Original photo by Sean Pavone/ iStock

At first glance, Jackson, Mississippi, is like any other state capital, with its domed capitol building standing squarely in the heart of the city. However, 2,900 feet below the surface lies a surprising secret — an ancient volcano. Although the West Coast and Hawaii are the U.S.’s biggest volcanic hot spots, millions of years ago active volcanoes also dotted the northern Gulf of Mexico region. One of these volcanoes was the Jackson Volcano, and the city’s Mississippi Coliseum now sits above its ancient crater. Thankfully for the city’s residents, the volcano is extinct and hasn’t erupted since around the age of the dinosaurs.

Over the past 12,000 years, the U.S. has had the most active volcanoes of any country.

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With its West Coast located along the Ring of Fire, and Hawaii resting on top of a volcanic hot spot, the land within today’s U.S. borders has experienced the most volcanic activity during the current Holocene Epoch. However, Indonesia has experienced the most activity since 1950.

The Jackson Dome formed in what’s known as the Mississippi Embayment, a sedimentary basin that was an extension of the Gulf of Mexico coastal plain, around 70 million years ago. Despite being buried by layers of rock due to various geographic transformations over millions of years, the volcano’s presence is still felt in surprising ways. Because of the dense igneous rock of the volcano, gravity is slightly stronger in the area, making Jacksonians heavier than their fellow Mississippians. And while Jackson is the only capital city set atop a volcano, volcanic formations can also be seen within the limits of other U.S. cities, including Portland, Oregon, and Honolulu, Hawaii.

Numbers Don't Lie

Numbers Don't Lie

Percent of the Earth’s surface that is volcanic in origin
80
Year geologist E.W. Hilgard discovered the extinct volcano beneath Jackson
1860
Registered members of the Choctaw Nation (Indigenous to the Jackson area)
212,000+
Years the volcanoes of the Northern Gulf, including Jackson’s, have been silent
65 million

“Mississippi,” a French derivative of the Ojibwa tribe’s name for the river, means “______.”

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“Mississippi,” a French derivative of the Ojibwa tribe’s name for the river, means “Gathering of Waters.”

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Volcanoes caused the most severe extinction event in Earth’s history.

Some 252 million years ago, an event known as the end-Permian extinction, or “the Great Dying,” killed nine out of every 10 living species on Earth. The change to the planet was profound: The event spelled the end of the 47 million-year-long Permian geologic period, cleaned the terrestrial slate, and allowed reptiles to evolutionarily outpace protomammals to become the new dominant life-form on Earth — dinosaurs. Although a variety of things likely coalesced to kick-start the Great Dying, one key culprit took place in an area known today as the Siberian Traps, a hilly region in northern Russia. Beginning around 252 million years ago, this region erupted continuously for 2 million years and covered 2.7 million square miles in lava. The volcanoes also pumped a massive amount of carbon dioxide into the atmosphere, causing a runaway greenhouse effect that led to hotter temperatures and increased ocean acidification. Scientists estimated that at one point during this extinction event, ocean water near the equator reached hot-tub-level temperatures of about 104 degrees Fahrenheit. Today, the dramatic activity that took place in the Siberian Traps is the largest known volcanic event of the past 500 million years.

Darren Orf
Writer

Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.