Science & Technology

Life Bounced Back Just a Few Years After the Asteroid Killed the Dinosaurs

There isn't really a great name for the asteroid that killed the dinosaurs — at least, not one that has stuck in the public consciousness. It's sometimes called the K–T extinction event, and the site of its impact is known as Chicxulub Crater off the Yucatan Peninsula. Good luck finding someone who knows either of those off the top of their head. It's strange since that's probably the astronomical event that most directly led to the evolution of humankind. Then again, maybe it wasn't that big of a deal after all. Sure, the dinosaurs didn't do so well after the asteroid hit, but it turns out that other forms of life were able to move right into the crater in a matter of years.

Deep Impact

Any time you talk about the age of the dinosaurs or its dramatic end, it can be easy to get tangled up in time scales. Don't make the mistake of lumping all the dinosaurs together into one group that all got wiped out at once. We've already told you how a T. rex with a shovel and chisel could have dug up a fossilized Stegosaurus — dinosaurs roamed the Earth for so long, many of them lived closer in time to us than to each other. Nowhere does that incredible sense of scale come into sharper relief than at Chicxulub Crater, where 65 million years ago, an era 180 million years long came to a screeching halt in a matter of minutes.

That asteroid impact and its climate-changing aftermath drove more than 75 percent of species on Earth to extinction. It immediately sent a 330-foot-tall wave crashing over what's now Mexico, Florida, and Texas, and marked the beginning of what might have been a decade of global darkness as the dust and ash gradually settled back to the ground. It was a Big Deal. But according to a new study, although dinosaurs felt that impact from all over the world, living things near the actual crater were able to move back in pretty shortly after the hubbub died down.

Don't get too excited — we're not talking about a "The Lost World"–style enclave of dinosaurs hidden at the bottom of the ocean. This is strictly life of the tiny-invertebrate variety. Paleoceanographer Chris Lowery examined cores of sediment taken from about 600 meters (1,968 feet) beneath the ocean floor at the site of the crater. These arm-sized tubes of limestone and other materials still bore the marks of the cataclysm, when mountains the size of the Himalayas rose and fell in an afternoon. But significantly, using equations to determine how fast particles settle in a liquid, Lowery and his team were able to say that the stone had found its ultimate resting place just a few years after the impact.

Oh, and that limestone? It was riddled with the fossils and burrowed tunnels of plankton, small worms, and tiny shelled creatures known as foraminifera. That's not normal — another crater, this one in the Chesapeake Bay, was bereft of all life for millennia afterward. So what made the K–T asteroid so deadly to dinosaurs and many other species, but comparatively easy on the tiny fauna of its immediate vicinity?

Location, Location, Location

The Chesapeake Bay crater is a bit smaller than the one in the Yucatan — 85 kilometers (53 miles) across compared to 180 (112 miles). But Lowery doesn't think size has much to do with it. Instead, it was the location of impact that made it easier for new life to make its way in. When the Chesapeake Bay asteroid struck, it immediately killed all of the fish, crustaceans, and other aquatic life in the area. The bodies of those animals then decayed as they were consumed by microorganisms. But as the organic matter decayed, it consumed the water's oxygen, leaving the area completely inhospitable to any kind of life. Only as erosion reconnected the crater with the larger ocean over time did bubbles of fresh air begin to dissolve into the water.

The Chicxulub crater, by contrast, was formed half-in, half-out of the Gulf of Mexico. Since the crater's northeastern side was immediately open to the water, the natural currents washed nutrient-carrying water through the area right from the beginning. With the Earth's natural spin-cycle clearing out the debris and reinvigorating the water with oxygen, life didn't have to wait long to move back in.

Okay, but what if there was a secret enclave of dinosaurs living at the bottom of the ocean, or at the center of Antarctica, or deep beneath the Earth? Read Sir Arthur Conan Doyle's "The Lost World" (or listen for free with your trial membership to Audible) for one of the most iconic examples of this Victorian adventure novel. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Reuben Westmaas June 27, 2018

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