Final answer:
Subduction is a geological process at convergent plate boundaries where oceanic lithosphere descends into the mantle beneath another plate, often marked by features like ocean trenches.
Step-by-step explanation:
The process described in the question is known as subduction, a geological phenomenon that occurs at convergent plate boundaries. Subduction entails the sideways and downward movement of the oceanic lithosphere into the mantle beneath another tectonic plate. This process is a critical component of the plate tectonics theory that explains the movement of the Earth's crust. The descending plate is forced into higher pressure and temperature conditions within the mantle, leading to its eventual melting and recycling within a downward-flowing convection current.
Subduction zones play a crucial role in shaping the Earth's surface, often being marked by geologic features such as ocean trenches. An example of this is the deep Japan trench along the coast of Asia. The subducted material balances the new crust that is formed at rift zones, following the principle that the amount of crust destroyed at subduction zones approximately equals the amount formed at rift zones.