Answer:
The subducting plate (oceanic) dives downward toward the mantle. Because of the geothermal gradient, temperature with depth increases; this, along with the introduction of large amounts of water which is present in the oceanic crust, will result in partial melting of the subducting lithosphere . The melting occurs in the asthenosphere, which is the ductile rock of the upper mantle. Because the magma is less dense than the surrounding rock, it will rise, and may result in the formation of plutonic rock deep underground, or in the eruption of lava onto the surface.