What is the deepest man-made hole on Earth?

The deepest man-made hole on Earth is the Kola Superdeep Borehole, which reached 12,262 metres beneath Russia’s Kola Peninsula.

The Soviet Union began drilling the scientific project in 1970 to study Earth’s crust, rather than to extract oil or gas. Engineers drilled several connected boreholes, with the deepest branch reaching its maximum true vertical depth in 1989. The site is near the borders of Norway and Finland, in the far northwest of Russia.

The project produced surprising geological results. Researchers found water deep within fractured granite and did not encounter the basalt layer they had expected from seismic interpretations. Temperatures also became far higher than predicted; near 12 kilometres down, they approached 180°C, making further drilling technically difficult.

Drilling eventually ended in 1995 after funding problems. The Kola borehole remains the deepest hole measured vertically, although a later oil well in Qatar became longer when measured along its curved path. The Mariana Trench is far deeper than Kola, but it is a natural ocean trench, not a human-made hole. Bingham Canyon Mine is an enormous open-pit excavation, while Woodingdean Well is a much shallower hand-dug well.