The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline, at a depth of 1000 fathoms (1800 m) or more. The deepest part of the deep sea is Mariana Trench located in the western North Pacific. It is also the deepest point of the earth's crust. It has a maximum depth of about 10.9 km which is deeper than the height of Mount Everest. In 1960, Don Walsh and Jacques Piccard reached the bottom of Mariana Trench in the Trieste bathyscaphe. The pressure is about 11,318 metric tons-force per square meter (110.99 MPa or 16100 psi).