Permafrost

Since its introduction, the definition of permafrost has rarely been discussed or reviewed. Recent decades have brought a series of significant, often interdisciplinary works on a periglacial zone and permafrost as well as their relation with other components of the environment, especially with glaciers. They show that, despite its unequivocal definition, the term has lost its sharpness and explicitness with regard to some aspects of research. The article presents a current state of understanding of permafrost phenomenon, regarding the use of the term permafrost, which means a physical state, not a material thing. Processes which it undergoes, that is exclusively aggradation and degradation, and also the possibility of its occurrence in glacial and periglacial environments of geographical space, where it covers over a quarter of land area on the Earth. (C) 2011 Elsevier B.V. All rights reserved.