A volcano is an opening, or rupture, in a planet’s surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface.
They are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. Volcanoes can also form where there is stretching and thinning of the Earth’s crust in the interiors of plates.
There is no consensus among volcanologists on how to define an “active” volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations.
Scientists usually consider a volcano to be erupting or likely to erupt…
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