The Earth Contents

3. Weathering

There are three main catalysts for physical weathering: heat, pressure and crystallization

Weathering can alter the shape of rocks.

During weathering the massive structure of rock is first broken down by physical processes to progressively smaller fragments. A variety of processes can be involved, but physical weathering is usually initiated by thermal expansion and contraction, expansion by pressure release and expansion by crystallisation. Rock faces may appear unyielding and impervious to change but the operation of physical processes over prolonged times are able to open up cracks which can be joined together to remove blocks of rock from the face. The scree slopes at the base of mountain rock faces are a clear expression of the efficiency of these processes.

What are the three main catalysts for physical weathering?