Subduction zone

A subduction zone is formed where two tectonic plates come together and one plate overrides the other. The plate with lower density, usually comprised of continental crust, stays on top while the denser plate, usually made of oceanic crust, is pushed and pulled beneath, into Earth’s mantle. As the subducting oceanic plate descends into the Earth, volatiles such as water are liberated, promoting melting above, and eventually volcanoes at the surface. The Pacific Rim of Fire is a series of subduction zones, and the volcanoes along the ring are a result of this subduction. Mount Shasta and Lassen Peak in California are both subduction-related volcanoes.