Mariana Trench

Mariana Trench:

The Mariana Trench or Marianas Trench is the deepest known part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres (1,580 mi) long but has an average width of only 69 kilometres (43 mi). It reaches a maximum-known depth of 10,994 m (± 40 m) or 6.831 mi (36,070 ± 131 ft) at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end, although some unrepeated measurements place the deepest portion at 11.03 kilometres (6.85 mi).

At the bottom of the trench the water column above exerts a pressure of 1,086 bars (15,750 psi), over 1000 times the standard atmospheric pressure at sea level. At this pressure, the density of water is increased by 4.96%, making 95 litres of water under the pressure of the Challenger Deep contain the same mass as 100 litres at the surface. The temperature at the bottom is 1 to 4 °C.

The trench is not the part of the seafloor closest to the center of the Earth. This is because the Earth is not a perfect sphere; its radius is about 25 kilometres (16 mi) less at the poles than at the equator.[5] As a result, parts of the Arctic Ocean seabed are at least 13 kilometres (8.1 mi) closer to the Earth's center than the Challenger Deep seafloor.

Xenophyophores have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of 10.6 km (6.6 mi) below the sea surface. On 17 March 2013, researchers reported data that suggested microbial life forms thrive within the trench.




The picture shows how deep the trench is. Click on it to look at it closer.


Life in Mariana Trench:

The expedition conducted in 1960 observed (with great surprise because of the high pressure) at the bottom large living creatures such as a flatfish about 30 cm (1 ft) long, and a shrimp.According to Piccard, "The bottom appeared light and clear, a waste of firm diatomaceous ooze".Many marine biologists are now skeptical of the supposed sighting of the flatfish, and it is suggested that the creature may instead have been a sea cucumber.

During the second expedition, the unmanned vehicle Kaikō collected mud samples from the seabed. Tiny organisms were found to be living in those samples.

In July 2011, a research expedition deployed untethered landers, called dropcams, equipped with digital video and lights to explore this region of the deep sea. Amongst many other living organisms, some gigantic single-celled amoebas with a size of more than 4 in (10 cm), belonging to the class of xenophyophores were observed. Xenophyophores are noteworthy for their size, their extreme abundance on the seafloor and their role as hosts for a variety of organisms.


In December 2014, a new species of snailfish was discovered at a depth of 8,145 m (26,722 ft), breaking the previous record for the deepest living fish seen on video. Several other new species were also filmed, including huge crustaceans known as supergiants.


Geography:

The Mariana Trench is part of the Izu-Bonin-Mariana subduction system that forms the boundary between two tectonic plates. In this system, the western edge of one plate, the Pacific Plate, is subducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west. Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is therefore cooler and more dense; hence its great height difference relative to the higher-riding (and younger) Mariana Plate. The deepest area at the plate boundary is the Mariana Trench proper.


The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands. These volcanic islands are caused by flux melting of the upper mantle due to release of water that is trapped in minerals of the subducted portion of the Pacific Plate.