The Kola Superdeep Borehole is the deepest hole ever dug by humans. It’s located on the Kola Peninsula in northwest Russia, near the border with Norway. Russian scientists began drilling in 1970 to learn more about the Earth’s crust. They reached a depth of about 40,230 feet (12.2 km), deeper than Mount Everest is tall! But the hole is very narrow, only about 9 inches wide.
During the project, scientists made some surprising discoveries. They found extremely high temperatures (around 180°C), water trapped deep inside solid rock, and learned that the Earth’s crust is much more complex than they thought. They also found tiny fossil remains about 2 billion years old.
The drilling stopped in 1992 because the heat was too intense. The equipment at the time couldn’t go any deeper.