SUBDUCTION ZONES

Subduction zones are where sediments, oceanic crust, and mantle lithosphere return to and reequilibrate with Earth's mantle. Subduction zones are interior expressions of Earth's 55,000 km of convergent plate margins and are the geodynamic system that builds island arcs. Excess density of the mantle lithosphere in subduction zones provides most of the power needed to move the plates while inducing convection in the overriding mantle wedge. Asthenospheric mantle sucked toward the trench by the sinking slab interacts with water and incompatible elements rising from the sinking plate, and this interaction causes the mantle to melt. These melts rise vertically through downwelling mantle to erupt at arc volcanoes.…