Oceanic trench the level of the surrounding oceanic floor. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km/yr. There are approximately of convergent plate margins, mostly around the Pacific Ocean—the reason for the reference “Pacific-type” margin—but they are also in the eastern Indian Ocean, with relatively short convergent margin segments in the Atlantic Ocean and in the Mediterranean Sea. Globally, there are over 50 major ocean trenches covering an area of 1.9 million km or about 0.5%
Tongue of the Ocean Tongue of the Ocean The Tongue of the Ocean (TOTO) is the name of a deep oceanic trench in the Bahamas separating the islands of Andros and New Providence. The TOTO is a U-shaped, relatively flat-bottomed trench approximately 20 miles (32 km) wide by 150 miles (240 km) long. Its depth varies gradually from 3,600 feet (1,100 m) in the south to 6,600 feet (2,000 m) in the north. Its only exposure to the open ocean is at the northern end. Except for the northern ocean opening, the TOTO is surrounded by numerous islands, reefs, and shoals which make a