TONGA TRENCH

submarine trench in the floor of the South Pacific Ocean, about 850 miles (1,375 km) in length, forming the eastern boundary of the Tonga Ridge; the two together constitute the northern half of the Tonga-Kermadec Arc, a structural feature of the Pacific floor completed to the south by the Kermadec Trench and Ridge. The Tonga Trench has an average depth of 20,000 feet (6,000 m) and a width of about 50 miles (80 km); it reaches a maximum depth of 35,702 feet (10,882 m).