The borehole into the magma chamber took nearly five months to drill, and required the use of 25 hardened steel and tungsten carbide drill bits. Getting there "is a rare opportunity to calibrate geophysical measurements with direct observations of real rocks," says geophysicist Doug Wilson of the University of California at Santa Barbara, lead author on the Science Express paper. "Finding the right place to drill was probably the key to this success."

Wilson and his IODP colleagues found that place by identifying a region of the Pacific Ocean that formed some 15 million years ago when the East Pacific Rise was spreading at a "superfast" rate of more than nearly 8 inches per year, faster than any mid-ocean ridge on Earth today.

"We planned to test the idea that magma chambers should be closest to the Earth's surface in crust formed at the fastest spreading rate," says Wilson.

"These results confirm ideas about the way in which fast-spreading oceanic crust is built," says Jamie Allan, IODP program director at the U.S. National Science Foundation, which co-funds the program. "This new understanding opens the way to understanding the origin of oceanic crust, which we can best do by deep drilling."