A detailed look at how caves, arches and stacks are formed at the coastline. Within a cliff face, there can be sections of weaker rock, which over time can erode to create caves. An arch starts off as two caves on a headland, but erosion takes it one step further and joins them together as an arch. Over hundreds of years, the arch becomes thinner and weaker until it comes crashing down, leaving a stack in the sea.

First broadcast:
22 November 2007

Children can investigate what coastal erosion is, and draw diagrams of the different forms of erosion caused by the wind and the sea. Then they can discuss ways to prevent erosion and shrinkage.