An asteroid from space slammed into the Earth's surface 66 million years ago, leaving a massive crater underneath the sea and wreaking havoc with the planet.
No, it's not that asteroid, the one that doomed the dinosaurs to extinction, but a previously unknown crater 248 miles off the coast of West Africa that was created right around the same time. Further study of the Nadir crater, as it's called, could shake up what we know about that cataclysmic moment in natural history. Uisdean Nicholson, an assistant professor at Heriot-Watt University in Edinburgh, happened on the crater by accident -- he was reviewing seismic survey data for another project on the tectonic split between South America and Africa and found evidence of the crater beneath 400 meters of seabed sediment. "While interpreting the data, I (came) across this very unusual crater-like feature, unlike anything I had ever seen before," he said. It had all the characteristics of an impact crater. To be absolutely certain the crater was caused by an asteroid strike, he said that it would be necessary to drill into the the crater and test minerals from the crater floor. But it has all the hallmarks scientists would expect: the right ratio of crater width to depth, the height of the rims, and the height of the central uplift -- a mound in the center created by rock and sediment forced up by the shock pressure. The journal Science Advances published the study on Thursday. "The discovery of a terrestrial impact crater is always significant, because they are very rare in the geologic record. There are fewer than 200 confirmed impact structures on Earth and quite a few likely candidates that haven't yet been unequivocally confirmed," said Mark Boslough, a research professor in Earth and Planetary Sciences at the University of New Mexico. He was not involved in this research but agreed that it was probably caused by an asteroid. Boslough said the most significant aspect of this discovery is that it was an example of a submarine impact crater, for which there are only a few known examples. "The opportunity to study an underwater impact crater of this size would help us understand the process of ocean impacts, which are the most common but least well preserved or understood." The crater is 8 kilometers (5 miles) wide, and Nicholson believes it was was likely caused by an asteroid more than 400 meters (1,300 feet) wide hurtling into the Earth's crust. While much smaller than the city-sized asteroid that caused the 100-mile-wide Chicxulub crater that hit off the coast of Mexico that led to the mass extinction of much of life on the planet, it's still a pretty sizable space rock. "The (Nadir) impact would have had severe consequences locally and regionally -- across the Atlantic Ocean at least," Nicholson explained via email. "There would have been a large earthquake (magnitude 6.5 - 7), so significant ground shaking locally. The air blast would have been heard across the globe, and would have itself caused severe local damage across the region.DailyBangladesh/RAH Source: https://www.daily-bangladesh.com
