What is a volcano?

A volcano is a mountain that opens downward to a reservoir of molten rock below the surface of the earth

When the volcano erupts, magma is drawn from the shallow storage area, and the ground above it subsides to fill the space

If a large amount of magma is withdrawn rapidly from the storage area, the ground will collapse, and this is the process in which pit craters are formed.

Theories about volcanoes!

Volcanoes 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

What causes volcanoes?

On land, volcanoes form when one tectonic plate moves under another

Usually a thin, heavy oceanic plate subducts, or moves under, a thicker continental plate