ИСТИНА

Sporadic permafrost and seasonal ground freezing, various rocks and loose sediments, unsteady regional and local climatic features are typical for the subarctic mountainous massifs. These landscapes are sensitive to even slightest changes in the environment. Its impact focuses first of all on the smallest forms among which here cryogenic microrelief is most common. Our main aim is to reveal the space-time patterns of cryogenic microrelief development in combinations of natural conditions in the Subarctic mountains. Cryogenic microrelief is a complex of landforms (from tens of centimeters up to first meters in size) those appear due to alternate freezing and thawing of the soppy ground composed of fine and coarse material. Our research is proved by vast amount of field data gathered during 2006-2012 in 17 expeditions to the Russian North: the Khibini mountains in the Kola Peninsula, the Polar Ural and the mountains of Kamchatka. For the first time we have widely used grain-size and chemical analyses of ground samples, radiocarbon dating of the organic interlayers and the buried sod, large-scale mapping and profiling. A station for the solifluction rates measurement has been established in the Khibini in 2010. A bulk of morphometric data of the cryogenic forms’ features (length, width, height and composition of its elements) and the environmental conditions (altitude, angle and exposition of the sites) was processed and analyzed, typical limits for each parameter and each region are found. We consider, following A.L. Washborn, three main types cryogenic microforms in the Subarctic mountains due to its cells form and profile: isometric (polygons, circles, nets), linear (stripes) and stepped (steps, terraces). They are divided into subtypes, kinds and subkinds on morphologic, structural and compositional features, but are genetically common. They constantly transform in space and time because of the combinations of local conditions which determine the thermic regime of the ground. Each type and subtype of cryogenic microrelief develops through several stages. At the stage of growth the outward appearance and internal structure of the ground are noticeably changed. At the stage of stable functioning exterior and structure of the landforms are preserved, but often its height differences and seldom its size increase. At the stage of degradation the microforms are slowly destroyed losing at first its morphologic evidence and then its internal structure. The duration of each stage is from first decades up to several hundreds of years. They naturally replace each other in time, or evolve, and form the genetic sequences. The direction its evolution is defined by the combination of initial natural conditions. Then it depends on the self-development of forms due to local redistribution of temperatures and moistening in the ground. This secondary differentiation of local conditions causes the cyclic development of the cryogenic forms.