It is the deepest man-made hole on the planet - but after boring deep down into the earth, Russia was eventually forced to seal it up.

The digging originally came about due to Cold War rivalry. As well as competing in the space race, the Americans and Soviets also wanted to get closer to the centre of Earth, which resulted in the vast drilling competition to discover the secrets believed to lie there that could give information about the beginning of life itself.


The Deep-Drilling Race
Project Mohole aimed to retrieve a sample from Earth's mantle by drilling the ocean off Guadalupe Island, Mexico. The Americans drilled 601 feet (183 metres) into the seabed but the project was pulled in 1966.

The Soviets' attempt in Murmansk, Russia was known as the Kola Superdeep Borehole and dug much deeper into Earth and gathered samples that still impress scientists. Scientific drilling expert Dr. Ulrich Harms said the reason for the delving so deep into the earth was "to address key scientific questions" and to provide answers to biggest mysteries about our planet.

The Kola Superdeep Borehole didn't reach beyond the Earth's crust, but it still remains the deepest hole ever dug.


^{_{The Kola borehole is the deepest manmade hole ( Image: Wiki Commons)}}


The Kola Borehole's depth
It is the deepest hole in the world and deeper than Mount Everest is tall. Hidden in an abandoned drill site, it is virtually invisible from ground level, measuring just 9 inches (23 centimetres) in diameter.

But the borehole runs about 40,230 feet (12,262 metres) or 7.6 miles (12.2 kilometres) into Earth's surface. The deepest artificial point is impressive, but shallow compared to Earth's depth. It only penetrates a third of Earth's crust.


^{_{Scientists found temperatures higher than expected deep below the earth's surface ( Image: Wikipedia/Andre Belozeroff)}}

Drilling began at Kola on May 24, 1970 with the aim being to go as deep as possible. And by 1979 it had broken all world records at 6 miles (9.5 kilometers). It reached a depth of 40,230 feet (12,262 meters) in 1989 and became the deepest point ever reached.

Why drill so deep?
Holes are also dug in the name of science, Harms says, to better understand things such as earthquakes and volcanic eruptions and geothermal heat and energy. Another reason for going so deep was to find out about the evolution of life and to discover about environmental changes in the past to better predict the future.


^{_{Kola Superdeep Borehole is situated in Murmansk, Russia, but has now been closed off ( Image: Getty Images)}}

Harms says: "One example in detail is that observations very close to an earthquake zone allow [researchers] to monitor the initiation and propagation of even the tiniest earthquake in response to stress and strain. We want to recover these near-field physical, chemical, and mechanical data to fundamentally understand these processes that cannot be simplified in lab experiments or computer models."


^{_{The Kola Superdeep borehole was dug between 1970 and 1992 ( Image: Wikimedia Commons)}}