The day that doomed the dinosaurs
Using rock samples extracted from deep beneath the Gulf of Mexico, scientists have created a detailed sequence of events of the most calamitous day for life on Earth, when a 6-mile-wide asteroid smashed into the planet 66 million years ago and brought an end to the age of dinosaurs. The geologic account was unearthed by an international team that used a drilling rig to tap into the heart of the asteroid’s crash site—the 125-mile-wide Chicxulub crater off Mexico’s Yucatán Peninsula. The extracted cores show that hundreds of feet of sediment built up rapidly after the impact, reports The Wall Street Journal. “We have [430 feet] in a single day,” says study co-leader Sean Gulick, from the University of Texas at Austin. “We can read it on the scale of minutes and hours.” The strike itself blasted a cavity in the ocean floor some 20 to 30 miles deep and sent a colossal plume of lava into the air, creating a peak higher than Mount Everest. It collapsed within minutes, pushing out huge waves of lava that solidified into a ring of peaks. Seawater began washing over these peaks some 20 minutes later, blanketing them in impact rocks and shards of volcanic glass. Finally, backwash from the megatsunamis triggered by the impact added more finely graded debris. That included charcoal, evidence of great fires sparked on nearby landmasses by the heat of the asteroid strike. The sediments suggest the blast also blew hundreds of billions of tons of sulfur from crushed ocean rock into the atmosphere, blocking off the sun and causing a global winter that would kill off 75 percent of life on Earth. Further analysis of the rocks, Gulick says, will yield more insights. “The discoveries keep coming.”