In April 2006, geologists reported that they had successfully drilled into the bottom layer of the ocean's crust for the first time—and so have come a step closer to understanding how the foundation of the world takes shape.
New crust forms at midocean ridges where the sea floor spreads apart. Lava leaking from the ridges creates the crust's upper layer; beneath that lies a second layer, composed of the fossilized channels that once piped molten rock to the ridges. The formation of the lowermost crust, made up of a dark, magnesium-rich rock called gabbro, is still largely a mystery, one that holds the key to the workings of the magma source that feeds the whole process.
Douglas Wilson, a geophysicist at the University of California at Santa Barbara, and his colleagues traveled 500 miles west of Costa Rica to an area of ocean floor that formed 15 million years ago. There they found just the right piece of crust—not too hot, not too thick, and not too crumbly—to drill down to the gabbro. In 2006 they released their findings: After drilling through nearly a mile of sediment and crust, they finally hit the gabbro layer for the first time. Wilson hopes to drill deeper into this third layer by 2009. Then he will truly plumb Earth's deep secrets.
Anne Sasso
The scientific research drilling ship Joides Resolution is exploring the hidden structure beneath the ocean's floor . |
http://www.discover.com/issues/jan-07/features/earth-science/?page=3#90
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