subduction zone

In plate tectonics, a region where two plates of the Earth's rigid lithosphere collide, and one plate descends below the other into the weaker asthenosphere. Subduction results in the formation of ocean trenches, most of which encircle the Pacific Ocean.

Ocean trenches are usually associated with volcanic island arcs and deep-focus earthquakes (more than 300 km/185 mi below the surface), both the result of disturbances caused by the plate subduction.