Volcanoes are formed when magma (liquid rock) trapped underneath the Earth’s crust rises to the surface and escapes through cracks. The space for the magma to leave is very small and ...

The graphic below shows how the movement of the Earth's tectonic plates causes volcanoes to be formed, and what triggers a volcanic eruption.

Shield volcanoes do not have such violent eruptions ... and magma here can gradually rise and form new crust, usually without any violent eruptions. Destructive plate boundaries are where tectonic ...