In the late 1950s, a team of American and Soviet scientists began conducting experiments to penetrate the earth's crust. The Earth's shell is known to continue on its way into the mantle, which makes up 40% of the planet's mass.
In 1958, the US took the lead with Project Mohole. However, funding was stopped, the United States never made it to the Earth's mantle. However, the Soviets took over this project. Be the Kola hole, be the deepest hole the Earth has ever seen.
The research team carried out excavations in the Pechengsky District, Kola Peninsula, Russia. The goal is simple, they want to dig as deep as possible. On June 6, 1979, the Kola pit reached 39,000 feet or 11.8 km, nearly 12 km.
After successfully achieving this record, excavation was stopped. Kola has become a tourist spot and is growing in popularity, as reported by The Delite.
Finally, this experiment was carried out again, then it was closed due to technical problems, and was continued again and reached 12.2 km. However, before reaching the mantle, a problem arose and led the team to cancel further excavations.
In the first 10,000 feet (3 km), the temperature was within the expected parameters, but gradually increased in heat. After that point, the heat begins to increase at a much faster rate. As they neared their destination, the pit heated up to 180 degrees Celsius. It's 80 degrees hotter than expected.
It was also found that the rock at this depth was also less dense. Rocks that are 'more brittle' and higher temperatures cause strange reactions within the Earth's crust. Knowing that their equipment would not last long under these conditions, the Kola team abandoned the project. This happened in 1922, 22 years after drilling began.
Although drilling was forced to stop, scientists discovered an interesting fact about the so-called Kola Superdeep Borehole. Tiny marine plant fossils found four miles inside Earth. It's impressive how the fossils manage to stay intact, especially with the rock estimated to be over two billion years old.
In the end, the closing of the Kola Superdeep Borehole coincided with the fall of the Soviet Union. In 1995, the project was permanently closed. Since the drill hole was made, the record is unbeaten, Kola remains the deepest hole on Earth.