Virginia is for... volcanoes? Well, millions of years ago

From Virginia Pilot Online.com: Virginia is for... volcanoes? Well, millions of years ago
Virginia is known for many things, from its beaches to its mountains, its farms and universities.

But volcanoes?

True enough, Virginia has a quirky if still unexplained history with volcanic activity, one of the few East Coast states that can make that claim.

While many small fractures and cracks remain as evidence that lava once flowed freely millions of years ago, two ancient and prominent examples still can be seen today: Trimble Knob, in Highland County near the West Virginia line, and Mole Hill, near Harrisonburg.

They could not look any more different. Trimble Knob is small, stubby and nearly treeless; Mole Hill is taller, sprawling and covered by thick bramble and forest.

Mennonite farms, including horse-drawn carriages on country roads, lie at the foot of Mole Hill. Sheep graze atop Trimble Knob.

Both land features are what geologists call plugs, the slowly eroding remnants of extinct volcanoes. Here, black basalt rocks indicating their fiery origins can be found amid a sea of green sedimentary stones that otherwise dominate the Shenandoah Valley landscape.

Both are relatively young volcanoes, active between 38 million and 48 million years ago, making them the babies in any state east of the Mississippi River. And both are held by private landowners, which limits their access and keeps most tourists away.

Gerald Knicely in May bought a big chunk of Mole Hill, including access to the woody summit, and hopes to soon develop trails for mountain bikers and hikers. Knicely also owns Mole Hill Bikes, a cycling shop in the town of Dayton, within earshot of the dead volcano.

"I grew up here and have always felt a really strong connection to Mole Hill," he said recently at his office. "There's a spirituality about the place, a uniqueness. It's hard to explain."

Little scientific study of the two volcanoes has been done, though that is changing.

Elizabeth Johnson, a geology professor at James Madison University in Harrisonburg, has taken a keen interest in Mole Hill, which she can almost see from her campus office. She regularly shuttles her students there for field trips and research projects and has a friendly rapport with Knicely.

This summer, for example, several JMU students completed projects aimed at better understanding what lies beneath the ancient volcanoes. Using rock samples and mathematical models, the students determined the depths of the Earth's mantle below Mole Hill and how hot it must be down there.

The answers, they estimate, are 24.2 miles deep and 2,192 degrees Fahrenheit. Generally speaking, Johnson said, those numbers gradually get smaller toward the coast.

"It's the first time we've started to look closely at this site," Johnson said recently in her lab, where she was showing off thin slices of volcanic rock under a microscope while wearing a JMU Geology T-shirt. "I'd love to spend more time working on this. It's new, and the kids love to get out and see it first-hand."

While Johnson has visited Trimble Knob, she has not done serious field work there but definitely wants to, noting how it is younger than Mole Hill by about 13 million years.

The recent earthquake that shook much of the East Coast also has sparked new interest in seismic activity and volcanoes. Asked if the two state volcanoes could somehow become active again and erupt, Johnson paused.

"Well, they are extinct, and there's no reason to think there's magma being created there. So I'd say there's probably no effect to worry about. But stranger things have happened."

One of the mysteries of Mole Hill and Trimble Knob is what caused volcanic eruptions there. Scientists are simply not sure.

Volcanoes typically go off because of the constant rubbing and shifting and internal pressures of tectonic plates within the Earth. When a big slippage occurs in an active area, magma can be released and volcanoes often burst forth.

But 50 million years ago was not a time of major shifting and seismic activity in Virginia, leaving scientists to wonder what triggered the events in the Shenandoah Valley.

Theories abound, but the most commonly held one was developed by the U.S. Geological Survey in a landmark 1993 study. It speculates that a combination of factors, including a regional fracturing event in the valley, might have done the trick, creating a big enough crack to allow magma to flow upward toward the surface.

Applying this theory, scientists do not think the eruptions in Highland and Rockingham counties carried on too long in geologic time, perhaps a few millions years, according to a 2006 paper by the Virginia Department of Mines, Minerals and Energy.

"It's a hot-spot type of volcano," said Jim Beard, a geologist and the curator of earth sciences at the Virginia Museum of Natural History in Martinsville, who has written about Mole Hill. "No one's really sure why they erupted, or why they stopped."

The museum does not maintain an exhibit on Virginia's volcanoes, Beard said, though it once produced a traveling exhibit that eventually found a home at Virginia Tech.

Beard noted that a vast expanse of molten rock, called the Petersburg pluton, can be found within the James River. This material did not erupt, however; it is liquid rock that hardened beneath the Earth's surface, affecting parts of six counties and stretching more than 60 miles.

Most residents near Trimble Knob and Mole Hill simply shrug when asked if they know they are living next to a volcano.

"It doesn't bother me," said Doris Folks, deputy clerk of the court in Highland County, whose office is just blocks from Trimble Knob. Locals, she said, call it "Volcano Hill," adding that she has never been to the top in her life.

"Visitors will ask about that funny-looking bump, and I'll tell them it's a volcano," said Lisa Jamison, manager of the Highland Inn in Monterey, where Trimble Knob can nearly be seen from the front porch. "But they think you're lying to them."

Students at the Monterey elementary school visit the site for science class, Jamison said, but the volcano is not mentioned in any walking tours in town or in tourist pamphlets.

Pam Lambert lives at the foot of Trimble Knob, which rises about 200 feet above surrounding farmland. She can recall an Easter Sunday church service at the summit one year that was especially inspiring.

"I've always loved it," she said. "I wish they'd open it up and sell tickets. They'd make a fortune."

The volcano is owned by Lavinia Bird, who tolerates curiosity-seekers but is not thrilled at having trespassers on her farm. She declined to talk about Trimble Knob when contacted by phone, saying she doesn't know much about it.

Someone has built a small step ladder that jumps Bird's back fence and provides access to the knob. The volcano is covered by long, lush, reddish grass that ripples in a nearly constant breeze. The top provides breathtaking views of Monterey and the Appalachian Mountains around Highland County.

Little mounds of volcanic rocks are strewn about the summit, as if spit out onto the ground, but there is no visible hole where the lava came out; the mouth has long since eroded away.

Access to Mole Hill is restricted as well, though Knicely, the owner, will let most people visit if they sign a liability waiver at his bike shop.

Two paths lead up the hill through oak and paradise trees. They split and then reconnect near the top. Spider webs must be swept away to keep moving ahead, and one gets the feeling of embarking on an Indiana Jones excursion through some dense rain forest. A deer suddenly leaps nearby, crashing through the brush.

Halfway up, a cross has been erected to mark where a previous owner, Lowell Ulrich, died while clearing a path to the volcano for a church group. His tractor flipped and trapped him beneath, killing him on Sept. 25, 2008.

History texts say locals celebrated the conclusion of the War of 1812 with a barbecue on top of Mole Hill, where an ox was roasted.

Unlike Trimble Knob, there are no spectacular views at the summit. A dense canopy of trees makes it difficult to even tell you've reached the top, some 1,900 feet above sea level.

Butterflies dance through thickets of goldenrod, and volcanic rocks are tossed randomly about on the ground, some cracked open to show their tell-tale ebony interiors.

The going is easy back down Mole Hill, the trail looking familiar.

At the bottom, tractors are plowing fields and cars wind through two-lane roads. Civilization has been found, leaving only the round shape of a dead volcano in the rear-view mirror.