The U.S. government conducted more than 1,000 nuclear tests, most of them in the Nevada desert or on faraway Pacific islands, but it also set off a couple nukes under Mississippi:
In 1959, the American physicist Albert Latter theorized that setting off a bomb in an underground cavity could muffle the blast. After tests with conventional explosives, Latter wrote that a detonation as big as 100 kilotons—more than six times bigger than the bomb dropped on Hiroshima—“would make a seismic signal so weak it would not even be detected by the Geneva system.” His theory, known as “decoupling,” became a rallying point for people who wanted to keep testing, says Jeffrey Lewis, of the James Martin Center for Nonproliferation Studies in Monterey, California.
“They wanted to come up with a reason that we couldn’t verify an agreement with the Soviets,” says Lewis, who’s also the publisher of the Arms Control Wonk blog. But in 1963, after the Cuban Missile Crisis brought the world nose-to-nose with the unthinkable, the superpowers signed the Limited Test Ban Treaty. It kept future tests underground, and researchers turned to making sure those tests would be spotted.
The Atomic Energy Commission wanted to test Latter’s theory using actual nukes. And salt deposits were considered the ideal places for tests, since they could be excavated more easily than rock and the resulting cavity would endure for years. So the search was on for a salt dome in territory similar to where the Russians tested their bombs, Auburn University historian David Allen Burke says.
“It had to be a certain diameter. It had to be a certain size. It needed to be a very large salt dome that was still a distance underground and not where it could interfere with water or petroleum or anything else,” says Burke, who wrote a book about the Mississippi tests.
That led the agency to southern Mississippi, which is full of salt domes. The government leased a nearly 1,500-acre patch of forest atop one of those domes and got to work.
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The first blast, code-named Salmon, was a 5.3-kiloton device that would blow a cavity into the salt dome half a mile underground. The second, Sterling, was only 380 tons, and would go off in the cavity left behind by Salmon. AEC crews drilled a 2,700-foot hole down into the salt dome, lowered the first bomb into it, plugged it with 600 feet of concrete… and waited.
The Salmon test was put off nearly a month by a string of technical problems and bad weather, including Hurricane Hilda, which hit one state over in Louisiana. People living up to five miles from the test site were evacuated and recalled twice in preparation for blasts that never happened. They got paid $10 a head for adults and $5 for children for their trouble.
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Far from Latter’s predictions that a blast as big as 100 kilotons could be kept off the scopes, Lewis says, it turned out that decoupling “is not a worry for anything but a very small explosion.” However, the data helped shape a later treaty which limited underground tests to 150 kilotons.
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Federal records now indicate cancer rates in Lamar County are lower than both the state and national average.
(Hat tip to Hans Schantz.)