Meteor strike may have triggered a landslide in the Grand Canyon some 56,000 years ago

Yahoo

6 days ago

GRAND CANYON, Ariz. - Two landmarks in the Desert Southwest may share a historic connection, unveiled in a study published in the journal Geology.
Researchers led by a team at the University of New Mexico suggest that a large meteor triggered a massive landslide in the nearby Grand Canyon, blocking the Colorado River and forming a 50-mile-long lake.
Evidence comes from decades of investigative work involving driftwood and lake sediments found in caves high above the river in the Grand Canyon.
So how did decaying wood make it to at least 150 feet above the surface of the water?
"It would have required a ten-times bigger flood level than any flood that has happened in the past several thousand years," Karl Karlstrom, the study's co-author, stated. "Or maybe they are very old deposits left as the river carved down, or maybe they floated in from a paleolake caused by a downstream lava dam or landslide dam."
Original carbon dating performed in the 1960s estimated that the wood was at least 35,000 years old, but modern technology provided a more precise estimate of around 55,600 years - a time period that matches a meteor strike estimated to have occurred between 53,000 and 63,000 years ago.
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The study suggests that after the meteor collision, a shock wave, resembling at least a magnitude-5.4 earthquake, loosened rocks and cliffs, creating a landslide that effectively acted as a dam for the Colorado River, which then formed a lake.
Based on aquatic sediments tested, researchers estimated the lake would have stretched about 50 miles and reached depths of at least 300 feet.
"The team put together these arguments without claiming we have final proof; there are other possibilities, such as a random rockfall or local earthquake within a thousand years of the Meteor Crater impact that could have happened independently," Karlstrom explained. "Nevertheless, the meteorite impact, the massive landslide, the lake deposits, and the driftwood high above river level are all rare and unusual occurrences. The mean of dates from them converge into a narrow window of time at 55,600 ± 1,300 years ago which gives credence to the hypothesis that they were causally related."
Over time, the dam that once blocked the Colorado River is thought to have eroded, and the massive lake has since dried up and filled with debris.
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Experts with the Lunar and Planetary Institute estimated that the size of the asteroid was likely in the ballpark of 100 to 170 feet across, which is large enough to destroy a community the size of Kansas City.
Researchers did not state whether other nearby rockfalls may be attributed to the meteor strike or whether they happened overtime through a more natural Earth-based process.Original article source: Meteor strike may have triggered a landslide in the Grand Canyon some 56,000 years ago
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