Landform 2 - submarine volcanoes

You've almost certainly heard of volcanoes, but did you know that there are more than a million volcanoes under the sea as well? In fact, that's how many islands form. When hot magma in the Earth's crust breaks through the ocean floor due to intense pressure, it is called a submarine volcanic eruption. Over hundreds of years, the volcano increases in size as every time the volcano erupts, magma solidifies on the top. When the volcano gets so big that it breaks the surface of the ocean, a volcanic island is formed. This occurred in the 1960s off the coast of Iceland when the island Surtsey literally erupted out of the sea. The Galapagos Islands and the Hawaiian Islands, among others, were also formed in this way. Below is a picture of Surtsey during its eruption.

When submarine volcanoes are still submarine, however, they are often the sites of hydrothermal vents, or black smokers. Water, hydrogen sulphide, and other minerals pour from these springs at temperatures of about 350°C. These hot waters host an ecosystem complete with giant clams, mussels, tube worms, and other creatures, that use sulphur, not sunlight, to live.

Watch a short video clip about hydrothermal vents here.

Watch an erupting submarine volcano here.