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%
Hjort Trench below sea level. To the east, the Hjort ridge follows the general curve of the trench, separating the trench from the Hjort Plateau. The Hjort trench lies in an area of transpression where the plate boundary transitions from a transform boundary to a convergent one. As such, this region provides an example of how a transform boundary with a vertical or near-vertical transform fault becomes an area of under-thrusting. Hjort Trench The Hjort Trench is a linear topographic depression south of Macquarie Island in the southwest Pacific Ocean. Geologically, the depression is considered to be the seafloor expression of an