The discovery of a large impact crater beneath the North Atlantic Ocean suggests that more than one asteroid could have spelled doom for the dinosaurs.
A newly discovered impact crater under the sea floor suggests that more than one asteroid hit Earth during the time of the dinosaurs’ extinction.
Scientists have discovered evidence of an asteroid impact crater under the North Atlantic Ocean. This could force researchers to rethink how the dinosaurs came to an end.
The team believes the crater was formed by a collision with Earth about 66 million years ago. This coincides with the Chicxulub asteroid hitting Earth off the Yucatan coast of present-day Mexico, wiping out the dinosaurs.
“It would have generated a tsunami over 3,000 feet high and an earthquake over 6.5.” — Veronica Bray
The crater, which is more than 5 miles (8 km) in diameter, was discovered using seismic measurements, allowing scientists to probe deep into the Earth’s surface.
Veronica Bray, a researcher at the University of Arizona’s Lunar and Planetary Laboratory, co-authored the study. Advances in science details of discovery. He specializes in craters found throughout the solar system.
Nadir Crater, named after a nearby seamount, is buried 1,300 feet (400 meters) below the sea floor about 250 miles (400 km) off the coast of Guinea, West Africa. According to the research team, the asteroid that created the newly discovered Nadir crater could have been formed by the breakup of the parent asteroid or by an asteroid swarm at that time. If confirmed, the crater would be one of fewer than 20 marine impact craters found on Earth.
Veronica Bray, pictured here visiting Meteor Crater in Northern Arizona, is a crater formation expert. Credit: Sarah Sutton/Lunar and Planetary Laboratory
What impact would an asteroid have?
Bray used computer simulations to determine what kind of collision occurred and what the effects might be. Simulations show that the crater was created by a 1,300-foot-wide (400-meter-wide) asteroid impact in 1,600-2,600 feet (500-800 meters) of water.
“It would have generated a tsunami over 3,000 feet high and a magnitude 6.5 earthquake,” Bray said. “Although this is much smaller than the global cataclysm of the Chicxulub impact, Nadir will have contributed significantly to the local devastation. If we have found a “sibling” to Chicxulub, that begs the question: Are there others?
The asteroid’s estimated size would put it roughly on par with it asteroid Bennutarget OSIRIS-RExUArizona leads[{” attribute=””>NASA asteroid sample return mission. According to Bray’s calculations, the energy released from the impact that caused the Nadir crater would have been around 1,000 times greater than the tsunami caused by the massive underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano in the Polynesian country of Tonga on January 15.
“These are preliminary simulations and need to be refined when we get more data,” Bray said, “but they provide important new insights into the possible ocean depths in this area at the time of impact.”
What does the crater look like?
The crater was discovered somewhat by accident by Uisdean Nicholson, a geologist at Heriot-Watt University in Edinburgh. He was examining seismic reflection data from the seabed during a research project dedicated to seafloor spreading, the geologic process that caused the African and American continents to drift apart, thereby opening the Atlantic Ocean.
“I’ve interpreted lots of seismic data in my time, but had never seen anything like this. Instead of the flat sedimentary sequences I was expecting on the plateau, I found an 8.5-kilometer depression under the seabed, with very unusual characteristics,” Nicholson said. “It has particular features that point to a meteor impact crater. It has a raised rim and a very prominent central uplift, which is consistent for large impact craters.
“It also has what looks like ejecta outside the crater, with very chaotic sedimentary deposits extending for tens of kilometers outside of the crater,” he added. “The characteristics are just not consistent with other crater-forming processes like salt withdrawal or the collapse of a volcano.”
The asteroid crashed around same time as the dinosaur killer
“The Nadir Crater is an incredibly exciting discovery of a second impact close in time to the Cretaceous–Paleogene extinction,” said study co-author Sean Gulick, an impact expert at the University of Texas at Austin. “While much smaller than the extinction causing Chicxulub impactor, its very existence requires us to investigate the possibility of an impact cluster in the latest Cretaceous.”
According to the seismic data, the sediments impacted by the asteroid likely correspond with the Cretaceous-Paleogene boundary – a sedimentary layer demarcating the end of the Cretaceous period and last known occurrence of dinosaurs. However, there is some uncertainty about the precise time of impact, limited by the resolution of the data.
“Despite 4 billion years of impactors hitting Earth, only 200 have been discovered,” Gulick said. “It is thus exciting news whenever a new potential impact is discovered, especially in the hard-to-explore marine environment.”
Nicholson has already applied for funding to drill into the seabed to confirm that it’s an asteroid impact crater and test its precise age.
Reference: “The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure” by Uisdean Nicholson, Veronica J. Bray, Sean P. S. Gulick and Benedict Aduomahor, 17 August 2022, Science Advances.
DOI: 10.1126/sciadv.abn3096
