The Kola Superdeep Borehole in Russia is the deepest hole ever drilled, reaching 7.6 miles deep in 1981. It only penetrated a third of the Baltic continental crust and discovered 2.7 billion-year-old rock. Rumors of reaching hell were false, but interesting discoveries were made, including pockets of water and excess hydrogen.
The deepest hole ever drilled is the Kola Superdeep Borehole, on the Kola Peninsula in the northwestern corner of Russia, near Finland. It was drilled for scientific research by the USSR. Like many large research holes, it had a series of offshoots from the central branch and the deepest, SG-3, was 7.6 miles (12,262 km) deep. The well reached this depth in 1981. The temperature at this depth was 356°F (180°C), at which point the rock became more like a plastic than a solid, halting further drilling.
Even though the hole in question was 7.6 miles (12,262 km) deep, it only penetrated a third of the Baltic continental crust. The rock at the bottom of the hole was about 2.7 billion years old, and the samples brought up from the bottom have contributed invaluably to the study of the geology and geophysics of the time. The original depth goal was 9.32 miles (15,000 meters), but a faster-than-expected temperature rise forced the project to be terminated prematurely. Had the hole extended to the expected depth, the expected temperature would have been 572°F (300°C), well above the maximum operating temperature of the drill.
The Kola Superdeep Borehole was the source of a tabloid rumor, started by a Finnish newspaper, that Russian researchers had penetrated all the way to hell. The story was reproduced by several American tabloids. He claimed that 9 miles (14.4 km) deep into the earth’s crust (1.4 miles (2.25 km) deeper than actual depth), scientists reached a pocket of air with a temperature of 2,000°F (1,093°C). Intrigued, they sent a heat-resistant microphone, which picked up the screams of the damned. The rumor was exacerbated when recordings of the alleged screams appeared on the internet soon after.
Several interesting discoveries have arisen from the hole. Pockets of water have occasionally been found, prevented from rising to the surface by a layer of impermeable rock. An excess of hydrogen was released from the drilling, which the researchers described as “bubbling” from the surface of the hole. More details about the geology of the Baltic shield have been discovered. This area was formed hundreds of millions of years ago when a supervolcano erupted and sent magma across a good portion of the continent.
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