Geocryology (the study of frozen soils) is a natural and historical science and a branch of geology, concerned with the laws of the formation and the evolution in time and space of frozen ground, its composition, cryogenic structure and properties, and with cryogeological processes and phenomena. The frozen ground may be hundreds of meters thick (up to 1500 m) in the region comprising the freezing zone of the lithosphere characterized by freezing temperatures (to — 15°C) and inclusions of ice or ice crystals.

As any other branch of knowledge, geocryology has resulted from practical needs, and its coming into being has reflected the economic development of huge permafrost tracts, which include currently 25% of all land on our planet and some 50% of the territory of the former USSR.

The subject of geocryology is now well-defined, as are a range of its basic problems, its practical and scientific significance; techniques and procedures for special geocryological researches have evolved; with its major fields and trends established, the prospects of geocryology gaining both in science and in application have proved very promising. Vladimir I. Vernadskiy has noted earlier that it is the limits of cooling below the ground surface which define a task relating to the solution of problems which are all of great scientific and practical importance.

The topic of geocryology is frozen ground, including underground ice and snow accumulations. According to the views of A.B. Dobrovolskiy, V.I. Vernadskiy and P.I. Koloskov, frozen ground occurs in the cryosphere, which is a thermodynamic envelope of the Earth where ice, water and vapour can exist simultaneously under negative temperatures. Permafrost is a natural geological formation noted for its distinctive laws of genesis, existence, evolution and distribution on the planet. Looking to outer space, most planets of the Solar system and other celestial bodies appear to be cryogenic, i.e. to be noted for permafrost developed on them. In other words, our perspective extends from the cryology of the Earth to that of the planets or Universe, cosmic cryology.

Several works of generalization have been written on the fundamentals of geocryology. General Frozen Ground Studies by M.I. Sumgin, S.P. Kachurin, N.I. Tolstikhin and V.P. Tumel, came in 1940, and in 1959 Fundamentals of Geocryology, the magnum opus, put out by the Institute of Frozen Ground Studies. The first edition of the textbook General Frozen Ground Studies was printed in 1967, its second edition in 1978, and in 1981 came Frozen Ground Studies (Concise Course) prepared and edited by V.A. Kudryavtsev. General Frozen Ground Studies edited by P.I. Mel'nikov and N.I. Tolstikhin appeared in 1974. All these books have proved very important in laying the foundations of geocryology; now they are rarities, and what is more, many of their chapters are in need of considerable reworking due to substantial advances made recently in formulating the theoretical and applied (engineering) fundamentals of geocryology.

The present textbook, based on the latest advances in science and practice, expounds in condensed form the fundamentals of dynamic, lithogenic, regional, historical and engineering geocryology. It is designed for students and lecturers in geocryology at universities (the 'Engineering geology and groundwater hydrogeology' specialization), and in geological exploration, mining, oil and gas, building and transport, at institutions of higher education. There is no doubt it will be useful for a wide range of geologists in research and commercial bodies, and for many technicians in design and survey, building and mining establishments engaged in exploration and economic development of the permafrost regions.

Colleagues from the Department of Geocryology in the Geology Faculty at Moscow State University participated in compiling the textbook. Some chapters and subsections were written in collaboration with V.Ye. Afanasenko(Ch. 13),L.S. Garaguliya (Introduction, #5; Ch. 16,#l-3;Ch. 19, #2), I.D. Danilov(Ch.9), K.A. Kondrat'yeva(Ch. 14,#3;Ch. 15,#l,2;Ch. 16, #1 and 4), S.Yu. Parmuzin (Ch. 17-19). Participating in writing individual subsections were Ye.N. Dunayeva (Ch. 15, #3), V.Ye. Romanovskiy (Ch. 1 #4 and 5; Ch. 10, #1), S.F. Khrutskiy (Ch. 10, #3; Ch. 12, #3); Ye.M. Chuvilin (Ch. 8, #4; Ch. 9, #3).

Ye. M. Chuvilin was responsible for preparing the manuscript for publication. Assisting him at all stages of its preparation were T.N. Kosatkova, L.A. Nikulicheva, O.N. Patrik.

The author would like to thank all these contributors, especially K.A. Kondrat'yeva who has read the final manuscript, for their invaluable help.

Chapter 2 was translated by A.D. Anikin. The Preface and Chapters 3 -11 were translated by L.A. Kholdobayeva and A.K. Stroganov. The Introduction, Chapter 1 and Chapters 12-19 were translated by N.B. Guseva.

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