Mariana Trough - Location and Bathymetry

Location and Bathymetry

The Mariana Trough stretches 1300 km from north to south, about the distance from Los Angeles CA to Portland OR, Tokyo, Japan to Seoul, Korea, or London, England to Rome, Italy. The Mariana Trough has roughly the dimensions and areal extent of Japan or California. The Trough is crudely crescent-shaped, opening on the south; it is bounded to the east by the active Mariana arc, to the west by the remnant arc of the West Mariana Ridge (Karig 1972), and to the south by the Challenger Deep, part of the Mariana Trench. It narrows northward until the Mariana arc and West Mariana Ridge meet at about 24°N. It is widest in the middle, at 18°N, where it is about 240 km wide, and narrows to about half this at its southern, open end. Depths in the basin are distributed asymmetrically, being greater adjacent to the West Mariana Ridge than next to the active arc, due to a westward-thinning wedge of volcaniclastic sediments derived from the active arc, and also less thermal buoyancy of the mantle. Where not covered by sediments, the seafloor is deeper and bathymetry more rugged than normal. The most recent, "zero-age" seafloor of the Philippine Sea, including the Mariana Trough, lies at a mean depth of 3200 m compared to normal zero-age seafloor depths of 2500 m (Park, Tamaki & Kobayashi 1990).