Conglomerate, Cornwall

Conglomerate is a rock made up of pebbles that have been transported and rounded by water, either in fast-flowing rivers or on beaches near the high tide mark. In the image below, you can see that the pebble deposit in the centre of the photo lies a couple of metres above the top of a modern pebble beach. It sits on solid rock well above the present-day high tide mark.

This deposit, known as a raised beach, was formed in a warm period about 120,000 years ago, before the last Ice Age that lasted until 10,000 years ago. The rubbly deposits above the raised beach conglomerate are called head and were formed as frozen ground melted in warmer periods during the Ice Age.