The Mariana Trench is located in the Pacific Ocean,  just east of the 14 Mariana Islands (11"21' North latitude and 142" 12' East longitude ) near Japan.   As you probably already know, it is the deepest part of the earth's oceans, and the deepest location of the earth itself.  It was created by ocean-to-ocean subduction, a phenomena in which a plate topped by oceanic crust is subducted beneath another plate topped by oceanic crust.

The bottom there is 10,924 meters (35,840 feet) below sea level. If Mount Everest, the highest mountain on Earth, were placed at this location it would be covered by over one mile of water. The Challenger Deep is named after the British survey ship Challenger II, which discovered this deepest location in 1951. 

According to Jacques Piccard (born July 28, 1922) is a Swiss explorer and engineer, known for having developed underwater vehicles for studying ocean currents. He is the only person (as of 2008), along with Lt. Don Walsh, to have reached the deepest point on the earth's surface, the Challenger Deep, in the Mariana Trench.

On January 23, 1960, Jacques Piccard and Don Walsh reached the ocean floor in the Challenger Deep with his bathyscaphe Trieste. The depth of the descent was measured at 10,916 meters (35,813 feet), later more accurate measurements in 1995 have found the Challenger Deep to be less deep at 10,911 m (35,797 ft). The descent took almost five hours and the two men spent barely twenty minutes on the ocean floor before undertaking the 3 hour 15 minute ascent.

The maximum surveyed depth of the Challenger Deep is 10,923 meters (35,838 feet) or 6.7875 miles. (National Geographic puts the depth at 10,920.07 meters (35,827 feet) below sea level.) The pressure at this depth is approximately 1,095 times that at the surface, or 110 MPa.

The HMS Challenger Expedition (December 1872 – May 1876) first sounded the depths now known as the Challenger Deep. This first sounding was made on 23 March, 1875 at station 225. The reported depth was 4,475 fathoms (8,184 m, 26,850 ft), based on two separate soundings.

The questions is why is the ocean so deep here?, the answer is because The Mariana Trench is located at a convergent plate boundary. Here two converging lithospheric plates collide with one another. One of the plates descends into the mantle. At the line of contact between the two plates the downward flexure forms a trough known as an ocean trench.

According to BBC News, The climate secrets of the deepest part of the ocean, the Marianas Trench in the western Pacific Ocean, have been probed by scientists. The international team used a submersible, designed to withstand immense pressures, to study the bottom of the 10.9km-deep underwater canyon.


Their early results reveal that ocean trenches are acting as carbon sinks. This suggests that they play a larger role in regulating the Earth's chemistry and climate than was thought. Although two explorers, Jacques Piccard and Don Walsh, reached the deepest part of the Marianas Trench - a point called the Challenger Deep - in 1960, no humans have been back since. And the handful of scientific missions, including this recent visit to this deepest spot, have been carried out using unmanned underwater vehicles.

Lead researcher Professor Ronnie Glud, from the University of Southern Denmark and the Scottish Association for Marine Science (Sams), said that working at more than 1,000 atmospheres of pressure was challenging, but advances in technology had made it possible.

He told BBC News: "This is the first time we have been able to set down sophisticated instruments at these depths to measure how much carbon is buried there."