What is the Deepest Hole Ever Drilled?
The deepest hole ever drilled is the Kola Superdeep Borehole, on the Kola peninsula in the northwest corner of Russia, located near Finland. It was drilled for scientific research by the USSR. Like many large research boreholes, it had a number of offshoots from the central branch, and the deepest, SG-3, was 12,262 meters (7.6 miles) deep. The borehole reached this depth in 1981. The temperature at this depth was 180°C (356°F), at which point the rock became more like a plastic than a solid, stopping further drilling. Even though the borehole in question was 7.6 miles 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 samples brought from near the bottom contributed invaluably to the study of geology and geophysics at the time. The original depth goal was 15,000 meters (9.32 miles), but a faster-than-expected increase in temperature forced a premature halt to the project. If the borehole had extended
