Mariana Trench
Micronesia, Pacific Ocean
Earth's Natural Wonders in Australia & Oceania
Length of the Marianna Trench: 1,580 miles
Width of Trench: 43 miles
Depth of Challenger Deep:36, 197 feet deep	Mariana trench- NOAA/National Geographic[1]

 

The Swiss-designed, Italian-built, United States Navy bathyscaphe Trieste reached the bottom at 1:06 p.m. on January 23, 1960, with U.S. Navy Lieutenant Don Walsh and Jacques Piccard on board. Iron shot was used for ballast, with gasoline for buoyancy. The onboard systems indicated a depth of 11,521 meters (37,799 ft), but this was later revised to 10,924 meters(35,813 ft) . At the bottom, Walsh and Piccard were surprised to discover soles or flounder about 30 cm (1 ft) long, as well as shrimp. According to Piccard, "The bottom appeared light and clear, a waste of firm diatomaceous ooze".[2]

The bathyscaphe Trieste as it appeared just before the record dive to the floor of the Marianas Trench. Image: Courtesy of the U.S. Navy

The Woods Hole Oceanographic Institution sent its Nereus hybrid remotely operated vehicle (HROV) to explore the trench on May 31, 2009.[2]

 

The Mariana Trench (or Marianas Trench) is the deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 1580 miles (2550 km) long but has a mean width of only 43 miles (69 km). It reaches a maximum depth of about 10,924 meters at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end. (35,840 feet; 6.78 miles).

Part of the Izu-Bonin-Mariana Arc system, the trench forms the boundary between two tectonic plates, where the western edge of the Pacific Plate is subducted beneath the small Mariana Plate. Because the Pacific plate is the largest of all the tectonic plates on Earth, crustal material at its western edge has had a long time since formation (up to 170 million years) to compact and become very dense; hence its great height-difference (which translates to water depth) relative to the higher-riding Mariana Plate, at the point where the Pacific Plate crust is subducted (is forced down beneath the other). This deep area, is the Mariana trench proper. The movement of these plates is also responsible for the formation of the Mariana Islands.

At the bottom of the trench, where the plates meet, the water column above exerts a pressure of 108.6 MPa, over one thousand times the standard atmospheric pressure at sea level. Some creatures of the type normally encountered that could live at these depths are few, but some fish species, like the angler fish or other deep-sea fishes, have been spotted in these waters.[citation needed] If Mount Everest, the tallest point on Earth at 8,848 meters (29,029 feet), were set in the Mariana Trench, there would be 2,076 meters (6,811 feet) of water left above it.[2]

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The trench was first sounded during the Challenger expedition (December 1872 – May 1876), which recorded a depth of 9,636 m (31,614 feet).

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. During this survey, the deepest part of the trench was recorded when the Challenger II measured a depth of 5,960 fathoms (10,900 metres, 35,760 ft) at 11°19'N 142°15'E? / ?11.317°N 142.25°E? / 11.317; 142.25,[3] known as the Challenger Deep.[2]

In 1957, the Soviet vessel Vityaz reported a depth of 11,034 meters (36,200 ft), dubbed the Mariana Hollow. (Although this claim was made by the Soviets in 1957, the finding has not been repeated by subsequent mapping expeditions using more accurate and modern equipment.)[citation needed]

In 1962, the surface ship M.V. Spencer F. Baird recorded a maximum depth of 10,915 meters (35,840 ft), using precision depth gauges.

In 1984, the Japanese sent the Takuyo , a highly specialized survey vessel, to the Mariana Trench and collected data using a narrow, multi-beam echo sounder; they reported a maximum depth of 10,924 meters, also reported as 10,920 meters ± 10 meters.

The most accurate measurement on record was taken by a Japanese probe, Kaiko , which descended unmanned to the bottom of the trench on March 24, 1995 and recorded a depth of 10,911 meters (35,798 ft).[2]