This Nevada Crater Was Made by a Nuclear Bomb & Open Via Monthly Tours

Sedan Crater, Nevada

The largest man-made crater in America sits in the middle of Nevada, and it took just one nuclear bomb to create it.

Operation Plowshare wanted to prove atomic weapons could move mountains and dig canals. Instead, they got a giant hole and a lesson in atomic overkill.

Here’s how this nuclear excavation happened, and how you can join a Sedan Crater tour.

Operation Plowshare Origins

Scientists started the Plowshare Program in June 1957 at Lawrence Livermore National Laboratory.

The Atomic Energy Commission, which later became the Department of Energy, approved the program to find peaceful uses for nuclear bombs. They named it after a Bible verse about turning weapons into farming tools.

Leaders hoped nuclear blasts could speed up major digging projects. One explosion might do in seconds what would normally take months with regular equipment.

The program focused on testing whether controlled nuclear explosions could create waterways, remove mountains, or help with mining.

The Nuclear Device Design

Engineers built the Sedan bomb differently from regular nuclear weapons.

The bomb used 70% fusion and 30% fission reactions. This mix would move more earth while leaving less radiation behind.

Though small in size at just 17 inches wide and 38 inches long, the 468-pound device packed tremendous power. It equaled 104,000 tons of TNT, about five times stronger than the Hiroshima bomb.

The design borrowed ideas from two earlier test bombs called Bluestone and Swanee that had been tested in 1962.

Preparing For Detonation

Workers dug a shaft 636 feet straight down into the desert at Yucca Flat.

The hole went through alluvium, the loose soil and sand that had built up in the desert basin over time. This spot would show how nuclear blasts affected common ground types.

This test used a bomb 3.5 times more powerful than any previous test at the Nevada site. Scientists wanted to prove that nuclear explosions could do real construction work.

The team calculated the perfect depth to place the bomb to make the biggest crater with the least fallout.

The Explosion and Dome Formation

The blast turned the flat desert into a scene of massive force.

When the bomb went off, it instantly vaporized the surrounding soil. The pressure pushed up a dome of earth 300 feet high, taller than the Statue of Liberty.

This huge bulge held for three seconds before breaking open. Twelve million tons of soil burst upward in a fountain of dirt that rose thousands of feet.

The blast caused shaking equal to a 4.75 earthquake that people felt hundreds of miles away.

Immediate Aftermath and Dust Cloud

Two huge clouds of dust and radiation shot up from the blast site.

One cloud reached 10,000 feet high while the other climbed to 16,000 feet. Winds pushed these clouds northeast and then east across the country.

A wall of dust, called a base surge, spread outward along the ground. This fast-moving cloud covered an area five miles across.

The explosion scattered earth over 2,500 acres, changing the landscape so much that it looked different from space.

Radiation Levels Post-Detonation

Right after the blast, radiation at the crater edge measured 500 roentgen per hour.

This level was deadly – anyone standing there would get a fatal dose in under an hour. No one could safely approach the new crater.

After 27 days, radiation dropped to 500 milliroentgen per hour – much lower but still unsafe for long periods.

Seven months later, levels fell to 35 milliroentgen per hour. Scientists could finally enter the crater without special suits to study its structure.

Nationwide Radioactive Fallout

The Sedan test spread radiation farther than any previous American nuclear test.

Wind carried radioactive dust thousands of miles, mainly into the central United States. Tests found high radiation in eight Iowa counties and parts of Nebraska, South Dakota, and Illinois.

About 13 million Americans were exposed to radiation from this single test – more than from any other U.S. nuclear explosion.

Sedan produced about 7% of all radiation that fell on Americans during four decades of Nevada nuclear testing.

Unprecedented Radioactive Release

Later studies showed Sedan released more radioactive material than any other U.S. nuclear test.

The blast scattered 880,000 curies of iodine-131, which can cause thyroid disease. For certain radioactive elements, this single test released more than all other American tests combined.

These materials included radioactive forms of gold, beryllium, molybdenum, and other elements that scientists tracked across the country.

Experts now believe that with better bomb design after 1965, the test might have caused 100 times less radiation.

End of the Plowshare Program

The widespread radiation from Sedan ultimately killed the entire Plowshare program.

Scientists found that using nuclear bombs for construction would spread dangerous radiation to populated areas. Any building benefits were far outweighed by health risks.

Public concern grew as doctors linked radiation to increased cancer. Political support quickly faded.

President Kennedy’s test ban treaty with the Soviet Union in August 1963 effectively ended the program, though a few more underground tests happened through the 1960s.

Environmental Recovery

Sixty years later, the crater remains a bare scar in the Nevada desert.

Tumbleweeds now grow inside the crater along with some desert grasses. These tough plants have moved into the disturbed soil as radiation has slowly decreased over decades.

A 1993 study found that none of the original desert shrubs had returned to the crater. The nuclear blast changed the soil so much that the native plants cannot grow back.

Visiting Sedan Crater

You can see Sedan Crater only through official tours of the Nevada National Security Site.

Tours depart from the Atomic Museum at 755 E. Flamingo Road in Las Vegas at 7:30 AM, returning around 4:00 PM. The Department of Energy offers these free monthly tours, but reservations fill quickly, often a year in advance.

Read More from WhenInYourState.com:

• The Nevada Museum Where Visitors Experience a Simulated Atomic Blast Inside a Recreated Test Bunker
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• Private: 10 Facts You Should Know About Nevada Desert’s Most Infuriatingly Mysterious Location