Classification of processes and phenomena

Exogenous geological processes and phenomena in the permafrost regions are often referred to as cryogenic (frozen ground) geological processes and phenomena. They are due to the development of the thermalphysical, physico-chemical and mechanical processes that occur in freezing, frozen and thawing soils, which were considered in the previous chapters. The specific features of exogenous geological processes in the permafrost zone are determined by the cyclic recurrence of freezing and thawing, cooling and heating, by the properties of frozen, perennially frozen and thawing soils, by the variability with time of ground stresses etc. These lead to the different cryogenic phenomena (formations) that contribute to the geological structure of loose Quaternary deposits and manifest themselves in the topography and micro-terrain within the area of permafrost as well as in the area of deep seasonal freezing. With regard to the basic agencies of the environment which are the driving forces for the processes and phenomena, all the exogenous processes in the cryolithic (permafrost) zone may be subdivided into three major groups (Table 5.1).

The first group comprises the cryogenic processes proper (frozen ground geologic processes) caused by seasonal and long-term variations of heat and mass exchange over the ground surface and in the underlying materials.