Meteor impact may have triggered massive Grand Canyon landslide 56,000 years ago

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A meteorite impact thousands of years ago may have triggered a landslide in the Grand Canyon and reshaped the Colorado River that runs through the national park.

Geologists studying driftwood and lake sediments found in Stanton's Cave — in Marble Canyon, which lies in the eastern part of the Grand Canyon — revealed a possible connection between the area and the famous impact site known as Meteor Crater (also called Barringer Crater) in northern Arizona.

Through excavation and multiple rounds of radiocarbon dating, researchers determined the driftwood is about 56,000 years old. Yet today, the mouth of Stanton's Cave sits 150 feet (46 meters) above the Colorado River. A new study suggests the wood was carried there by an ancient paleolake, formed when a massive landslide dammed the river.

"It would have required a 10-times-bigger flood level than any flood that has happened in the past several thousand years," Karl Karlstrom, co-lead author of the study and an Earth and planetary science professor at the University of New Mexico, said in a statement from the university.

The study claims that the strike that created Meteor Crater could be linked to a paleolake — an ancient lake that existed in the past but has since dried up — in the Grand Canyon that formed at the same time. The impact would have generated an earthquake around magnitude 5.4 to 6, which could have sent a shock wave powerful enough to shake loose unstable cliffs in the Grand Canyon 100 miles (161 kilometers) away and trigger a massive landslide. That event, in turn, could have deposited enough debris to dam the river and form a lake.

Other caves high above the river have also been explored for clues about the canyon's geological past. In addition to the driftwood, ancient beaver tracks have been found in areas that would be inaccessible to the water-dwelling animals today, further supporting the idea that a paleolake once existed in the area.

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With driftwood and sediment samples found in many caves as high up as 3,084 feet (940 m), the researchers estimate the paleolake would have been about 50 miles (80 km) long and nearly 300 feet (91 m) deep. Over time, the dam that blocked the Colorado River could have been overtopped and deeply eroded, eventually filling up with sediment.

While there is evidence linking the paleolake, the meteorite impact and resulting landslide, the researchers noted that further study is required to eliminate any other possible explanations for the river damming, such as random rockfall or a more local earthquake around the same time.

Their findings were published July 15 in the journal Geology.