Methodological basis of geocryology

The laws of dialectical materialism provide the starting point for the construction of scientific concepts in geocryology*. Thus it is the most general dialectical law on the evolutional character of quantitative changes

*The initiation of the development of the methodological basis as far as geocryology is concerned is associated mainly with V.A. Kudryavtsev's work.

and the spasmodic character of transition (at the particular stage) of quantity into quality, which has predetermined in essence the appearance and existence of geocryology itself. Actually the change of ground temperature in positive or negative direction (without going through 0°C) causes transformations only of the quantitative properties of the earth materials, with these materials continuing to belong to the same class of earth material. When the temperature passes through 0°C the phase transition of water into ice and of the earth material from the unfrozen state into the frozen one (and vice versa) occurs. With this there is a deep qualitative material transformation which manifests itself first of all in an essential difference of the soil or rock composition, structure, texture and most properties compared to those of the unfrozen and thawed materials. As this takes place a mineral (ice) is formed and specific new (cryogenic) materials appear, i.e. a quantitatively new geological object - the frozen soil or rock - is formed.

The correct understanding and interpretation of the negation of negation law, as applied to the process of the transition of the unfrozen sedimentary materials into the frozen state and then the subsequent thawing and transition into the thawed state, is of great interest for geocryology. The first negation of the unfrozen ground in this case consists not only in the transition of the sedimentary formations into the frozen state but also in an essential change of their granulometric, microaggregate and chemical mineral composition, structure, texture and properties. Therefore the second negation, i.e. the return of the frozen ground into the unfrozen state ('negation of negation' proper), will never lead this frozen ground to its original quality. That is the reason why researchers should distinguish not only the unfrozen (that is, never frozen) soils and rocks and the frozen ones, but also those which have been frozen in the past.

By and large the sedimentary formations in the permafrost follow complex evolutional paths never returning to the starting position, in accordance with the principle of indissolubility of unity and struggle of opposites. In this manner the law of the continuous development of the cryolitho-sphere must work in nature, i.e. of continuous progressive movement in a spiral in accordance with the general history of development of the lithosphere and of the whole Earth. From this follows the irreversibility of lithogenetic development in the Earth's history and the necessity to use principles of actualism and historical method simultaneously in the course of geocryological analysis.

The frozen earth materials are complex and rather dynamic natural objects formed in specific geosystems. The latter represent the multitude of natural components connected with each other in a certain order (typically, structure and properties) and making up the integral unit in the form of natural terrain complexes. It is natural that the approach to permafrost investigations should be systematic, complex, based on laws of universal and causal relationships between processes and phenomena, on continuity of development, on transformation of quantity into quality and other laws of dialectic materialism. The methodological importance of such an approach lies in the fact that the perennially frozen rocks are studied in relation to each element of the complex (system) individually and in their particular combination as a single whole. At the same time dependences are determined and particular and general principles are established. By the first is meant two way dependence, between two geocryological characteristics one of which is considered as a causative factor, the other one as an effect.

By general principle is meant the net result of the effect of all the natural factors typical of the given natural complex, on the formation of one of the geocryological characteristics expressed either by temperature regime of ground or by thickness or cryogenic structure of permafrost or by the particular type of seasonally and perennially frozen ground with its distinctive features.

Analysis and synthesis are the basis for the investigations of principles. The study of permafrost can be divided into a number of problems associated with the study of particular characteristics such as composition, structure, properties, thickness, temperature regime, etc. Each geocryological characteristic reflects the particular quality of an object and its association with other characteristics (properties, manifestations). By and large all the characteristics of the natural environment form the individual natural complex or geosystem. This association is complex and is individually inherent in each natural (including geocryological) characteristic. At the same time all geocryological characteristics are closely associated with each other. That is the reason why the dialectical approach (from complex to simple and then to complex again, from particular to general through analysis and then to general through synthesis, etc.) has become firmly established in geocryological investigations.

The process of cognition of natural geocryological systems is possible in the course of integrated geocryological surveying, revealing the dependencies and establishing experimentally principles of distribution and dynamics of various types of seasonally and perennially frozen ground and their inherent characteristics, by way of logic and mathematical modelling (based on experiment). A definition of survey was given by V.A. Kudryav-tsev in 1961. Permafrost (geocryological) survey represents the complex field, laboratory and office work aimed at the study of seasonally and perennially frozen ground and permafrost geological processes and phenomena, and the establishment of the principles in accordance with the existing natural conditions, their natural change during the Pleistocene - Holocene and under technological effects as well as the compilation of permafrost maps and predictions of permafrost occurrence. The main method of permafrost surveying is the key landscape method, the essence of which is the following: at the first stage the typological landscape regionalization (microregionaliz-ation) of a territory is carried out with respect to factors and conditions associated with the formation and existence of particular types of seasonally and perennially frozen ground. Then the key areas typical of the recognized types of landscape are selected as the basis of the landscape regionalization map. Particular and general geocryological principles, hydrogeocryological and engineering geocryological conditions, are studied within these key areas during the field periods by various methods and then the geocryological maps are compiled by way of extending the obtained principles over the types of landscape analogous to those studied within the key area and traced on the map of landscape régionalisation.

The study of the freezing conditions of a territory should be carried out taking into account the dynamics of the whole natural environment. Thus, for example, the formation, spatial and temporal change of seasonally and perennially frozen ground should be considered in connection with the general geological history of development of the territory in Late Cenozoic, i.e. with the history of the sedimentary strata and their particular facies with the history of development of topographic, hydrogeological and hydrologi-cal conditions, vegetation, climate, etc. The necessity for consideration of the dynamics of permafrost is one of the items of the geocryological survey. Reconstruction of the history of development of frozen ground in the Neogene and Pleistocene within the region under study and adjacent territories, is a logical completion of the study of dynamics.

The permafrost conditions change drastically in connection with inevitable disturbance of the natural conditions as a result of extensive economic development of an area. Therefore special work on prediction (i.e. expected change) of the permafrost conditions in the course of natural development as well as because of anthropogenic effects on the natural environment, are carried out in the course of geocryological surveys. Geocryological prediction and development of measures intended to initiate change of permafrost conditions, are carried out on the basis of the revealed particular and general principles of formation and development of the frozen ground as well as permafrost geological processes and phenomena.

A large complex of field, laboratory and office methods is used to study geocryological conditions and principles of their formation, to determine classificational features of frozen rocks, taliks, geocryological processes and phenomena. Along with general scientific methods being used in other sciences, geocryology has its own, specific methods allowing for the study of the principles of seasonally and perennially frozen ground and freezing-geological processes and phenomena and their development as well as their physical nature, at various levels of knowledge (from microstructure to macrostructure).

One of the main aspects of any science is correct relations between theory and practice in the course of cognition: from practice to theory and from theory to practice again. Geocryology was initiated by practice, i.e. in the practical needs of human engineering activity in the regions of frozen ground and in connection with prospecting and exploitation of deposits within the permafrost regions. Consideration of practical questions inevitably demanded a temporary distraction from practice, for the establishment of relationships and general laws of ground freezing, i.e. for the development of the theoretical basis of the study of geocryology. Theoretical constructions based on practice are verified, supported and gain new momentum for further development.

Thermal-physical, physico-chemical and mechanical processes in freezing, frozen and thawing ground and their manifestation in the permafrost regions

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