A breathtaking wonder in the landscape of North America, the Grand Canyon has been a center of attention among the scientific community for its mysterious geological history.
In a recent breakthrough, scientists are now discovering the precise timeline of how the Colorado River first began its longing for the region.
To reconstruct the river’s history, researchers analyzed microscopic clues hidden in the canyon’s layers. The clues consist of resilient mineral crystals called zircon grains, which are made up of river-borne sediments and ash particles from long-ago volcanic eruptions.
“Scientists have long debated when the Grand Canyon was carved out, and our study adds to that conversation,” said UCLA geologist John He, co-lead author of the study.
According to findings published in the journal Science, the river’s evolution began about 6.6 million years ago when it began flowing into a large depression, called a basin, in the Earth’s surface, leading to the formation of a wide and shallow lake to the east of the future Grand Canyon.
As the lake’s volume increased, it eventually bottomed out on the coast about 5.6 million years ago.
This flood sent a powerful wave of water across the landscape, effectively starting the formation of the Grand Canyon, the researchers found.
The river’s journey continued as it filled and flowed through a succession of Grand Canyon basins. It finally reached the Gulf of California about 4.8 million years ago and emptied itself into the sea.
But the lake called Bisahochi Lake that was formed at the site of the Grand Canyon is long gone.
“A long-standing question is: Where did the Colorado River go before it flowed through the Grand Canyon?” said co-lead author Ryan Crow, a research geologist with the US Geological Survey in Flagstaff, Arizona.
“We have long known that the river existed in western Colorado 11 million years ago, and that it only flowed through the Grand Canyon 5.6 million years ago. But until now, we knew almost nothing about where it was in the intervening time,” Crow said.
