Oceanic Trench

An oceanic trench is a large linear oceanic depression with steep slopes on both sides. Most trenches are located in areas between a continental margin and island arcs or oceanic ridges. These trenches are parallel to the coastline of the mainland and are 2,000 m deeper than the surrounding seafloor. The depth usually exceeds 6,000 m, and the deepest can reach 11,000 m. They are several kilometres long and approximately 100 km wide. Most have an asymmetrical V-shaped cross-section, where the slope near the mainland is steeper than the slope near the ocean. The slopes always have terrace platforms. Deposits up to 1,500 m thick are located on the bottom. Together with island arcs, they form the modern active zone of the Earth’s crust; the island arc and oceanic trench system are always connected to active seismic and volcanic zones. Oceanic trenches are well developed in the Pacific margin; the Mariana Trench near the western margin is the deepest oceanic trench in the world, with a...