Nivation is an intensive thermogenous process of rock's destruction acts near snow banks in spring and summer| it as widespread in mountains and high latitudes. The nivation results from the solar energy which causes sharp contrast in temperatures
of bare rock surface near the snow| surface under the snow and air near the surface. The intensity of nivation, the rate of rock's destruction is controlled by amplitude and frequency of the temperatures fluctuations within the active layer near the snow's
boundary, effective heat capacity and coefficient of thermal expansion. Being a thermogenous process the nivation acts not only near the snow banks but glaciers and icing as well. (Ed.).
Climatic relationships of permafrost zones in areas of low winter snow-cover
In areas with under 50cm snow cover in winter, the permafrost zones are defined by the freezing indices and thawing indices. The warmer boundary of the zone of continuous permafrost traverses the mean annual air temperature (MAAT). The boundary