Physical Weathering

Question 1

Freeze-thaw

Answer 1

Water enters cracks/joints and expands by nearly 10 per cent when it freezes. In confined spaces, this exerts pressure on the rock causing it to split or pieces to break off, even in very resistant rocks. The more frequent and regular the fluctuations of temperature around zero, the more effective this process will be.

Question 2

Frost shattering

Answer 2

At extremely low temperatures, water trapped in rock pores freezes and expands. This creates stress which disintegrates rock to small particles.

Question 3

Pressure release

Answer 3

When the weight of overlying ice in a glacier is lost due to melting, the underlying rock expands and fractures parallel to the surface. This is significant in the exposure of sub-surface rocks such as granite and is also known as dilatation. The parallel fractures are sometimes called pseudo-bedding planes.