MARIANA TRENCH

submarine trench in the floor of the western North Pacific Ocean, situated east of the Mariana Islands. It is the deepest such trench known. An arcing depression, the trench stretches for more than 1,580 miles (2,550 km) with a mean width of 43 miles (69 km). There is a smaller steep-walled valley on the floor of the main trench. In 1899 Nero Deep (31,693 feet ) was discovered southeast of Guam. This sounding was not exceeded until a 32,197-foot (9,813-metre) hole was found in the vicinity 30 years later. In 1957, during the International Geophysical Year, the Soviet research ship Vityaz sounded a new world record depth of 36,056 feet (10,990 m). This was later increased to 36,201 feet (11,034 m). On Jan. 23, 1960, the French-built U.S. Navy-operated bathyscaphe Trieste, with the inventor's son, Jacques Piccard, aboard, made a record dive to 35,800 feet (10,911 m) in the trench.