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freezing of deposits and forms of lithogenetic process are taken into account. This schematic allows classification of frozen ground as a function of particular lithogenetic processes and gives a lead to the systematization of cryogenic rocks not only of the Earth but also within the Solar system as a whole (10).

Classifications of frozen rocks put forward by I.Ya. Baranov, Ye.M. Katasonov, B. I. Vtyurin and Sh. Sh. Gasanov are united by a common genetic approach to subdivision of the frozen layers with respect to the type of their freezing (epigenetic or syngenetic). Classifications put forward by V. A. Zubakov and I.D. Danilov use, respectively, formations and facies as approaches to the subdivision of the frozen materials. A.I. Popov in his classification considers the frozen materials to be a result of cryolithogen-esis. He subdivided them with respect to the content of ice as a mineral. There exist now a great number of classifications of frozen materials in which they are subdivided with regard to particular gradations of one or another characteristic (for example, mean annual temperature, thickness and ice content), as applied to the problems under investigation. The indicators can be genetic, spatial, temporal or quantitative.

Aligning of the classification criteria in a ranking scale is carried out every time on the basis of establishment of cause and effect linkage: to identify the first (lower) ranks we should select the features amost commonly associated with features of the next higher subdivision. These rules of multistep classifications (by the greater number of features) should be abided by from step to step. Each step can be a simple one-row classification within which the recognized subdivisions of the subject are equal in rank. Such particular classifications form the basis for the integrated Geocryological Map of the former USSR at the 1:2 500000 scale edited by the author.

When using the relatively independent groups of features (for example, regional and zonal) cross matrix classifications are often constructed.

Regionalization in the course of geocryological investigations is closely related to the construction and usage of the classifications. At the present time three types of regionalization, typological, individual and individual-typological, are widely used. Typological regionalization refers to ground types or landscape types similar in one or a few features and selected for the purpose of regionalization, which are set aside and separated from land without such features (or particular gradations of indicators). In the course of individual regionalization the adjacent units and regions being relatively similar as far as some fundamental feature is concerned, are unified and separated from the parts without this feature. In the course of individual-typological regionalization the units of territory are first isolated individually with respect to one important feature and then are subdivided into types of ground each having common features.

Terrain regionalization with respect to the end use is multifunctional in geocryology. Regionalization is performed in the first place to study and analyze the variability of natural complexes (landscape regionalization) in which the perennially frozen ground exists; secondly to follow spatial variability of geocryological characteristics or to reveal common geocryological features (geocryological regionalization proper); and thirdly to assess the area for the solution of practical problems. And if the selection of regionalization features for the first purpose is conditioned by structural-geological and geographical features and by geocryological characteristics, the selection of features for the assessment regionalization is defined by the specific engineering use of the geocryological environment (by types of economic development) and by the particular engineering-geocryological conditions. In all cases certain requirements and limitations are imposed on the selection of regionalization features and their gradations by the scale of map.

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