Earth's heat warms water of Bath County

JMU geologists are turning up new data about a long-appreciated natural phenomenon—the warm and hot springs of Bath County, Va.

Date published: 11/9/2009

WARM SPRINGS—For 250 years people have come to this place, stripped down to bathing clothes or bare skin, and lowered themselves into soothing pools of hot chemicals.

They’ve come to “take the cure” by drinking and immersing themselves in the naturally steaming, faintly smelly waters of Bath County.

That warm brew is laden with minerals. And its source is generally thought to be “meteorological”—that is, rainwater that soaks deep into the Earth, where it’s heated by geothermal forces.

But new research at James Madison University’s Department of Geology offers an additional explanation.

Last fall, associate professor Steve Baedke and then-undergraduate Nick Silvis took several samples of the thermal waters of the geological region known as Warm Springs Valley.

Tests by Lawrence Berkeley National Laboratory in California showed traces of a rare helium isotope—a signature of water not from the top layer of the Earth, the crust, but from the middle layer, the mantle.

The mantle, a thick section of rock between the crust and the core, makes up about 85 percent of the Earth’s volume. It’s very hot, with a temperature range from about 900 to 7,000 degrees Fahrenheit.

The mantle water isn’t in the form we see at the surface, said another JMU geologist, assistant professor Anna Courtier. Instead its hydrogen is structurally bound to the mantle rock.

It’s not fully understood how that rockbound water is freed to begin its upward journey through the crust. It could happen because of a gradual chemical process, or because of a geologic event that releases bursts of heat sufficient to melt even the highly pressurized mantle rock.

Baedke and Silvis presented evidence of mantle-fingerprinted Bath County water at a geology conference in Portland, Ore., just last month.

Though preliminary, the findings suggest a couple of possibilities, Baedke said.

Maybe the mantle in that area is closer to the surface than elsewhere on Earth. Or maybe more water is contained in the mantle than previously thought.

Once water is freed from the mantle, it moves upward through cracks and pores, traveling through the layers of sedimentary rock that make up the crust.

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Date published: 11/9/2009