Subduction zone

A convergent tectonic boundary where one plate, usually oceanic, descends beneath another into the mantle. It generates deep earthquakes, volcanic arcs, and recycles oceanic lithosphere.

Wadati–Benioff zone: An inclined zone of earthquake foci that traces a descending tectonic plate into the mantle. Its dipping earthquake pattern maps the slab as it sinks beneath the overriding plate.
Megathrust earthquake: A very large earthquake caused by sudden slip along a locked boundary between converging tectonic plates. The shallow plate interface can rupture over vast areas, producing the largest earthquakes.
Cascadia subduction zone: A subduction zone where the Juan de Fuca plate descends beneath the North American plate. Its offshore interface can produce great earthquakes and threatens the Pacific Northwest.
Plate tectonics: The theory that Earth's outer shell consists of moving plates whose interactions shape the surface. Subduction is one of the central processes by which tectonic plates interact.
Transform boundary: A plate boundary where two plates slide horizontally past one another. Unlike subduction, transform motion neither consumes a plate nor requires descent into the mantle.
Slab pull: The force exerted as dense oceanic lithosphere sinks into the mantle and pulls the rest of its plate. The sinking slab helps drive plate motion toward the trench.
Tsunami: A series of long-wavelength ocean waves generated by sudden displacement of seawater. Vertical seafloor motion during major subduction earthquakes can launch destructive tsunamis.
Japan Trench: A deep ocean trench east of Japan where the Pacific plate subducts beneath the islands. The 2011 Tōhoku earthquake ruptured the plate boundary near this trench.
Oceanic lithosphere: The rigid outer layer of Earth beneath ocean basins, comprising oceanic crust and uppermost mantle. Its density and age help determine whether it sinks beneath another plate.
Divergent boundary: A plate boundary where two plates move apart and new lithosphere forms between them. It creates oceanic lithosphere, whereas subduction removes it.

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