மனிதன் பூமியை பிளந்து அடைந்த ஆழம் 12 கிலோமீட்டர்

மனிதன் பூமியை பிளந்து அடைந்த ஆழம் 12 கிலோமீட்டர்
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Kola Superdeep Borehole
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Kola Superdeep Borehole, commemorated on the 1987 USSR stamp
The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина) was the result of a scientific drilling project of the former USSR. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on May 24, 1970 on the Kola Peninsula, using an "Uralmash-4E" and later an "Uralmash-15000" drilling device. A number of boreholes were drilled by branching from a central hole. The deepest, SG-3, was completed in 1989, creating a hole 12,261 metres (about 40,226 feet or 7.62 miles) deep,[1] which is still the deepest hole ever drilled. The longest hole ever drilled is the 40,320 feet (about 12,290 meters or 7.64 miles) long Maersk Oil BD-04A well at Al-Shaheen field in Qatar[2].
Contents[hide]
1 Drilling
2 Research
3 Current status
4 Other projects
5 Well to Hell legend
6 References
7 External links
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[edit] Drilling
The project was first proposed in 1962 and was assigned to the Interdepartmental Scientific Council for the Study of the Earth's Interior and Superdeep Drilling (Russian: Межведомственный научный совет по проблемам изучения недр Земли и сверхглубокого бурения). The drill site was chosen in 1965 in north-west Soviet Union, 10 kilometres (6 mi) west of the town of Zapolyarny, at 69°23′N, 30°36′E
The initial target depth was set at 15,000 metres (49,210 ft). On June 6, 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma (9,583 metres (31,440 ft))[3] was broken. In 1983, the drill passed the 12,000 metres (39,370 ft) level, and drilling was stopped for about a year to celebrate the event.[4] This idle period may have contributed to a disappointing break-down on September 27, 1984: after drilling 12,066 metres (39,587 ft) down, 5,000 metres (16,400 ft) of boring pipes tore off and were left in the earth. It was decided to drill again from 7,000 metres (22,970 ft).[4] The hole reached 12,262 metres (40,230 ft) deep in 1989. In that year the hole depth was expected to reach 13,500 metres (44,290 ft) by the end of 1990 and 15,000 metres (49,210 ft) by 1993.[5] However, due to higher than expected temperatures at this depth and location, 180 °C (356 °F) instead of expected 100 °C (212 °F), drilling deeper was deemed unfeasible and the drilling was stopped in 1992.[4] With the expected further increase in temperature with increasing depth, drilling to 15,000 metres (49,210 ft) would have meant working at a projected 300 °C (570 °F), at which the drill bit would no longer work.

[edit] Research
The Kola borehole penetrated about a third through the Baltic continental crust, presumed to be around 35 kilometres (22 mi) thick, exposing rocks 2.7 billion years old at the bottom. The project has been a site of extensive geophysical studies. The stated areas of study were the deep structure of the Baltic Shield; seismic discontinuities and the thermal regime in the Earth's crust; the physical and chemical composition of the deep crust and the transition from upper to lower crust; lithospheric geophysics; and to create and develop technologies for deep geophysical study.
To scientists, one of the more fascinating findings to emerge from this well is that the change in seismic velocities was not found at a boundary marking Jeffreys' hypothetical transition from granite to basalt; it was at the bottom of a layer of metamorphic rock that extended from about 5 to 10 kilometers beneath the surface. The rock there had been thoroughly fractured and was saturated with water, which was surprising. This water, unlike surface water, must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock.
Another unexpected discovery was the large quantity of hydrogen gas, with the mud flowing out of the hole described as "boiling" with hydrogen.[6]

[edit] Current status
The site is currently controlled by the State Scientific Enterprise on Superdeep Drilling and Complex Investigations in the Earth's Interior (GNPP Nedra) as the Deep Geolaboratory. As of 2003, the deepest active bore is SG-5, at 8,578 metres (28,143 ft) deep and 214 mm (87⁄16 in) in diameter.