The Colorado River’s Ancient Pathway: New Insights into an Age-Old Mystery
Geologists have long been intrigued by the Colorado River’s historical trajectory before it carved the renowned Grand Canyon. The river’s ancient course has puzzled scientists, who knew it flowed near Grand Junction, Colorado, about 11 million years ago and emerged from the Grand Canyon around 5.6 million years ago. However, its route during the intervening period remained a mystery.
A recent study published in Science sheds light on this enigma, suggesting that the river once pooled into a lake in the Bidahochi Basin on the Navajo Nation. This lake eventually spilled over the Kaibab arch, leading to the formation of the Grand Canyon.
Ryan Crow, a research geologist at the U.S. Geological Survey, emphasizes the significance of this finding. “Our new study has shown, I think pretty conclusively, that indeed these lake deposits east of Grand Canyon on the Navajo Nation were deposited by the Colorado River,” he states. Crow believes this spillover theory is the most plausible explanation for the river’s transition to its present course, which over millions of years, carved out the Grand Canyon.
This research is pivotal for future studies concerning the proto-Colorado River. As Crow notes, “Our ideas about the Grand Canyon are constantly evolving. I think our new work shows that this lake has to be incorporated into any kind of new models about how the river and the canyon formed.”
John Douglass, a coauthor of the study and professor at Paradise Valley Community College, acknowledges the longstanding debate over the canyon’s formation. While some theories posited an older canyon existing 15 million years ago, Douglass challenges this notion. He visualizes the process simply, likening it to filling a backyard hole with water until it spills over, carving a new path. “That’s fundamentally all that happened,” Douglass explains, emphasizing the study’s conclusion that the Colorado River reached just east of the Grand Canyon prior to its creation.
Back in the Bidahochi Basin, the environment during the initial spillover was likely water-rich. Crow describes it as “a lush environment, lots of animals, fish, mammals, birds, kind of congregating in this wet area in the desert.” This event was pivotal in transforming the Colorado River into the vast waterway that now supports millions amid ongoing drought conditions.
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