From history of studying of permafrost in the South-East of Western Siberia, its types and influence on relief forming
The permafrost area covers about 70 % of territory of Russia and the seasonal frost area comprises about 25-30 %. The permafrost is also widespread in the South-East of the West Siberian plain within the taiga and subtaiga zones of the Tomsk oblast', where three types of permafrost are identified: seasonal, sporadic island formation and relict. Certain cryogenic processes develop in each type of permafrost. Veined and polygonal relief, thermokarst are associated with relict permafrost, palsas (palsa) are formed in the areas with island permafrost, heaving of soils and frost cracking occur in areas with seasonal permafrost. The immediate proximity to the southern border of the cryolithozone, the presence in the North and North-East of the region of deep-lying relic frozen rocks, and long (up to 5-6 months) and deep (up to 2-3.5 m) seasonal freezing of rocks are features of modern geocryological situation in the territory of Tomsk oblast'. This article briefly considers the history of the discovery of the relic permafrost in Western Siberia by A.A. Zemtsov, who was Professor of the Tomsk state University (1957); in the article also the area of permafrost in the Tomsk oblast', its depth and thickness are given and the influence of cryogenic processes on the relief is described. The paper characterizes natural factors of seasonal permafrost development such as dispersion and humidity, average annual and minimum temperatures of soil and air, depth of freezing and other factors. Cryogenic processes developing in seasonal and relic permafrost of Tomsk oblast' are insufficiently studied. The authors consider a genetic series of cryogenic processes developing in the Tomsk oblast' based on field research and analysis of literature sources. One of the most dangerous processes is frost heaving in dispersive grounds. The data on the distribution of relic permafrost should be considered into account when designing and drilling exploratory wells for oil, gas and groundwater, construction of roads, pipelines, buildings and other facilities