The reason we get rockslides after heavy rain is because the rainwater enters cracks in the rock where as it freezes, it expands and opens the crack wider. As the thaw starts, the pieces of rock splinter and separate from the main rock.
Loose rock is continuously building up on a mountainside, but it is normally only the small pieces that slide down. This loose, broken rock is called ‘scree’. A rockslide will take place when a mass of this broken rock sliders down the side of a mountain mixed with a torrent of mud.
