A principle of particle segregation by freezing is presented. It is demonstrated experimentally by means of a transparent freezing cabinet in which a sample of distilled water freezes from the bottom upward. In this way the freezing front line travels vertically and the particles are carried against gravity. By use of the same material with different shapes (glass beads and broken quartz or glass) it is demonstrated that an important factor in particle migration is the shape of the particle or its contact area with the interface. Other materials with different shapes and sizes were tested. The other important factors are particle size and rate of freezing. Fine particles migrate under a wide range of rates of freezing; coarser particles migrate at slower and narrower ranges of rates of freezing. It is suggested that, for determining frost behavior of soils in permafrost regions, freezing from the bottom upward is a more reliable test than freezing from the top down. Freezing from the bottom more closely approximates freezing of the active layer above permafrost; also friction with the cylinder testing wall is eliminated. The implication of this principle in engineering and studies of soil genesis in cold regions is emphasized.

Laboratory experiments that subjected soil to repeated freeze-thaw cycles in an inclined container revealed every process of solifluction, especially of frost creep. Multiple slope-angle effects on the amount of particle movement on the soil surface in every cycle are interpreted by several characteristic processes of frost creep. Gelifluction was found to occur in thicker layers of soil, owing to the excess water retained in soil after thawing. For further development of the problem, a similarity law for the model experiment was derived from thermal considerations.

If a hetrogeneous mixture of particles of various sizes is frozen and thawed repeatedly, the particles are sorted into relatively uniformn groups by size. The movement of particles depends on the amount of water between the ice-water interface and the particle, the rate of freezing, the distribution of the particles by size, and the orientation of the freeze-thaw plane.

This is one of a series of reports of work on USA CREEL sttbtask 5010. 031,41, Field and laboratory study of patterned ground.

There are problems in determining the amount of precipitation at a given site in mountain permafrost areas, because snow can be redistributed by wind or avalanches. Both snow and rain greatly affect permafrost distribution. Surface soil conditions also affect permafrost distribution. Dry blocky surfaces, peaty soils and soils with a thick organic mat tend to favour permafrost development. Active layers are deepest on dry mineral soils at low latitudes. Moist soils have thin active layers which exhibit the zero curtain effect during freezing and thawing. Meteoric H2O enters permafrost in response to thermal gradients. The H2O content may reach 80% by volume in its upper layers in some rock glaciers. In Kazakhstan a perched water table occurs above the thawing front in the active layer and provides a reliable supply of water to plants, so that the permafrost lands have a lush meadow tundra in summer. The physical and chemical properties of the discharge from mountain permafrost areas can be used to differentiate it from glacial discharge and groundwater. There is an antipathetic relationship between the lower limit of permafrost and the equilibrium line on glaciers. Gorbunov's Continentality Index is the only system for classifying the climate of mountain permafrost areas that indicates their great climatic variability.