What Is An Oceanic Trench?
An oceanic trench is a long and narrow depression in the ocean floor. These trenches are considered the deepest part of the ocean floor, occurring at the boundary between convergent plates and lithospheric plates. These plates slowly move toward each other at distances that range from a few millimeters per year to more than 10 centimeters. The trench is created when one of the plates slides below the lithospheric slab. Generally, oceanic trenches reach between 1.9 and 2.5 miles below the nearby ocean floor. This article takes a look at some of the deepest oceanic trenches in the world.
The Four Deepest Oceanic Trenches In The World
The Challenger Deep is the deepest spot in the ocean floor. It reaches between 35,755 and 36,197 feet below the nearby surface of the seabed, depending on how it is measured (either by sonar bathymetry or submersibles. It is located near the Mariana Islands of the Pacific Ocean within the Mariana Trench, which is also a significantly deep location in the ocean floor. The Challenger Deep has been descended on 4 separate occasions. The first descent took place in 1960 by a manned bathyscaphe vehicle, the Trieste. The second descent was in 1995, this time by an unmanned remotely operated underwater vehicle (ROV), named Kaiko. In 2009, the ROV Nereus made the descent. The most recent descent was made in 2012 by a manned deep submergence vehicle, the Deepsea Challenger.
The Tonga Trench is the second deepest site in the ocean floor at 35,702 feet below the level of the sea floor. It is located in the South Pacific Ocean, on the northern side of the Kermadec-Tonga Subduction Zone. This area is considered an active submergence zone, which means the Pacific plate is continuing to slide beneath both the Tonga and Indo-Australian plates. This makes the Tonga Trench an important site for further scientific research into the formation of the ocean floor and oceanic trenches. The rate at which these plates are converging is the fastest-recorded in the world, reaching between 6 and 9 inches per year. Interestingly, this trench is also the site of the radioisotope thermoelectric generator from the Apollo 13 mission.
The Galathea Depth is the third deepest site in the world. It is located in the western Pacific Ocean, within the Philippine Trench. It reaches 34,580 feet below the level of the ocean floor. One of the first explorations of this site took place in 1950 by a Danish exploration team, whose original objective was to collect fauna from the bottom of the ocean.
The fourth deepest oceanic trench in the world is the Kuril-Kamchatka Trench, located in the northwest region of the Pacific Ocean. This trench reaches 34,449 at its deepest. It runs from a junction of the Ulakhan and Aleutian Trenches and crosses the Japan Trench to the southwest. The formation of this trench dates back to the Cretaceous era and the subduction that led to the creation of the Kuril Island Arc and the Kamchatka Volcanic Arc. Today, the Pacific Plate continues to slide under the Othotsk Plate, producing extreme volcanism and seismic activity in the area. This movement is taking place at a rate of between 75 and 83 millimeters per year.
Additional oceanic trenches can be seen in the chart published below.