Nevada Is Home To One Of World's Largest Asteroid Impacts


Wikimedia Commons

Distorted limestones from the Alamo impact in the Irish Range, Nevada.

When we hear about asteroids, it’s usually in movies where they’re speeding towards Earth, about to obliterate humanity.

But is that realistic? Turns out, it kind of is.

Benjamin McGee is a scientist with the Nevada National Security Site.

“There is a difference between is it realistic and is it likely,” he said.

McGee said researchers are tracking large asteroids or planet killers like the one Ben Affleck and Bruce Willis had to conquer in the movie "Armageddon."

He said scientists have tracked 90 percent of the asteroids that are bigger than a kilometer across, or about 0.6 miles. 

“Those are the ones that could really cause global destruction,” he said.

But McGee said we shouldn't worry too much because besides being tracked, the number of asteroids is limited.

“So every asteroid impact is an asteroid used up," he said. "There’s not infinite ammunition.”

However, if one of those large asteroids did threaten the earth, McGee said scientists are working on ways to prevent global destruction, including a plan to use the gravitational pull of a large spaceship to pull the asteroid off course, or to use a satellite to hit it hard enough to move it off course. 

Part of the second plan could involve using nuclear weapons, which McGee finds intriguing.

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“If we used it literally to try and smack an asteroid hard enough to shift its orbit, we’ve just turned a weapon of mass destruction into a weapon of mass salvation, which I think is awesome!” he said.

While the idea of smacking a large asteroid off course sounds fascinating, McGee said its the little asteroids that are a bigger threat because they are more plentiful and harder to find.

“The things going through our fingers right now are still big enough to level a town,” he said.

One asteroid about 60 feet across nearly landed outside a Russian town called Chelyabinsk in 2013. It exploded about 10 miles above the earth in the atmosphere, but it still blew out windows and damaged buildings on the ground.

McGee said the earth, like the moon, is covered in craters, but the evidence has been washed away.

“The reason we don’t see it on earth is because there is so much active erosion and wind and rain, it buries all that stuff,” McGee said.

Ground zero for one of the largest craters in the world is believed to be just outside of Alamo. Appropriately enough, it's called the Alamo Impact.

McGee said the impact happened about 400 million years ago, which is long before the asteroid that is believed to have killed the dinosaurs hit the earth.

He said the crater left behind is about 100 miles wide. “It would have caused widespread devastation,” he said. 

At the time of the impact, Nevada was a coastline, so the impact would have caused a massive tsunami. McGee said scientists have found evidence of the tsunami in the Las Vegas valley.

“That’s the problem of reconstructing this is that the rocks are so old. They’re jumbled. They’re fractured. They are buried," he said. "There are only a few spots where nature has brought them back up to the surface.”

One of those spots is at the top of Frenchman's Mountain on the valley's eastern edge. McGee said they've found tsunmanite, which are rock deposits caused by tsunamis. Those deposits are the same age as the rocks found in the asteroids crater.

“That was devastating enough to create a tsunami that raked across to where Vegas is right now,” McGee said. “It would've been a really bad day.” 

There is one problem with exploring the Alamo Impact: a large section of it is on the old Nevada Test Site, known today as the Nevada National Security Site.

McGee finds it interesting that we created craters with nuclear weapons on the site of one of the largest alien craters in the world.

Because of the restrictions on the site, researchers have only been able to study the part of the crater that is in Nye County, which is why McGee said researchers are skeptical.

"If you’re proposing a 100-mile wide crater, you need a lot of data to back it up... and right now we’ don’t have all of it," he said.

But he hopes scientists could one day be allowed in to research the area currently in the test site.

National Asteroid Day

Saturday, June 30 at 2:30 p.m.

National Atomic Testing Museum


Benjamin McGee, scientist, Nevada National Security Site

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