The first measurements (and discovery) of the Mariana Trench were made in 1875 from the British three-masted corvette Challenger (Challenge). Then, with the help of a deep-sea lot, the depth was set at 8367 meters (with repeated measurement - 8184 m) [9]. In 1951, an English expedition on the research ship Challenger recorded a maximum depth of 10,863 meters using an echo sounder. According to the results of measurements carried out in 1957 during the 25th voyage of the Soviet research vessel "Vityaz" by a group of scientists led by Alexei Dobrovolsky, the maximum depth of the trench is 11,022 m (updated data, the depth of 11,034 m was originally reported). Subsequently, it was the value of 11,022 meters that was indicated for the maximum depth of the Mariana Trench in Soviet educational and encyclopedic literature. The difficulty of measuring is that the speed of sound in water depends on its properties, which are different at different depths, so these properties must also be determined at several horizons with special instruments (such as a bathometer and a thermometer), and in the depth value shown by the echo sounder , amended. Studies in 1995 showed that it is about 10,920 m, and studies in 2009 - that 10971 m. Studies in 2011 give a value of 10994 meters with an accuracy of ±40 meters. Thus, the deepest point of the depression, called the Challenger Deep, is further from sea level than the top of Mount Everest is above it.
Amphipod Hirondellea gigas living at a depth of 10,900 m
Research conducted by the American Oceanographic Expedition from the University of New Hampshire (USA) discovered mountains on the surface of the bottom of the Mariana Trench. They took place from August to October 2010, when a bottom area of 400,000 square kilometers was studied in detail using a multibeam echo sounder. As a result, at least four oceanic mountain ranges 2.5 kilometers high were discovered, crossing the surface of the Mariana Trench at the point of contact of the Pacific and Philippine lithospheric plates. One of the researchers commented on this as follows: “In this place, the geological structure of the oceanic crust is very complex ... These ridges were formed about 180 million years ago in the process of constant movement of lithospheric plates. The marginal part of the Pacific Plate over the course of millions of years gradually “creeps” under the Philippine one, as an older and “heavy” one ... During this process, folding is formed ”
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