Why do volcanoes erupt?

At about two miles below the surface to the Earth the temperature is high enough to boil water. If it were possible to dig down 30 miles, the temperature would be about 2,200 degrees fahrenheit. This is hot enough even to melt rocks. At the centre of the Earth scientists believe that the temperature could be as high as 10,000 degrees fahrenheit. When rock melts, it expands and needs more space. When the pressure is greater than the roof of rock above it, it bursts out causing an eruption. When the volcano erupts it throws out hot, gaseous liquid called lava or solid particles that look like cinders and ash. The material piles up around the opening and a cone-shaped mound is formed.

Fact file

A dormant volcano is one that is actually 'sleeping'. A dormant volcano might erupt in the future. An extinct volcano, on the other hand, will not become active again.

resources: Tell me why (Chancellor Press)
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