ABSTRACT
Cryogenic patterned ground refers to the arrangement of stones or disturbances in the vegetation cover producing distinctive patterns resulting from convection cells in the active layer or seasonally frozen ground due to freezing and thawing. Sometimes, the sediment shows negligible sorting and the feature appears as a break in the vegetation cover. In other cases, there is obvious sorting of the finer material from the coarser rocks and pebbles. Obviously the first requirement is a period of freezing temperatures, diurnal or seasonal, resulting in freezing of at least part of the soil surface. Once segregation of the coarser clasts has taken place, the blocks forming the margins of the polygons act as drainage channels for the summer precipitation. Vegetation cover is very important since the patterned ground normally occurs in windswept locations. Climate and hydrology are the main controlling factors determining the processes involved, together with the presence or absence of a vegetation cover.
