Thermokarst within the territory of the U.S.S.R.
DOI:
https://doi.org/10.26485/BP/1962/11/6Keywords:
ground-ice, zones of thermokarst development, degradation of permafrostAbstract
Thermokarst is a widespread natural phenomenon in permafrost regions; outside these areas there is no thermokarst. The presence of ground-ice near the surface is necessary for the development of thermokarst. The main cause of its origin lies in changes of the heat exchange conditions in the upper layers of deposits, leading to the melting of the ground-ice. Alterations in the heat exchange conditions within the layer of seasonal thermal fluctuations (i.e. in a layer up to 15-20 m depth) depend, in different geographical regions on many reasons, and not climatic changes alone.
Thermokarst is not a variety of karst, but an entirely independent natural phenomenon. Different types of thermokarst formations correspond to different genetic types of ground-ice; nevertheless in many cases the forms produced are similar in appearance. The process of thermokarst development is influenced by the geological structure, the facial differences of the deposits and the geomorphic conditions prevailing in any particular area.
The similarity of thermokarst settling features causes difficulties in ascertaining the genesis of the individual forms as well as in their classification. Thus, in studying the thermokarst phenomenon it is necessary to apply various methods of both field and laboratory investigations.
Like many other geologo-geographical phenomena thermokarst is usually zonal. On the basis on data derived from the literature three main zones of thermokarst development may be roughly distinguished in the territory of the USSR, though no clear boundary can be drawn between these zones. The history of thermokarst development is closely related to the aggradation. of permafrost during the Quaternary period and, in a still larger measure, to the process of its degradation.
The historical period of the increasing influence of human activities upon the natural conditions of the environment is especially significant and promotes a further development of the phenomenon. Thermokarst affects, in its turn, the economical and industrial activities of men thereby compelling us to undertake appropriate measures in order to control the disastrous effects of this phenomenon.
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