The Kola Trench, known for many years as the deepest trench on Earth, is 12,262 metres below the Earth's surface. This pit leading to the centre of the Earth is a man-made pit.

Don't let its depth frighten you because it is impossible for a person to fall into it. Because this pit is 23 cm in diameter. Dug over 20 years, this hole was made for scientific purposes. The researchers initially set the hole at about 14,500 metres. But then they changed their minds and planned to make the hole "as deep as possible". However, scientists and engineers encountered something unexpected during the work. The researchers faced high temperatures as the hole got deeper, so they decided to abandon the project.

12,000 metres below the surface, 2.7 billion-year-old rocks reached temperatures of about 180 degrees Celsius. This temperature was much higher than scientists had anticipated. These high temperatures deformed drill bits and pipes, making excavation work very difficult and costly. Therefore, scientists, who could no longer cope with the heat, put an end to the excavation work.

Scientists observed that the deeper they went, the softer the rocks became. Russian scientists in Kola stated that the rocks at these depths are more like plastic rather than rock. For scientists expecting to encounter a hard rock, these soft rocks were a surprising surprise.

Work on the pit was halted in 1992 and the project site was abandoned ten years later. The Kola Superdeep well continued to hold the title of the world's deepest pit until May 2008, when the 12,289 metre borehole drilled at the Al Shaheen oil field in Qatar took the record from Kola. Today, the 12,345-metre offshore oil well near the Russian island of Sakhalin holds the title.

 

Source: https://www.scientificamerican.com