5 - THE FORMS OF THE GROUND SURFACE 1: SLOPES AND SUBSIDENCES

Summary

Freezing and thawing and displacements of the ground

The thermodynamic and mechanical properties of freezing soils and rocks find expression in the appearance of the natural terrain. For over a century textbooks have described characteristic features of the ground surface associated with cold climates. Yet to this day there are features whose precise origin remains in doubt. Shaping of the ground surface by running water, the erosive effects of wind, or the instability of sloping surfaces induced by changing moisture or other conditions are common to temperate and cold regions. But those terrain forms exclusively associated with cold climates are of unusual interest and may be highly significant indicators of the special properties of freezing soils.

The development of slopes is, in the simplest view, a consequence of gravitational forces. The same applies to the subsidences of the ground which follow the thawing of excess ice. Such movements are the topics of this chapter. In the following chapter a variety of phenomena associated with essentially level ground in cold regions are considered.

Instability of soil on slopes: overview

The term solifluction has been used to describe many kinds of downslope soil movement in cold climates. It has also been applied to forms, superficially similar, in warm regions.