Next time you are at the Mississippi Coliseum for a college basketball game, concert or rodeo remember that a half-mile beneath your feet is the vent of a volcano that has lain dormant for, by best geological estimates, some 70 million years.
David Dockery, state geologist and director of Mississippi Department of Environmental Quality Office of Geology, says that we don’t have much to worry about.
“It has been extinct for 70 million so the chance that it erupts is very slim,” he said.
“Slim” will probably convey different levels of comfort to different people, but the point is, Jackson erupting does not top the state geologist’s list of worries.
Research shows that some experts may have suspected a dormant volcano under Jackson in the early 1800s but we do know E.W. Hilgard was the first to publish the theory while he was doing a geological mapping of the Jackson area in 1860. Dockery said that the next time anyone uncovered evidence of a volcano was in 1930 when oil drillers drilled into igneous rock, rock formed by cooling magma.
Dockery said other signs have been observed that indicate volcanic activity including a magnetic anomaly and gravity anomaly meaning you “weigh a little more in Jackson.” Dockery said that this is no need to throw out your bathroom scale though because these anomalies are only detectable through sophisticated and sensitive devices.
“You probably wouldn’t see anything on your scale at home but with a magnetometer, you could pick up some differences or some of the instruments on a plane flying over might be able to detect the anomalies,” Dockery said.
Jackson does not have hot springs as a result of the vent, though, he said warm well water is not hard to find. Jackson’s water is provided by an aquifer that usually comes out between 80 and 90 degrees Fahrenheit. He said that water has been drawn as hot as 102 degrees and that some deeper wells dug into the gas rock have contained 128-degree saltwater. For reference, a hot water heater maintains a temperature of about 120 degrees.
There are actually two vents under Jackson, according to Dockery. The one at the coliseum is the most prominent but Clinton resident beware, there is also one right under the Jackson-Clinton line.
He said these are part of a cluster of volcanic vents. Dockery says that much of Mississippi was part of a seaway that stretched northwest possibly reaching as far as Alaska. During the Cretaceous period (between 145 and 66 million years ago) this seaway was dotted with volcanic islands. The Jackson Dome would have been one of them, likely inhabited first by flying dinosaurs or Pterosaurs known as Pteranodons. Dockery said it was probably about 420 square miles at its largest.
Dockery said it was likely part of a cluster or chain that includes four other volcanic vents in Washington and Humphreys counties and across the river near Monroe, Louisiana. The one in Humphreys is known as the Midnight Volcano named for the nearby town of Midnight, which recorded fewer than 200 residents in the 2010 census.
Dockery said the first time it hit the popular consciousness was in 1997 when some reports from the state and seismic information recorded by Exxon made it to the desk of Bruce Reid at the Clarion-Ledger. The Ledger printed a story by Reid on January 17, 1997, and Marshal Ramsey drew a volcano-themed political cartoon in the next day’s issue. Reid’s story was reprinted several times throughout the state and would boil back to the top of the local news cycle in a number of television and radio reports in February and April of that year signaling the release of disaster blockbusters “Dante’s Peak’ and “Volcano,” respectively.
In an article authored by Dockery and two of his colleagues at the Mississippi Office of Geology, John Marble and Jack Henderson, published that September offered a characteristically shaky assurance that the volcano would not erupt.
“The volcanoes of the northern Gulf Province have been silent for some 65 million years or more,” they wrote. “There is no reason to believe that any of them will ever erupt again.”
The following sentence starts with a “however” that feels like it should have been printed in all caps.
“HOWEVER (our emphasis), there is no more reason to believe they will not.”
The article goes on to ensure Jackson about how special it is.
“No other capital city or major population center is situated above an extinct volcano,” they wrote.
Various lists online place about 30 to 40 cities worldwide in close proximity to, but not on top of, volcanoes of various sizes and activity. In the United States, you have Honolulu, which is on an island formed by the nearby Diamond Head volcano. Portland and Bend, Oregon, are also close to volcanoes. Dockery says perhaps the closest similarity to Jackson is the extinct volcanoes Arthur’s Seat and Castle Hill close to, but not under, Edinburgh, Scotland.
