Earth Science - Other

Kola Superdeep Borehole

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The Kola Superdeep Borehole or SG-3 is located in the Kola Peninsula in the Soviet Union and it is the second deepest borehole on the planet. It was the deepest borehole until 2008, when it was surpassed in depth by the Maersk Oil & Gas hole in Al Shaheen off of Kahar. The Kola Superdeep Borehole was created under the steam of man's curiosity about what lies beneath the surface of our Earth. It is an amazing example of mankind's ingenuity and thirst for knowledge.

The USSR's Interdepartmental Scientific Council for the Study of the Earth's Interior and Superdeep Drilling began planning the monumental drilling project in 1962. The plan was to bore through the Earth's upper crust to study what lies underneath. In 1965 the council chose the Kola Peninsula as the site for their project. Over the next five years preparations for drilling were completed. A drill was specially designed for the project because no drills that were being used at the time would work for such a deep hole. The drill is housed in a 200 ft. tower at the site. It penetrated the soil of the Kola Peninsula in 1970.

Over the course of the next twenty-four years, several boreholes, that branched off from one another, were made at the site, but SG-3 was the deepest by far. Core samples from the hole were taken during the entire process and at each depth. These samples revealed a lot about the composition of the Earth's crust. A wealth of plankton fossils was even discovered, at depths of up to nearly 21,981 feet. Many of the discoveries that were made were completely unexpected, thus proving that we can really only guess at the unknown and oftentimes those guesses are incorrect.

The drilling of the Kola Superdeep Borehole ceased in 1994. The hole was still 1.7 miles away from the hoped for depth, but it had reached an astonishing 7.6 miles into the Earth. It is roughly nine inches in diameter. As the drill had gone deeper, the Earth had become hotter. This was to be expected, but the temperature was far higher than anyone had predicted. Experts believed that at a depth of 7.45 miles the temperature would be 212 degrees Fahrenheit. The temperature at that depth turned out to be 356 degrees Fahrenheit. Unfortunately, there was nothing that scientists at the time could do to regulate the heat enough to continue drilling. It is estimated that the temperature would have reached 572 degrees Fahrenheit if the drill had reached the projected depth.

The drill still stands to this day and the site is still useful for scientists. All of the core samples that were taken out of the hole are still being studied. The site is currently under the control of the State Scientific Enterprise in Superdeep Drilling and Complex Investigations in the Earth's Interior. It will be interesting to see if drilling will ever continue at the site.


Bellows, Alan, Marche 5, 2007, The Deepest Hole, retrieved 9/23/09,

Kola Superdeep Borehole, retrieved 9/23/09,

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