An asteroid impact wiped out the dinosaurs

An asteroid impact wiped out the dinosaurs

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66 million years ago, aasteroid10 km in diameter impacted theYucatan peninsulain Mexico and wiped out most of the species on our planet by emitting a large amount of molten material and gases into the atmosphere and causing acid rain, acidification of the surface waters of the oceans and a sudden warming that lasted years. This was followed by a nuclear winter for decades.

However, scientists have not always agreed on the origin of the mass extinction of the dinosaurs. A part of the research community has supported that theintense volcanic activity produced by the impact in the area called traps by Decanin India it also contributed to the disappearance of fauna.

The experts thus discuss whether the volcanism occurred at the end of theCretaceous, coinciding with the extinction event known asK-Pg, or during the early Paleogene.

“The fact that there were two events of planetary importance that more or less coincide in time has created this debate about which of the two mechanisms caused the extinctions: if volcanism could weaken ecosystems and the impact of a meteorite gave the last lace or if it was only the meteorite ", clarifiesLaia Alegret, co-author of the study published nowScienceand paleontologist at theZaragoza's University.

After decades of controversy, the new work closes the debate by showing that volcanic activity did not play a direct role in the mass disappearance of the dinosaurs. According to the team led by theYale University (USA), the only cause was the asteroid.

"Thevolcanoescan cause mass extinctions because they release many gases, such as SO2 and the CO2, which can alter the climate and acidify the planet ”, he explainsPincelli hull, lead author of the work and professor of geology and geophysics at the American university.

However, the volcanic activity and associated warming occurred before and after the impact and not during the extinctions.

The new research shows that only theimpactthe asteroid coincided with the disappearances. Later, new volcanic phases slowed down the recovery of ecosystems.

Why did the volcanism not affect

“The volcanic activity in theCretaceouscaused an event ofgradual global warmingof about 2 ° C, but not a mass extinction, "says Michael Henehan, formerly at Yale University. "Several species moved towards the north and south poles, but they did so long before the impact of the asteroid," the expert details.

To reach these conclusions, the researchers analyzed soundings and outcrops from all oceans and latitudes, combined climatic, biotic and carbon cycle records obtained from sediments and marine fossils such as fish teeth and shells, and compared them with various scenarios oferuptions volcanic and impact.

The result was the creation of themore detailed reconstruction of global temperature of that period. "The models that best fit our temperature curve are those in which the main phase of volcanism occurred at the end of the Cretaceous and ended 200,000 years before the extinctions and the impact of the asteroid," adds Alegret.

The researchers thus demonstrate that most of the gas release occurred long before the impact of the asteroid, and that this was the sole driver of theextinction.

"A lot of people have speculated that volcanoes were important to K-Pg, and we're saying they weren't," Hull stresses. Furthermore, the scientists reject the hypothesis that massive eruptions occurred in the Deccan region of India after the extinction because "there is no matching warming event."

“The K-Pg extinction profoundly altered the global carbon cycle. These changes could allow the ocean to absorb a huge amount of CO2 over long time scales, perhaps hiding the effects of the warming of volcanism after the event ”, concludes Donald Penman, co-author of the work and postdoctoral researcher at Yale.

Bibliographic reference:

P.M. Hull et al. "On impact and volcanism across the Cretaceous-Paleogene boundary"Science January 16, 2020.

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