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Science & Nature • Geology

Kola Superdeep Borehole

The Kola Superdeep Borehole SG-3 was a Soviet scientific drilling project on Russia’s Kola Peninsula.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

The Kola Superdeep Borehole SG-3 was a Soviet scientific drilling project on Russia’s Kola Peninsula. It reached a maximum depth of 12,262 metres in 1989, making it the deepest human-made hole on Earth. The project was intended to study the Earth’s crust and yielded important geological data before drilling ended in the early 1990s.

Background

The borehole was drilled by Soviet scientists as part of a major geoscience project to study deep crustal structure. Unlike oil and gas wells, it was intended primarily for basic scientific research.

Depth record

SG-3 reached 12,262 metres in 1989 and remains the deepest borehole ever drilled by humans. It is also widely described as the deepest artificial point on Earth.

Scientific findings

The project produced unexpected results, including evidence of unusual deep-crust conditions and microscopic fossils reported in ancient rocks. These findings influenced later ideas about crustal composition and deep geology.

End of drilling and site status

Drilling ended in the early 1990s after technical difficulty, especially high temperatures at depth, made further progress impractical. The facility was later dismantled and the borehole was sealed.

Key facts

  • Drilling began in 1970 as a Soviet scientific project to investigate the Earth’s crust.
  • The borehole reached 12,262 metres in 1989, setting a depth record that still stands.
  • It is located on the Kola Peninsula near Russia’s borders with Norway and Finland.
  • The project did not reach the mantle as originally intended.
  • Drilling was stopped because of extreme temperatures and technical limits.
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Canadian context

Canadian geoscientists and educators often cite the Kola Superdeep Borehole as a landmark in Earth science and deep-drilling research, especially when discussing crustal geology and the limits of drilling technology.

Frequently asked questions

What is the Kola Superdeep Borehole?
It is a Soviet scientific borehole drilled into the Kola Peninsula for geological research, not for oil or gas production.
How deep did it go?
It reached 12,262 metres (40,230 feet) in 1989.
Where is it located?
It is in the Pechengsky District of Russia’s Kola Peninsula, near the borders with Norway and Finland.
Why was it drilled?
The project aimed to study the Earth’s crust and collect geophysical data from great depth.
Is it still the deepest hole on Earth?
Yes. It is still described as the deepest human-made hole on Earth.
Why did drilling stop?
Drilling stopped because extreme temperatures and technical limits made deeper drilling impractical.

References

  1. Wikipedia — https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole
    Supports: Location, drilling dates, maximum depth, and record status.
  2. EarthDate — https://www.earthdate.org/files/000/002/374/EarthDate_216_C.pdf
    Supports: Location on the Kola Peninsula and deep-drilling context.
  3. HowStuffWorks — https://www.howstuffworks.com/engineering/civil/kola-superdeep-borehole.htm
    Supports: Scientific purpose, drilling end, temperatures, and notable findings.
  4. Russia Beyond — https://www.rbth.com/science-and-tech/330958-russia-kola-borehole-deepest-hole
    Supports: Scientific purpose, site status, and sealing/abandonment.