MARIANA TRENCH
T he Mariana Trench or Mariana Trench is located in the western Pacific Ocean about 200 kilometres (124 mi) east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent - shaped and measures about 2,550 km (1,580 mi) in length and 69 km (43 mi) in width. At the bottom of the trench, the water column above exerts a pressure of 1,086 bars (15,750 psi), more than 1,071 times the standard atmospheric pressure at sea level. At this pressure, the density of water is increased by 4.96%. The temperature at the bottom is 1 to 4 °C (34 to 39 °F). In 2009, the Marianas Trench was established as a US National Monument.Monothalamea have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of 10.6 kilometres (6.6 mi) below the sea surface. Data has also suggested that microbial life forms thrive within the trench. HISTORY :- The trench was first sounded during the Challenger expedition in