subduction zone

The boundary where one tectonic plate descends beneath another. Subduction zones produce the three most destructive geological phenomena on earth simultaneously: megathrust earthquakes (the largest quakes possible, including the 2004 Indian Ocean and 2011 Tōhoku events), explosive volcanism (the Cascades, the Andes, Japan's volcanic arc), and tsunamis triggered by sudden seafloor displacement. They are the most consequential boundaries on the planet's surface.