Process diagram: Formation of a volcanic island

The diagram shows how a volcanic island forms and later erodes, in a process that consists of eight stages.

Overall, the process is linear. The island is built up by volcanic activity beneath the sea, then it is colonised by plants, and it is finally worn away by the waves. The first five stages build the island, the next two allow life to become established, and the last wears the island away.

First, hot rock moves up through the sea floor as magma rises. Lava then breaks through under the ocean in an eruption, and it cools and hardens into solid rock. After repeated eruptions, a cone is built up, and eventually the peak rises above sea level so that an island appears. Each stage therefore depends on the one before it.

Once the island has appeared, life gradually becomes established. Weathering creates soil, and seeds are brought to the island by birds and wind, so that plants arrive.

In the final stage, the island is slowly worn away by the waves in a process of erosion.