Explosion after explosion of hot rock and ash spurted from the ocean.
A thick cloud of steam rose high into the air.
Slowly, for many days, a long mound of dark lava rose up out of the water.
An island had been born!
An island, of course, is a piece of land with water all around it.
But the land doesn't float on the water.
What you see is the top of land that sticks up from the bottom of the sea.
Most islands far out in the ocean are actually the tops of underwater volcanoes!
Volcanic islands are made when underwater volcanoes erupt, pouring out red-hot, melted rock. The rock quickly cools and hardens in the water, building up into a big, cone-shaped mountain.
The island is the top of the cone.
All islands aren't volcanoes.
Most islands in lakes and rivers are high pieces of land that stick out of the water. Some islands are formed when the sea separates them from the mainland.
Great Britain was not always an island. At one time, a low plain joined it to Europe. Thousands of years ago, the sea covered this plain.
Island of Surtsey, Iceland
Most islands in the ocean are the tops of underwater volcanoes. The picture shows such an island being born. Smoke from the underwater volcano is pouring up. Below, the top of the volcano has risen from the water.