Book 24, Question 5
What is the deepest hole people have ever drilled?
The Kola Superdeep Borehole in northern Russia reached about 7.6 miles down, after drilling on and off for almost 20 years. That is deeper than the deepest spot in the ocean, which is about 7 miles down. Yet it is just a pinprick in Earth, which is almost 4,000 miles from surface to center. The drill stopped because the rock was hotter and softer than expected.
More fun facts
- The deepest hole people have ever drilled is the Kola Superdeep Borehole in the far north of Russia.
- It goes down about 40,230 feet, or 12.2 kilometers.
- Soviet scientists started drilling it in the Arctic Circle in 1970 and worked for almost 20 years.
- Even at its deepest, the drill was only about one third of the way through Earth's crust.
- Drilling stopped in 1992, when the rock temperature reached 180 degrees Celsius.
- A German project in Bavaria drilled a rival superdeep hole about 9 kilometers deep.
Sources: bbc.com
Questions kids ask
Why did they stop drilling the Kola hole?
The rock got as hot as 180 degrees Celsius, which made deeper drilling too hard.