Science & Technology

You Can Still See the Destruction From America's Largest Asteroid Impact

Talk about destruction! Thirty-five million years ago, an asteroid slammed into the ocean near North America's East Coast, bringing a wave of troubles with it: fires, earthquakes, a tsunami, an air blast, and even blazing-hot droplets of glass falling from the sky like rain (remnants of which you can still see today). A new study shows just how devastating this event was, using fresh dating techniques on the region.

Slam Chunk

Asteroids are space rocks that are usually harmless. They're remainders of what the solar system looked like billions of years ago, before planets and moons formed. But occasionally, one of them gets off track and slams into Earth. NASA keeps an eye out for the biggest civilization killers and rest assured, the agency has found nothing imminent yet. But it has happened in the past — just ask the dinosaurs, who are believed to have been wiped out by an asteroid about 66 million years ago.

The new study, recently published in the journal Meteoritics & Planetary Science, concerns the Chesapeake Bay impact crater. This crater was buried for eons and only discovered in the 1990s thanks to a drilling project. It's a huge divot in the Earth, some 25 miles (40 kilometers) across. It's the largest crater in the U.S. and the fifteenth-largest in the world.

While the crater remains hidden, its evidence is far-reaching. After the asteroid hit, it threw off a huge layer of material that covers a zone about 10 times the size of Texas. This includes tekties — natural glass that forms after space rocks hit the Earth — and shocked zircon crystals. A science team examined drilling samples from the crater and dated them with a new technique for the first time, which helps narrow down exactly when the impact occurred.

Boundaries of the crater

Gazing Into Crystals

Most people think of zircon as a pretty gemstone, but there's more to this mineral than meets the eye. Preserved in the zirconium silicate crystals generated by this impact is an echo of the shock pressures and high temperatures that the space rock generated when it crashed into Earth. These crystals are also small and difficult to study since they are only about as thick as a human hair.

Scientists examined crystals found about 250 miles (400 kilometers) northeast of the impact site using a technique called uranium-thorium-helium dating. Radioactive elements such as uranium and thorium naturally decay into more stable elements over time — in this case, helium. Because the decay takes place at a predictable rate, scientists can precisely date samples by looking at ratios of the different elements contained within these samples.

The team studied 21 crystals and found a wide variety of ages, between 33 million and 300 million years old. However, the two youngest samples had an average age of 35 million years, which matches other estimates for when the Chesapeake Bay crater formed. So this is a solid confirmation of previous work using a different technique for dating the region's debris.

"Our results demonstrate the uranium-thorium-helium dating method's viability for use in similar cases, where shocked materials were ejected away from the crater and then allowed to cool quickly, especially in cases where the sample size is small," said lead author Marc Biren, a scientist at Arizona State University, in a statement.

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Learn about other devastating events in our planet's past in "The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions" by Peter Brannen. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Elizabeth Howell September 3, 2019

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