There may be a 60-kilometer-wide crater buried under Wyoming. WeekendReads
Some 280 million years ago, before the rise of the Rocky Mountains—or even the dinosaurs—a 2.5-kilometer-wide asteroid smashed into the supercontinent of Pangaea, near the eastern border of present-day Wyoming. The impact’s heat and shock wave would have killed anything within 400 kilometers, making it one of the largest asteroid strikes in North American history.
“This is a spectacular finding,” says Brandon Johnson, a planetary scientist at Purdue University unaffiliated with the study. “The work is rigorous and I’m convinced.” The crater field, he adds, which has 60 candidate holes that have yet to be confirmed, has the potential to represent 40% of the craters known on Earth.
Searching for alternative explanations, Kenkmann and his colleagues observed that many of the craters were elliptical. That’s unheard of for impacts from space, which tend to punch circular holes even when they strike at oblique angles because of their speed. And like blood spatter at a crime scene, the axes of these ellipses projected back to a common point.
Ancient Wyoming had other plans, however. These small cavities, created by boulders up to 8 meters wide falling at up to three times the speed of sound, contained quartz grains that originally formed from wet sand—indicating the boulders crashed into a quiet lagoon of some sort. The craters were soon entombed by hundreds of meters of silt, which turned into shale over the course of 200 million years.
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