Near the island of Guam is the famous Mariana Trench where the Pacific Plate descends under the leading edge of the Eurasian Plate. Measured at 36,201 feet - over 6.8 miles (11 km) deep, this trench is the deepest known spot in any ocean. In 1960, two men in the bathyscaph "Trieste" reached bottom of the Mariana Trench. 