<P> Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced or sinks due to gravity into the mantle . Regions where this process occurs are known as subduction zones . Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries . </P> <P> Plates include both oceanic crust and continental crust . Stable subduction zones involve the oceanic lithosphere of one plate sliding beneath the continental or oceanic lithosphere of another plate due to the higher density of the oceanic lithosphere . That is, the subducted lithosphere is always oceanic while the overriding lithosphere may or may not be oceanic . Subduction zones are sites that usually have a high rate of volcanism and earthquakes . Furthermore, subduction zones develop belts of deformation and metamorphism in the subducting crust, whose exhumation is part of orogeny and also leads to mountain building in addition to collisional thickening . </P>

The process of forcing ocean crust into the mantle is called