For years, people in Concord have heard tale that the city is built on a volcano. An ancient volcano, actually, that once spewed molten lava across the prehistoric piedmont.
One WFAE listener, Ben Kesterson, wrote to FAQ City wanting to know if the story is just an urban legend, or if there's any truth to it.
Kesterson, who grew up in Concord, said he probably heard the story first as a young kid on the bus, and when he would visit the S&D Coffee on U.S. 29, which has an impressive view of the Charlotte skyline.
"All the kids would say, 'Well, you can see that because we're at the top of the ancient volcano looking down into Charlotte,'" Kesterson said.
He said he also heard teachers talking about it in school -- not as part of a course, but in conversation -- which also seemed to lend credibility to the tale.
More recently, he was back at that coffee shop as an adult, and his husband, who is not from the area, remarked on the beautiful view of the skyline. Kesterson relayed the story of the underground volcano to his partner, "and he hasn't stopped making fun of me since that point," he said.
So, Kesterson wants to know if any of this is true, or at least enough to tell his husband, "I told you so," or if he's the victim of a really great small-town legend that's just a lot of bunk.
A Blast From The Past?
Turns out variations of this story have been going around for decades. The earliest reference this reporter could find was an article printed in 1985.
It was in a business magazine for the now-defunct Concord Telephone Co., and it told the story a little differently from Kesterson. It claimed Concord isn't on a volcanic mountaintop, but actually in a volcanic crater about 22 miles in circumference.
The Charlotte Motor Speedway was said to be in the center of this hollow, according to a later article by The Charlotte Observer, and some residents feared it might one day reawaken "with an earth-shaking roar" and deluge the countryside with flaming, molten lava.
In order to separate the fact from fiction, I reached out to two geologists with UNC Charlotte, who agreed to help set the record straight.
400 Million-Year-Old Magma
The first, Andy Bobyarchick, says he had heard this legend before, and whenever people ask him about it, he tells them: "You're not entirely wrong, but you're not entirely right either."
Bobyarchick says it is true that there's a pool of ancient, hardened magma directly beneath Concord, but he points out that's different from a volcano.
He explains it this way: "If you were here 400 million years ago, there would have been volcanoes on the surface. That surface now would be a few miles over our heads."
Imagine there's three or four miles of rock above where you are right now. There's a few volcanoes up there, and the bases of those volcanoes are surrounded by the ocean.
The east coast back then was somewhere in Tennessee, says Valerie Reynolds, also with UNC Charlotte. The only land out here was a number of tropical volcanic islands that formed a long chain from what we'd now think of as Georgia all the way up to New England.
All those volcanoes were fed from giant pools of liquid magma, slowly swirling a few miles beneath the earth's surface.
Over millions of years, those underground pools of magma cooled and hardened into solid rock, then stuck around as the top layers of the earth eroded away.
Now, in present day, those hardened pools of magma have reached the surface, and geologists say Concord is sitting squarely on top of one. It's named the Concord Pluton.
Bobyarchick showed me a map produced by the U.S. Geological Survey, which outlines the pluton's boundaries. It shows a purple blob encirling most of Cabarrus County, cutting across U.S. 29, swinging around Harrisburg and neatly looping back around most of the county. The purple blob, Bobyarchick says, is the 400-million-year-old magma.
The Geological Survey says it's probably Cabarrus County's most striking feature. It makes the area stand out because all that hardened magma is resistant to erosion. So while the surrounding land has eroded down, Concord has remained on what's now a circular chunk of higher ground. That's why you can get great views of Charlotte there.
Magma, Yes. Volcano, Maybe.
Bobyarchick says if there ever was a volcano here many millions of years ago, it's all eroded away now. Some researchers have speculated that perhaps the pool of magma under Concord may have once fed a volcano in this area, but Bobyarchick says it doesn't seem likely.
A professor and student at the Unversity of Tennessee studied the Concord Pluton's geochemistry and weren't convinced the magma fed into a volcano, and a graduate student at UNC Charlotte also looked at the data and came to the same conclusion.
They all think this pool of magma was probably just that -- an underground pool of magma that never shot up to the surface. The studies weren't entirely conclusive, however, and Bobyarchick says more research is needed before we can say for sure.
If you want to see some of the ancient magma on the surface, it's not too hard to find. Valerie Reynolds with UNC Charlotte says you can see it simply by taking a drive through Concord or Harrisburg.
Most of the boulders in the area - "they're usually black and white, usually about half-and-half, or you might see something a little bit darker in color," she says - are remnants of the ancient magma.
Some of the area's more prominent magmatic rocks are near the old Stonewall Jackson reform school. Look closely and you'll see they're composed of large rock crystals, which means they crystallized from magma many years ago.
That kind of magma-turned-rock also goes by another name: granite. That sounds less exciting, but the key is to remember these rocks took hundreds of millions of years to cool and form and get here. You could say they're Concord's oldest residents. And we owe it to them for our knowledge of what the world was like here 400 million years ago.
"It looks just like a simple rock," Reynolds says, "but it's really this amazing piece of history."
In conclusion, the legend of the Concord volcano is about half-true. Yes, the town is uniquely built on an ancient pool of hardened magma, but no, that's not the same thing as a volcano.
But you wouldn't be so far off if that's the story you tell.
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