subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to a volcanic island arc, and about 200 km (120 mi) from a volcanic arc. hence the age of ocean floor is usually greatest in subduction zones
This occurs in a subduction zone.
Trench
C. subduction zone
The deepest parts of the ocean floor are caused by plate tectonic subduction and occur where the sea floor sinks back into the mantle in a subduction zone. These areas are called deep sea trenches and the Challenger Deep in the Mariana Trench in the Pacific is the deepest known point in Earth's oceans.
A subduction zone occurs at convergent plate margins where an oceanic plate is going underneath a continental plate or a less dense oceanic plate. A mid-ocean ridge is a divergent plate boundary on the ocean floor with a mountain range and a rift running through the center of it. Sea floor spreading also occurs at mid ocean ridges.
The magma spills over the ridge and pushes the old sea floor away toward a subduction zone where the old sea floor melts.
The ocean floor is the most anaerobic zone in the ocean.
This is called the subduction zone.
Subduction Zone
A subduction zone forms when one oceanic plate is forced beneath another plate. This process can lead to the formation of volcanic arcs, deep ocean trenches, and seismic activity.
A destructive plate boundary (WITH a subduction zone!)
The Mariana Trench in the western Pacific Ocean is the deepest place on Earth, reaching a depth of about 36,070 feet. The trench is formed by the subduction of the Pacific Plate beneath the Mariana Plate. This process creates a deep trench in the ocean floor.