ABSTRACT

In all areas subject to freezing and thawing, the rocks exposed at the surface will be subjected to additional stresses by the extreme temperature changes (diurnal and seasonal) that occur in these places. The main source of blocks of rock is by detachment from bedrock. The concept of water penetrating cracks and developing enough force during freezing in an unconfined space to break rocks apart has been challenged by several authors. The nature of the rock has a great effect on the rates of production of blocks in a given permafrost climate. The soluble salts produced by chemical weathering are mainly removed by the surface runoff or in the water percolating down to the water table in humid regions. Block fields are relatively rare in young, heavily glaciated mountains such as the Rockies, but are more common in unglaciated areas and on nunataks, e.g., Plateau Mountain in Alberta.