Volcanoes are found all over Earth. Many of them are on land. Many more volcanoes are found under Earth's oceans. If an underwater volcano keeps erupting, it can rise above the ocean's surface. An island is formed. The country of Iceland formed millions of years ago from underwater volcanic eruptions.
The story of a volcanic island starts inside the Earth. Earth has a solid inner core. It's made of solid metal. It is thought to be as hot as the surface of the sun! A liquid outer core surrounds the inner core. The outer core is made of metals, too. It is liquid because it is under less pressure than the inner core. Around the outer core is the Earth's mantle. It's made of hot rock called magma. It's mostly solid, but it can flow like hot plastic. We live on the crust. It is the thin, outside layer of the Earth. The crust is in pieces like a jigsaw puzzle. They are called tectonic plates. The plates fit together. Forces caused by Earth's heat sometimes push them tighter against each other. Sometimes forces pull them apart. Sometimes there are weak spots in the crust. When plates pull apart or there is a weak spot, the mantle's hot, flowing magma oozes out.