The Mariana Trench or Marianas Trench is located in the western Pacific Ocean approximately 200 kilometres (124 mi) east of the Mariana Islands, and has the deepest natural point in the world. It is a crescent-shaped trough in the Earth's crust averaging about 2,550 km (1,580 mi) long and 69 km (43 mi) wide. The maximum known depth is 10,994 metres (36,070 ft) (± 40 metres [130 ft]) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep.

The trench is not the part of the seafloor closest to the centre of the Earth. This is because the Earth is not a perfect sphere; its radius is about 25 kilometres (16 mi) smaller at the poles than at the equator. As a result, parts of the Arctic Ocean seabed are at least 13 kilometres (8.1 mi) closer to the Earth's centre than the Challenger Deep seafloor.

In 2009, the Marianas Trench was established as a United States National Monument.

More Info: en.wikipedia.org