Freeze thaw, Snowdonia

The rocks on the rugged ridge (below) have been broken down into jagged fragments by the process of freeze-thaw weathering.

Water seeps into small cracks in the rock and freezes at night. When it freezes, it expands, and the ice gradually (over many cycles of freezing/thawing) prizes the rock apart.

Freeze-thaw weathering is common in regions where the temperature often drops below freezing at night. It does not happen much in warm climates, or in very cold places like Antarctica, where the temperature seldom rises above zero!