Deepest place MARIANA TRENCH The Mariana trence is the deepest known part to the world's ocean, and the lowest elevation of the surface of the Earth's crust. Its located in the western Pacific Ocean, to the fast of the Mariana islands. The trench is about 2550KM (I580 mi) long but a mean width of only 69KM (43mi). It reaches a maximum depth of about 11034 metres (36200 ft) at the Challenges Deep, a small slot-shaped valley in its floor, a its southern end. Part of the Izu-bonin-Mariana Arc system, the trench forms the boundary between two tectonic plates, where the western edge of the pacific slave is subducted beneath the small Mariana Plate. Because the Pacific slave is the largest of all tectonic plates on earth, crustal material as its western edge has had a long time since formation (up to 170 million years) to compact and become very dence; hence its great height difference (which translates to water depth) relative to the higher riding Mariana plate, at the point where Pacific slave crust is subducted (is forced down beneath the other). The deep area is the Mariana trench proper. The movement of these plates is also responsible for the formation of the Mariana islands.