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When you are done with this section, take the Volcanoes Quiz.

A volcano is a mountain or hill formed around a crack in the earth's crust. This crack allows molten rock and other hot materials to be thrown out from the earth.

The rock inside the earth's mantle is very hot, but solid because of the great pressure on it. When the pressure upon some of this solid rock is reduced or there is an escape route through a crack, the rock becomes a liquid called magma.

The magma is forced up and then spurts out of the crack. Gases, often poisonous is also forced out.When the magma come to the surface, it is called lava.

Volcanoes erupt differently. Some erupt quietly and the lava flows down the side of the volcano and some are more violent.

The opening in the top of the volcano is called a crater. Some craters are filled with water and become lakes such as the Crater Lake in Oregon.

Most volcanoes occur in the same area as two earthquake belts. One circles the Pacific Ocean and the other is around the Mediterranean and Asia Minor.

Volcanoes are classified as:

 

To learn more about volcanoes, go to these sites: