subductionzone

A subduction zone is a region where one tectonic plate sinks beneath another at a convergent plate boundary. It is a major feature of plate tectonics and a primary site of earthquakes, volcanism, and crustal recycling.

In subduction, a cold, dense oceanic plate descends into the mantle, creating a surface trench at the boundary with the overriding plate. As the slab sinks, water released from hydrous minerals lowers the mantle’s melting point, generating magmas that rise to form volcanoes on the overriding plate, and producing a volcanic arc. Sediments at the boundary are scraped off to form an accretionary wedge and a forearc basin. The descending slab can cause intense seismicity, including a Wadati-Benioff zone of earthquakes that extends to great depths along the slab.

Subduction zones can drive complex mantle flow and tectonic evolution. Slab rollback or changes in angle can create back-arc basins and influence arc activity. The two common configurations are oceanic-oceanic subduction, where one oceanic plate sinks beneath another, and oceanic-continental subduction, where a dense oceanic plate descends beneath a lighter continental plate. Continental-continental collision can interrupt or terminate subduction, often leading to crustal thickening and mountain building rather than a continuous subduction regime.

Subduction zones are central to crustal recycling and are major sources of megathrust earthquakes, volcanic eruptions, and associated hazards.