Aufeis

an ice body that forms as a result of the layer-by-layer freezing of rivers or underground waters that flow onto the surface or into a cavity in rock as a result of the discharge of subterranean or surface water under pressure when river channels or water-bearing horizons freeze solid. A distinction is made among the surface-water form, the subterranean-water form, and mixed forms of Aufeis, depending on their origin.

Aufeis is most widespread in the region of permanently frozen rock, but it is also common in regions with deep seasonal freezing. The intensity of development of Aufeis formations depends on the reserves of subterranean water and the water supply of the preceding summer and on the depth to which the seasonally thawing layer freezes. The places of emergence of Aufeis are confined to sectors where river channels narrow sharply, and also to centers of subterranean water discharge. A distinction is made between dry Aufeis, which is formed by one-time water discharge, and wet Aufeis, which is covered with water that gradually flows onto the surface of the ice.

Aufeis ranges in area from tens and hundreds of square meters to hundreds of square kilometers and more. The largest areas of Aufeis are observed in Yakutia and the northeastern USSR. Perennial Aufeis, which thaws only partially during the summer, is found there. The total volume of Aufeis in the northeastern USSR is about 25 cu km, which is greater than the volume of all glaciers in that region. Aufeis plays a significant role in feeding rivers, especially in regions where snowfall is light and in regions where little precipitation falls in the early summer (Yakutia and Transbaikalia). It causes damage by covering over and destroying roads and by deforming buildings.