Geotectonics has a special place among the geological dis­ ciplines. In addition to ideas based on firmly established facts that constitute lasting scientific values, geotectonics, as a generalizing branch of geology, embraces broad con­ structions that link the planet's deep interior with its sur­ face and are largely of a hypothetical character. The inter­ pretation of the most general matters of the structure and evolution of the globe varies not only from one generation of geologists to another, but even within one generation. The interpretation depends not only, and not so much, on the state of geological knowledge, as on the progress of the related sciences of geophysics and geochemistry. In trying to discover the deep-lying causes of tectonic processes, geotectonics has to unite the results of all the Earth sci­ ences, converting itself to some extent from a purely geologi­ cal science into a general physical geographic or geonomic science. The fluidity of the general ideas andthe need for joint consideration of the geological, geophysical, and geochemi­ cal data to substantiate these ideas are the main difficulties facing the author of a textbook on geotectonics. There is undoubtedly, however, a need for a manual of this kind, particularly now when the literature on the various problems of geotectonics has grown so great and so varied in content that it is very difficult for the experienced researcher, let alone the student, to find his way.