Classification and regionalization in the course of geocryological survey

Classifications in geocryology systematize research data and reflect cause and effect linkage (in some cases, time linkage) between phenomena and their characteristics, properties and processes.

In the late 1960s, V.A. Kudryavtsev and others had systematized and developed the main features of the classification of natural factors and permafrost for the purposes of geocryological survey and mapping on the basis of the theory of permafrost formation and development. The features were divided into three groups. The natural factors responsible for the conditions of formation of seasonally and perennially frozen ground constituted the first group. These are geological and geomorphological struc tures of the area, lithologic-genetic peculiarities of the freezing deposits, and hydrogeological, geobotanic and climatic conditions.

The second group of features characterizes heat exchange at the ground surface and inside the ground unit whereby the permafrost is classified with respect to the latitude and climatic continentality; to the mean annual temperatures of ground and duration of temperature fluctuations at the surface with which the developed thickness of permafrost is associated; and to the value of ice content and cryogenic structure.

The features by which permafrost is subdivided with respect to its specific peculiarities constitute the third group. These are the distribution, structure and particular geocryological characteristics. For example, the permafrost is subdivided with respect to its distribution into continuous permafrost, discontinuous permafrost, permafrost islands and sporadic permafrost; with respect to mode of occurrence in profiles, merging into the seasonally thawed layer, or occurring at great depth from the surface and being separated from the seasonally frozen layer as relict frozen strata etc.; with respect to dynamics into degrading across the whole thickness, or with aggradation from the top and degradation from the bottom; aggradation across the whole thickness, etc.

Classification features of all three groups are mutually related: the features of the first group predetermine the features of the second group, while taken together, they predetermine the features of the third group. The features of the first group and partly of the second group are used for landscape regionalization of the area in the course of geocryological research; the features of the second group and of the third (partly of the first) are used to compile geocryological maps. When compiling maps for the particular regions researchers select from the general system of features those which are typical, are responsible for their peculiarities and are adequate for the aims of the investigations. With respect to these features the regional permafrost classifications are drawn up and in accordance with them legends for the maps are worked out. A good example of such a classification is the regional classification of frozen Quaternary deposits of the north of Western Siberia (Table 16.1).

Of great scientific and practical importance are classifications of frozen ground with respect to cryolithogenetic features as a guide to the ground composition, structure and properties. In this regard the general tabulation for subdivision of cryolithogenesis put forward by the author has considerable promise. In this tabulation the physical-geographical conditions of the permafrost formation (radiation-thermal and water balances), tectonic, geo-logic-geomorphological conditions, character of seasonal or perennial

Table 16.1. Detail of the engineering-geocryological classification of Quaternary permafrost: the example of Western Siberian region

Type (with Subclasses (with respect to respect to

Table 16.1. Detail of the engineering-geocryological classification of Quaternary permafrost: the example of Western Siberian region

Type (with Subclasses (with respect to respect to

occurrence in

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