subduction

The process by which one tectonic plate descends beneath another and sinks into the earth's mantle — the recycling mechanism of the planet's surface. At subduction zones, oceanic crust dives beneath continental or other oceanic crust at rates of a few inches per year, generating the planet's most powerful earthquakes, its deepest ocean trenches, and its most explosive volcanic chains. The Pacific Ring of Fire is a ring of subduction zones. The Cascadia subduction zone runs from northern California to British Columbia, where it is overdue for a magnitude-9 earthquake that will reshape the Pacific Northwest.