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Drilling Through The Earth’s Crust

By James Donahue

The task sounds simple enough. A team of European scientists report in the magazine Nature that they intend to drill a hole through the Earth’s crust and into the mantle.

Dr. Damon Teagle from the National Oceanography Center, Southampton, and Dr. Benoit Ildefonse, Montpellier University, France, say they want to drill a five-mile deep well through the crust and into the mantle. They say, however, that they don’t expect the technology or the money to finance the project to be available until about 2018.

It appears that Doctors Teagle and Ildefonse have been unaware of the Chikyu Hakken mission, a half-billion dollar effort by the Japanese, United States, European Union and China to poke a seven kilometer hole into the mantle. The project was planned for this year from the Chikyu, an ocean going vessel designed solely for the Chikyu Hakken mission that was launched in Japan in 2002.

Unfortunately, the Chikyu was moored in the port of Hachinohe, Japan, when the massive earthquake and tsunami struck on March 11. The Chikyu immediately evacuated the port but not before suffering some damage. Consequently the Chikyu Hakken mission has been cancelled for now.

Ironically, the purpose of the Chikyu Hakken mission was to acquire specimens from inside the mantle and try to gain a better understanding of the mechanisms of change that cause earthquakes and other geological events that affect the global environment.

While scientists appear anxious to drill through the planet’s crust and find out what exists in the mantle, they already appear to know a lot about what is down there. The official word is that the mantle is a complex, rocky, and very hot shell about 1,800 miles thick that surrounds an iron-rich hot core. Deep into the mantle the heat is so intense it is believed that the rock is partly melted, which may account for plate movements at this depth.

The crust, which is an ultra thin cover surrounding the mantle, ranges from five to 75 kilometers in thickness. Researchers have found that the crust is much thinner at deep parts of the world oceans. At one area on the Atlantic seafloor, between the Cape Verde Islands and the Caribbean Sea, the mantle lies exposed with almost no crust covering. 

The newly launched British research vessel James Cook visited this exposed area of the Earth’s crust in March, 2007, but the ship was not equipped with drilling equipment and could not take samples of mantle material.

One earlier attempt to bore into the mantle, known as Project Mohole, was abandoned in 1966 after repeated failures and cost over-runs. The deepest penetration was about 590 feet below the sea floor from the ocean drilling ship JOIDES Resolution.

So what lies in the mantle that attracts scientific teams to making all of this effort to get samples? It is believed that the rock formations at that depth differ in mechanical characteristics and chemical composition. Acquiring samples might give researchers some understanding as to why there are constant shifting of plates causing earthquakes, and why the planet endures unexpected volcanic activity.

The problems connected to drilling into the mantle involve the extreme heat generated from that deep in the Earth. Deepwater oil drillers have had to develop special drilling equipment that will withstand temperatures reaching 500 degrees Fahrenheit and extreme pressure in the rock formations.

Indeed, oil well drillers for Chevron’s Cajun Express rig bored the deepest known well in the world in 2007 when they reached an oil field under the Gulf of Mexico at five miles down. British Petroleum plans to drill up to seven miles deep under the Arctic Ocean perhaps this year.

If not drilling into the mantle, these super oil drilling operations must be getting very close to it.