The Sedan Crater


In our previous investigation, we learned a bit about the Nevada Test Site, thanks to an assist from Stranger Things.

There, the U.S. military tested over a thousand nuclear weapons in the middle of the uninhabited desert. Though atmospheric experiments led to mushroom-cloud tourism in Las Vegas, more than 90% of the devices detonated at the site blew up underground.

What happens when massive, atomic weapons explode in a subterranean fashion? As we approach the fireworks holiday of Independence Day 2022 here in the United States, let’s examine the case of a really big bang.

As the immediacy of the first decade of the Cold War passed without worldwide annihilation, nuclear researchers turned to experiments involving matters other than deterrence, defense, and armageddon.

Project Plowshare, begun at the end of the 1950s, sought to test the usage of nuclear explosives for the utility of peaceful construction. How can the most prominent bombs on the planet – designed to deconstruct – become ironic tools for construction? Operation Storax consisted of 47 nuclear shots with the aim of testing the capability of nukes to “build” things such as canals or bays. Construction by excavation!

On 6 July 1962 (our publication date is just five days short of the 60th anniversary), officials unleashed the Sedan Shot at Area 10 of Yucca Flat at the Nevada Test Site. This discharge left a lasting impression. 

The Sedan shot of Operation Storax - National Nuclear Security Administration

Scientists placed the 468-pound warhead into a shaft 636 feet below the surface. The explosion pictured above occurred despite the detonation happening over a tenth of a mile underground!

Sedan packed a serious wallop: the equivalent of 104 kilotons of TNT. A dome of earth elevated over 300 feet in the air during the first three seconds. At that point, the enormous weight of soil could not contain the nuclear blast, which vented the dome. The result was a displacement of more than 11 million tons of desert. Scientists likened the dispersal of the soil to a pyroclastic surge from a volcano, similar to the one that obliterated the areas surrounding Mt. St. Helens. The blast was so powerful that the ground could not be seen from the air in a circle around Yucca Flat with a diameter of 5 miles. If the event had been an earthquake, the temblor would have registered 4.5 on the Richter Scale.

When the dust settled – in this case, not a cliched metaphor – a gargantuan hole remained. The crater is 320 feet deep and 1,280 feet across!

The Sedan Crater - National Nuclear Security Administration
Observation decks at the Sedan Crater - photo by Jarek Tuszyński

Based on the Sedan Crater, nuclear weapons seem to be a good candidate for certain large-scale construction projects. Think cuts through mountain ranges for railway or highway projects. But there was one major issue.

What started underground near Vegas didn’t stay underground near Vegas.

Radioactive fallout from the Sedan blast spread quickly across the United States. The U.S. Department of Health and Human Services ranks the Sedan bomb as second on the list of events from the Nevada Test Site in spreading radioactive exposure. Approximately 7% of all the exposure experienced by Americans from the tests at the site came from just this one explosion. 13 million people suffered exposure, more than any other test.

The fallout did not merely affect those in the Nevada vicinity, either. Iowa took the brunt of the radioactivity, but counties across the nation registered fallout.

U.S. counties affected by fallout from the Sedan shot - National Cancer Institute

Unsurprisingly, the public fallout from the radioactive fallout put an end to the notion of using atomic devices in civil excavation. The United States quickly abandoned this line of experimentation.

That decision seems wise. To this day, the native, perennial shrubs of the Nevada desert have never grown back at the Sedan Crater.

Despite that apocalyptic fact, radiation levels dropped quickly. Within seven months, researchers could walk the crater safely. Today, approximately 10,000 people visit Sedan Crater each year on tours of the Nevada Test Site.

Check out this incredible footage of the blast, in which you can see the earth dome burble before the explosion annihilates it:

Further Reading and Exploration

Sedan Crater – U.S. Geological Survey

Sedan Nuclear Crater – Amusing Planet

Declassified U.S. Nuclear Test Film #30/Sedan Test – U.S. Government Film

Sedan Crater Virtual Tour – All Around Nevada

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