At the eastern edge of the Philippine Plate lies the volcanic island arc of the Northern Mariana Islands. To the east lies the Mariana Trench, where the Pacific Plate is subducting beneath the Philippine Plate. The Mariana Trench includes Challenger Deep—at 35,827 ft (10,920 m), this is the deepest known part of the ocean. It was named after a British survey ship that measured its depth in 1951. It was explored for the first time in 1960 by the deep-sea submersible Trieste, which found flatfish and shrimp living at the bottom of the trench.