The Kola Superdeep Borehole is the deepest hole in the world as of January 2021.

In 1970, Soviet scientists began drilling the Kola Superdeep Borehole in Murmansk Oblast, Russia in an effort to learn more about the Earth’s crust and also probably to one-up the Americans that abandoned their Project Mohole in 1966. The hole is about 7.5 miles deep with a tiny diameter of only 9 inches. As of January 2019, it is the deepest hole in the world.

Kola Superdeep Borehole in Murmansk Oblast

The Kola Superdeep Borehole in Murmansk Oblast, Russia.

In 1992, the drilling was stopped due to the scorching temperature in the hole. Scientists projected the temperature to be about 220 °F but found it was actually closer to 350 °F. Drilling any deeper was deemed unfeasible as the temperature at the 9-mile mark would get above 570 °F, at which the drill bit would no longer work. So what’s in the hole? First, there is a lot of water. Scientists speculate the water might have formed from oxygen and hydrogen atoms squeezed out of the rock minerals, but no one knows for sure. Second, there are plankton fossils as deep 4 miles down the hole. You can read about other interesting discoveries here.

For all the effort and years of work, the hole only went 0.2% of the way to the center of the Earth. The site has since been abandoned and is now welded shut and considered to be an environmental hazard.

  1. The Sakhalin-I Odoptu Well is about 200 feet longer, but not as deep.
  2. Hell is deeper than 7.5 miles. 🙂
  3. No one knows why or how plank fossils got so deep into the ground.

  1. – Drilling to the Mantle: 6 unexpected discoveries from the world’s deepest well
  2. – What’s Inside the Deepest Hole in the World?
  3. – Kola Superdeep Borehole

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