SAN FRANCISCO — Drillers accidentally hit a pocket of molten rock underneath a working geothermal energy field in Hawaii, a lucky break for geologists that could allow them to map the geological plumbing that created everything we know as land.

The unprecedented discovery could act as a "magma observatory," allowing scientists to test their theories about how processes transformed the molten rock below Earth's surface into the rocky crust that humans live on today.

"This is like Jurassic Park for magmatic systems," said Bruce Marsh, a geologist at Johns Hopkins University. "You can go to museums and see dinosaur skeletons. But if a paleontologist could see a dinosaur frolicking in the open countryside, it would be absolutely spellbinding. And this is what it is for me to see this thing in in its natural habitat."

Scientists know a lot about lava, but far less about its subsurface predecessor, magma, the molten material that originates deep in the crust and cools into rock near the surface, sometimes erupting as lava. They've developed models of magma's behavior based on how recently created land looks, but they've never glimpsed the stuff where the vast majority of it actually resides, underneath the crust that covers the globe. Understanding magma and how it forms land could shed light on how our continents came to be composed the way they are.

"This is how we built the Earth," Marsh said. "We built the Earth from very primitive materials, materials that remelted and remelted and distilled and eventually you get continental material."

"It's exciting," said geologist Peter Kelemen of the Lamont Doherty Earth Observatory at Columbia University. He agrees that a live magma chamber could reveal some fundamental things about how crust is formed.

Because this is the first encounter scientists have had with underground magma, they are still putting together plans for how to best study it. They will likely drill more holes into the chamber and send instruments down to take measurements of size and characteristics.

"We don't really understand how the chemical differentiation of magma occurs," he said. Some theories suggest the separation of buoyant and non-buoyant material is responsible for creating different types of crust, a process that would be dependent on convection.

"The subsurface magma chamber could be convecting," Kelemen said. "That would be interesting."

Previously, the closest scientists have been able to get to magma has been in Hawaiian lava lakes. But the magma becomes stagnant and cools. The magma in the chamber is insulated from the air, and geologists will be able to study it in action.

Like so many other discoveries in the history of science, this one was an accident and completely unexpected.

One day in 2005, a commercial geologist was boring a hole deep into Hawaii's crust, looking for a place to inject waste fluid from the Puna Geothermal Plant back into the Earth. It was a routine process; the company had spent months drilling into basalt. As per their standard operations, the engineer sent the drill bit crunching through some more rock, pulled back and then went to reset the bit to drill deeper. But something strange had happened.

"My colleague called me as soon as he saw it. He's a very experienced geologist and as soon as he saw it, he knew immediately that we were into something very different, especially the way it behaved coming up the wellbore," said Bill Teplow, a consulting geologist with U.S. Geothermal. "The driller can actually feel it. He pulled the drill string up and when he set it down, he didn't set down on bottom, he set down 30 feet up."

The geologist re-drilled the hole several times with the same result. When they looked at samples of the rock, it wasn't the gray basalt that looks like cooled lava, it was clear and glassy.

"This is a singular event," Marsh said. "It's first contact with the inner Earth where the magma lives."

In this case, the body of magma is sitting underneath a standard geothermal field, with all of the geological tools — like massive drilling rigs — that can aid their quest.

"This could be the first magma observatory in the Earth," Marsh said.

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*Image: flickr/casch52

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