Mechanical Weathering – Weathering process that causes physical disintegration or break-up of exposed rock without any change in the chemical composition of the rock, for instance freeze thaw

To remember the meaning of the term Mechanical Weathering, use the following mnemonic:

The mechanics all worked on a machine which, when there was bad weather (mechanical weathering), would break up the rock.

There are two main types of mechanical weathering: freeze-thaw and exfoliation.

To learn about freeze-thaw, click the link. 

Exfoliation occurs when daytime and night-time temperatures are vastly different on dry rock. During the day, the sun heats up the surface of the rock and at night the outer layers cool down. The continual expansion and contraction gradually disintegrates the top layers.