones lying on top of the ice wedges.
When there is a steep incline the stones will slide down the hill meaning the polygons become distorted and become stone stripes.