What is a volcano?

A volcano is a vent or 'chimney' that connects molten rock (magma) to the Earth's surface. It includes the surrounding cone of built-up material. Magma erupting from a volcano is called lava. Gases and pieces of rock erupt from volcanoes too.

A volcano is active if it erupts lava, releases gas or shows seismic activity. It is dormant if it hasn't erupted for a long time but could again one day. An extinct volcano will never erupt again.

The explosiveness of a volcanic eruption depends on how easily magma can flow and the amount of gas trapped in it. Large amounts of water and carbon dioxide are dissolved in magma. They behave like gas in fizzy drinks. After opening the bottle the gas expands, forming bubbles that escape. This also happens when magma rises quickly through the crust - gas bubbles form and expand up to 1000 times their original size.

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volcano?