Magma Opus: Geologist Reveals Earth's Plumbing

November 12, 1998

Momentous Theory In Earth Science Topples

The chance find of large crystals in the rocks of the Dry Valleys of Antarctica has led to a startling discovery by a geologist from The Johns Hopkins University.

One of the fundamental principles of geology is about to topple.

Bruce Marsh, professor of earth and planetary sciences, has demonstrated that the long-held notion of giant subterranean chambers containing pure, crystal-free magma does not accurately portray the true underground systems that carry and process the primordial ooze shaping the Earth's crust.

Instead, Marsh is methodically reporting a stream of evidence showing that the planet's internal plumbing is comprised of a plexus of smaller vertical columns of interconnected sheet-like chambers that transport a magmatic mush replete with crystals previously formed and recycled.

"I think people are a little overwhelmed," said Marsh, who appeared recently on the pages of "National Geographic" magazine encamped with his students on the frigid, desolate sands of Antarctica. "Scientists have walked all over this area for 20 or 30 years, and now here comes this guy who flies in, digs around a little and starts saying, "Hey, do you guys know what we're looking at here? Do you know what this is? This is the Rosetta works!' But that is exactly where we are. We're on the crest. We're unifying the theory of magmatism."

The excitement radiating from his lab is only barely detectable in the series of brief scientific papers Marsh has written since 1993, when he first literally stumbled onto a scattered rubble pile in the Dry Valleys and experienced a sudden awareness that one of the primary ideas of his discipline was severely flawed.

The significance of his findings has the attention of the National Science Foundation, which now funds an assortment of carefully chosen field studies for Marsh in Canada, Iceland, and on the ocean ridges of the Atlantic and Pacific oceans. Supporting evidence continues to allow the geologist to chip away at sacrosanct ideas about Earth's underground terrain.

His work poses a critical challenge to a theory embedded in geological lore for the past one hundred years, which assumes that any body of magma begins its slow evolution to igneous rock singularly devoid of crystals, then begins growing crystals that eventually produce recognizable, intricate layering in the body. For more than 25 years, Marsh has been working to understand the deep underground systems that move magma into the Earth's crust. However, the effort to "get into the boiler rooms," as he says, has been particularly difficult because so little of it is actually visible.

"You find pieces of systems visible all over," Marsh said. "But most places only show you chunks of the system, like finding bits of a furnace strewn along the side of a road. You never see how, say, you hook the blower up to it or the fuel pipes and the electric lines and everything else. How does it all fit together? What's it look like when the whole system is connected? That's been one of the big problems."

In 1993, Marsh found his complete "furnace" exquisitely preserved, frozen in time, on a trip to the Dry Valleys of Antarctica. Lacking vegetation and insects, with very little weathering to strip away the evidence, the cold desert was the one place on Earth where large deposits of magma had been injected in long, layered seams called "sills," which ran for hundreds of miles and were visible to the naked eye.

It was an astonishing discovery.

He has been careful not to say too much about the work that is quickly overturning one of the fundamental ideas of the discipline. Altering the course of science must be done carefully and, at least initially, without a great deal of fanfare. The new foundation, he assures, is being laid out methodically and precisely.

"I've been cautious not to make this sound too dramatic. I'm not saying, "C'mon, guys, you're accepting a theory that's not accurate. You know what that means? It means you can take your old bag of beliefs and toss them out the window.' No, I just hope some of my colleagues will just be sitting at home one night with a glass of sherry, thinking, 'good god ...'"

With one of his next ventures back to Antarctica, Marsh said he hopes to take a team of scientists with him so they can see the evidence for themselves.
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Bruce Marsh home page:
National Geographic article
Journal of Petrology; April 1998

Johns Hopkins University

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