The Kola Superdeep Borehole is the world’s deepest human-made hole. Located high up on the Kola Peninsula in Russia, near Finland, work began on the site in May, 1970. A Cold-War-era relic, the hole began as part of a reverse Space Race between the Soviets and the US to see who could dig the deepest into the Earth’s crust. Despite longer holes being drilled since then, the Kola Superdeep Borehole remains the deepest artificial hole on earth and in the process of drilling it, the Russians dug up more than they bargained for.
While U.S. deep-drilling efforts petered out due to lack of funds, the Russians dug away for 24 years, finishing up in 1994 with a system of holes, the biggest of which was 7.6 miles (40,230 feet, 12,262 meters) deep. This means the Kola Borehole runs about a third of the way through the continental crust. And as always when one boldly goes where none have gone before, there were some unexpected results. While the initial target depth of the hole was 49,000 feet (15,000 meters), drilling halted in 1989 when temperatures at the bottom of the hole reached 356°F (180°C), considerably more than the expected 212°F (100°C). With temperatures projected to reach as high as 570°F (300°C) at the target depth, further work was postponed and then canceled altogether because the drill would not be able to function at such extreme temperatures.
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In addition, core samples from the drill site revealed that the Earth’s crust was not actually composed as previously theorized. Under the Conrad discontinuity theory, geologists had expected to find a transition from granite to basalt rock at the point where the upper and lower layers of the earth’s crust intersect, about 23,000 feet down (7,000 meters). Instead, samples revealed nothing but granite until drilling ceased, much deeper than anticipated. Drilling also uncovered water at around 23,000 feet. Theoretically, this was not possible, but scientists hypothesized that this was due to oxygen and hydrogen atoms being forced together into water molecules due to the intense pressure at such depths, and then trapped by the rock layer above. The team also uncovered ancient microfossils of 24 different single-celled planktons, a fascinating discovery made all the more remarkable by the fact that the fossils were preserved in such extremes of heat and pressure.
While drilling was officially canceled at Kola in 1994 and the site now lies abandoned, the results of the project demonstrate that sometimes a bit of unhealthy competition can yield positive results.
Via Slate.com and Atlas Obscura
Photos by Bigest, Rakot13 and Andre Belozeroff via Wikimedia Commons