Nansei Trench

(also Ryukyu Trench), a submarine depression in the western Pacific, extending along the Nansei (Ryukyu) Islands for almost 1,500 km. The trench has a transverse profile. In places the bottom is flat, up to 20 km wide, and divided by rises into individual depressions. The maximum depth is 7,507 m; it was measured in 1925 by the Japanese hydrographic ship Manshu.