“The signature from the osmium isotope analysis and the relative proportion of the elements matched that previously reported in volcanic gases,” Sun said. It had to have been something happening on Earth. That meant the cooling could not have been caused by an extraterrestrial impact. The researchers determined the elements in the Texas sediments were not present in the correct relative proportions to have been added by a meteor or asteroid that impacted Earth. The analysis focused on difficult measurements at the parts per trillion on osmium and levels of highly siderophile elements, which include rare elements like iridium, ruthenium, platinum, palladium and rhenium. University of Houston scientists Brandon and doctoral candidate Nan Sun, lead author, accomplished the isotopic analysis of sediments collected from Hall’s Cave in the Texas Hill Country. “This period of rapid cooling is associated with the extinction of a number of species, including mammoths and mastodons, and coincides with the appearance of early human occupants of the Clovis tradition,” said co-author Michael Waters, Ph.D., director of the Center for the First Americans at Texas A&M University. The Earth’s climate may have been at a tipping point at the Younger Dryas, possibly from the ice sheet discharge into the North Atlantic Ocean, enhanced snow cover and powerful volcanic eruptions that may have in combination led to intense Northern Hemisphere cooling, Forman said. “The Younger Dryas, which occurred about 13,000 years ago, disrupted distinct warming at the end of the last ice age,” said co-author Steven Forman, Ph.D., professor of geosciences at Baylor University. The study indicates that the episode of cooling, scientifically known as the Younger Dryas, was caused by numerous coincident Earth-based processes, not an extraterrestrial impact. Prior geochemical evidence for a large meteor exploding in the atmosphere instead reflects a period of major volcanic eruptions.”Īfter a volcano erupts, the global spread of aerosols reflects incoming solar radiation away from Earth and may lead to global cooling post eruption for one to five years, depending on the size and timescales of the eruption. “Thus, the trigger for this cooling event didn’t come from space.
“This work shows that the geochemical signature associated with the cooling event is not unique but occurred four times between 9,000 and 15,000 years ago,” said Alan Brandon, Ph.D., professor of geosciences at University of Houston. The resolution to this case of mistaken identity recently was reported in the journal Science Advances. The evidence is buried in a Central Texas cave, where horizons of sediment have preserved unique geochemical signatures from ancient volcanic eruptions - signatures previously mistaken for extraterrestrial impacts, researchers say. Researchers say cooling 13,000 years ago is coincident with major volcanic eruptionĬontact: Terry Goodrich, Baylor University Media and Public Relations, 25įollow us on Twitter: Texas (July 31, 2020) – Texas researchers from the University of Houston, Baylor University and Texas A&M University have discovered evidence for why the earth cooled dramatically 13,000 years ago, dropping temperatures by about 3 degrees Centigrade.
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