Volcanoes are thought to form in three settings: where tectonic plates are diverging (for instance at mid-ocean ridges); where tectonic plates are converging (in island arcs, for example); and in "hotpots" (a generic term for volcanic activity that cannot be attributed to plate tectonic movements. Hotspots are generally thought to be formed by hot, buoyant plumes rising rapidly from the boundary between Earth's core and the mantle.
