What is the name of the boundary where one tectonic plate descends beneath another?

A subduction zone is the boundary where one tectonic plate descends beneath another. Usually, the denser oceanic lithosphere sinks into the mantle beneath oceanic or continental lithosphere, recycling crust into Earth’s interior.

Subduction zones produce deep ocean trenches, powerful earthquakes, volcanic arcs, and mountain belts. Water and other volatiles released from the descending slab help generate magma in the mantle wedge above it. That magma can rise to form chains such as the Andes or island arcs such as Japan and the Aleutians.

Subduction is not the same as any convergent boundary. Continental collision can occur when two buoyant continents meet, but neither continent easily sinks deep into the mantle. Transform boundaries mainly involve horizontal sliding, and divergent boundaries are where plates move apart. The Pacific Ocean is bordered by many subduction zones, contributing to the “Ring of Fire.”