Scientists drill through unseen layer of Earth's crust

A team of American and Japanese scientists began drilling at the site--500 miles west of Costa Rica--in 2002, lured by theoretical predictions of thin crust in areas where the sea-floor spread most rapidly. More than 12 million years ago, this region of the Pacific formed new crust at nearly nine inches per year--faster than any spreading occurring today. Because of that quick spreading, the underlying layer of gabbro--coarse-grained, black volcanic rock--should be nearer to the surface, explains team member Doug Wilson, a geophysicist at the University of California, Santa Barbara. "If that theory were to be correct then we should only need to drill a relatively shallow hole compared to anywhere else," he says.