ABSTRACT

In areas underlain by permafrost, the freezing and thawing of the active layer can cause pressures to develop because of the phase change between water and ice, resulting in volume changes and churning movements. The permafrost table restricts water drainage, thus making the finer-grained soil more susceptible to mass wasting, and can result in detachment of the layers above the thawing front or permafrost table in spring and summer. Any large rocks anchored in the underlying permafrost tend to impede these downslope movements. This chapter examines three main types of mass wasting and how they affect movement of fine-grained material down slopes in cold climates, viz., slow flows, rapid flows, and slides. Slides are cases where the ground moves along a definite plane over a stationary surface. In flows, the surface soil moves fastest, with decreasing movement with depth until at greater depth, no movement occurs. Intermediate forms also occur and are dealt with under a separate heading.