By Imogen Imbrignite Long ago, people used to think that volcanoes were caused by spirits or gods. The word volcano itself comes from Vulcan, who was the Roman god of fire. In the 1600's, they thought that volcanoes might be connected to a fire in the centre of the earth. Today, we know that volcanoes occur above thin parts of the earth's crust. The crust floats on top of molten rock called magma. Most of the time the crust is solid enough for us to stand on. But when an eruption happens, magma rises to the earth's surface and spills out onto the crust as lava. Superheated Science Question: What do you think causes a volcano to erupt? Normally we put volcanoes into three groups, active, dormant and extinct. An active volcano is one that has fairly regular eruptions. A dormant volcano is one that was active in the past, but is now quiet. If a volcano has not erupted in a very long time, and is not likely to do so again, then it is an extinct volcano.
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