The Deepest Hole in the World

Кольская сверхглубокая скважина

The Dead Sea in Israel is the world's lowest point below sea level. However, its 1,385-ft depth is minuscule compared to the deepest hole in the world. Mt Everest in Nepal is the highest point on Earth. However, if you took its 29,030-ft height and put it down the deepest hole in the world, it would not reach the bottom. The Mariana Trench in the Western Pacific Ocean is the lowest depression of the surface of the Earth's crust. The lowest point of the Trench is 36,200 feet below sea level. As you might be able to guess by now, the deepest hole in the world is even deeper than the Mariana Trench.

In 1962, the Soviet Union began the Kola Superdeep Borehole in Kola Peninsula, near Finland. The plan was to dig a hole into the ground as deep as possible for scientific research. Drilling didn't actually begin until 1970.

When the 9-inch-wide hole reached about 22,000 feet (4.2 miles), the scientists were amazed to find microscopic fossils of plankton. At these levels and even deeper, water was also discovered. This is water that has never been to the surface; it's created by the forcing together of hydrogen and oxygen molecules through the great pressures in the earth at those depths.

By the time the drilling was halted in 1994, the hole was about 40,000 feet deep -- 7.6 miles. To provide some aspect to this distance, if a person dropped a stone down the hole, it would take 50 seconds to hit bottom, not accounting for air resistance. The stone would be traveling 1,090 MPH upon impact, which is faster than the speed of sound, so it would actually create a sonic boom. In fact, the sound of the impact would take an additional 37 seconds to travel back to the surface -- so the person who dropped the stone would not hear anything for 1 1/2 minutes. 

[Update: I was too lazy to account for Terminal Velocity (objects can't freefall by gravity alone faster than 150 MPH in a vacuum -- 118 MPH with wind resistance). I've felt guilty for this lapse, so after some research, it seems that it would actually take an object about 220 seconds to hit bottom -- and no sonic boom will occur (although that would have been cool). The echo of the impact still would take about 37 seconds to reach the surface, so the stone dropper would have to wait about 4:17 minutes to hear the echo.]

So, why, after 24 years of drilling, did they stop drilling? It turns out that the temperature at the 40,000-ft. level reached 356°F (180°C). The rocks at that pressure and temperature become so soft and pliable that the walls of any hole became unstable and would continually collapse. It is a bit like trying to maintain a hole in very thick oatmeal. So, until new drilling techniques can resolve this problem, the present depth is likely to remain as is.

The drilling rig is maintained within a 200-ft. tall enclosure. Photos of this enclosure are incredibly dull and boring, so for the accompanying photo, I selected a hole from some other project in Russia. It is the Mirny diamond mine in eastern Siberia. It is 3,900 feet across at its opening, but a mere 1,772 feet deep. I think you'll agree that this photo is a lot more impressive than a gray cement tower surrounded by some rocks and scattered snow. Also, you might not have read the blog today if not for the photo -- so this was just a classic example of misdirection, a well-known Soviet manipulative method, by the way.