When one oceanic plate subducts under the other, a subduction zone will form. The oceanic plate that subducts will sink back into the mantle, forming a volcanic arc.
Explanation:
Subduction is a process that takes place when two tectonic plates collide, and one plate moves under another and is forced to sink into the mantle.
When two oceanic plates collide one oceanic plate is eventually subducted under the other. Where one plate slides under the other is referred to as the subduction zone. As the subducting plate descends into the mantle where it is being gradually heated a deep ocean trench is formed, and magma formed above the subducting plate slowly rises into the overriding crust and finally to the surface forming a volcanic arc.
