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September 10, 2019 01:00 pm

Scientists Discover New Evidence of the Asteroid That Killed Off the Dinosaurs

An anonymous reader quotes a report from The Wall Street Journal: Drilling into the seafloor off Mexico, scientists have extracted a unique geologic record of the single worst day in the history of life on Earth, when a city-sized asteroid smashed into the planet 65 million years ago, wiping out the dinosaurs and three-quarters of all other life. Their analysis of these new rock samples from the Chicxulub crater, made public Monday, reveals a parfait of debris deposited in layers almost minute-by-minute at the heart of the impact during the first day of a global catastrophe (Warning: source paywalled; alternative source). It records traces of the explosive melting, massive earthquakes, tsunamis, landslides and wildfires as the immense asteroid blasted a hole 100 miles wide and 12 miles deep, the scientists said. The sediments also offer chemical evidence that the cataclysm blew hundreds of billions of tons of sulfur from pulverized ocean rock into the atmosphere, triggering a global winter in which temperatures world-wide dropped by as much as 30 degrees Fahrenheit for decades, the scientists said. "The asteroid blasted a cavity between 25 and 30 miles deep in the first seconds of impact, creating a boiling cauldron of molten rocks and super-heated steam," reports The Wall Street Journal, citing the scientists' interpretation of the rock. "Rebounding from the hammer blow, a plume of molten rock splashed up into a peak higher than Mount Everest. Within minutes, it collapsed into itself, splashing gigantic waves of lava outward that solidified into a ring of high peaks, the scientists said." "About 20 minutes or so later, sea water surged back over the newly formed peaks, covering them in a blanket of impact rocks, the scientists said. As minutes became hours, waves choked with shards of volcanic glass and splintered rock rippled back and forth, coating the peaks in a layer of impact rock called suevite, the scientists said. As the hours passed, the backwash of waves added more and more finely graded debris. At the very top of the rock core, the scientists detected traces of organic matter and charcoal." The study was published today in the journal PNAS.

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