MARIANA TRENCH

           The 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 1875, using a weighted rope, which recorded a depth of 4,475 fathoms. 

            In 1951, Challenger II surveyed the trench using echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. 

          In 1957, the Soviet vessel Vityaz reported a depth of 11,034 metres (36,201 ft) at a location dubbed the Mariana Hollow.

            In 1962, the surface ship M.V. Spencer F. Baird recorded a maximum depth of 10,915 metres (35,810 ft) using precision depth gauges.

             The Mariana Trench is a site chosen by researchers at Washington University and the Woods Hole Oceanographic Institution in 2012 for a seismic survey to investigate the subsurface water cycle. 

                Using both ocean-bottom seismometers and hydrophones, the scientists are able to map structures as deep as 97 kilometres (60 mi) beneath the surface