Hadal Trench Environment and Current Research
The hadal is the deepest part of the ocean, with depths ranging from 6,000 to 11,000 meters. There are 46 hadal zones on our planet, including 33 trenches and 13 troughs, with the Mariana trench being the world's deepest. Troughs are groups of deep-sea basins that do not originate at plate intersections, whereas trenches are V-shaped cross-section areas that are typically long and narrow, and geographically isolated from one another. Of the 33 trenches, 26 are located in the Pacific Ocean, 3 in the Atlantic Ocean, 2 in the Indian Ocean, and 2 in the Southern Ocean. The hadal zone covers less than 1% of the entire ocean surface area yet accounts for 45 percent of entire ocean depth. Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers (30 to 60 mi) wide and 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about 50,000 kilometers (31,000 mi) of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m (36,201 ft) below sea level.
Oceanic trenches, in particular, are a hallmark of convergent plate borders, which occur when two or more tectonic plates collide. Dense lithosphere dissipates or slips beneath less dense lithosphere at numerous convergent plate borders, generating trenches in the process known as subduction. Deep-sea trenches have a V-shaped cross section, with the landward side being steeper. A typical trench's temperature ranges between 1 and 4 degrees Celsius at the bottom. In addition to low temperatures, hydrostatic pressure rises by one atmosphere (atm) for every 10 meters of depth, bringing the pressure in the hadal zone to around 600 to 1,100 atm. The trench is one of the most peculiar environments on Earth due to its extreme pressure, lack of sunlight, and frigid temperatures.
