How deep is the deepest hole drilled into the Earth? It is 7.5 miles or 12,262 kilometres. Where is it? It is in Murmansk, Russia. The Kola Superdeep Borehole, as it is known, did not get through the Earth's crust - it is 25 miles thick below the land. They wanted to drill 9 miles but discovered such intense heat, they stopped. This was in 1992. It took 20 years to accomplish this - to get about a third of the way through the continental crust.
The American effort started in 1958 off the coast of Mexico and was discontinued in 1966. They had reached only 183 metres. German scientists reached about 6 miles below the surface of Bavaria in the 1990s. They discontinued when they hit seismic plates and found temperatures of 600 degrees Fahrenheit. The Japanese drilled almost 2 miles into the ocean floor.
Below the crust is the mantle, and it holds the imprint of the geological record of the Earth's history. There were two-billion-year-old fossils from single-celled marine organisms at 4.4 miles down.
The Cold War competition between the US and Soviet Russia ran its course. No single country could take on the activity as costs spiralled with the need to invent technology to accomplish the task.
The effort now underway to reach the mantle is being led by the Center for Deep Earth Exploration, owners of the drilling vessel Chikyu. They expect the project to take dozens of years and one-billion dollars. The effort and funding is collaborative with Japan, US, European, China, Australia, India, New Zealand and Brazil participating.
What is the scientific prize they are seeking? “The ultimate goal of the [new] project is to get actual living samples of the mantle as it exists right now,” says Sean Toczko, programme manager for the Japan Agency for Marine-Earth Science.
“It’s the difference between having a live dinosaur and a fossilised dinosaur bone.”
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