What are volcanoes?

by Anthony

Volcanoes are leaks in the Earth's crust that allow hot, melted rock called magma or lava, to escape. Sometimes lava seeps out fairly quietly through a crack in the Earth's crust, destructive but slow enough for people to escape harm. Sometimes, though, magma piles up in a tube and escapes in a violent explosion. These more dangerous volcanoes are propelled by pent-up steam and carbon dioxide gas. Other poisonous gases may spew out along with ash and small rocks called "bombs."

Most of the Earth's volcanoes occur as a result of tectonic plates colliding or slipping against each other. These motions also cause earthquakes. Some volcanoes, as in Hawaii or Iceland, occur from cracks or hot spots in the Earth's crust.

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