Mariana Trench, Submarine Trench In United States is the important seascape. The Mariana Trench is the deepest known ocean trench, with a maximum depth of about 11 kilometers, and the deepest location on the surface of the Earth. It is 2,542 kilometers long and 69 kilometers wide. It is located in the floor of the western North Pacific Ocean, to the east and south of the Mariana Islands, near Guam. The trench forms the boundary between two tectonic plates, where the Pacific Plate goes below the Philippine Plate. The bottom of the trench is farther below sea level than Mount Everest is above it, and the water pressure at this depth is over 8 tons per square inch, more than 1,000 times the standard atmospheric pressure at sea level.