has anyone been to the bottom of the mariana trench
Mariana Trench Four descents have been achieved. The first was the manned descent by Swiss-designed, Italian-built, United States Navy-owned bathyscaphe Trieste which reached the bottom at 1:06 pm on 23 January 1960, with Don Walsh and Jacques Piccard on board.[13][22] Iron shot was used for ballast, with gasoline for buoyancy.[13] The onboard systems indicated a depth of 11,521 m (37,799 ft), but this was later revised to 10,916 m (35,814 ft).[23] The depth was estimated from a conversion of pressure measured and calculations based on the water density from sea surface to seabed.[22]
Mariana Trench 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.