Scientists now have strong evidence for one of geology’s longest-running debates about how exactly the Grand Canyon came to be.
A collaborative study led by the U.S. Geological Survey suggests that spillover flooding from ancient Lake Bidahochi, a large body of water fed by the ancestral Colorado River, played a central role in carving the canyon and establishing the river’s modern course.
Researchers from the USGS, the Arizona Geological Survey, UCLA, and Paradise Valley Community College analyzed mineral grains preserved in ancient lake deposits east of the canyon. By comparing the ages of those grains to sediments from early Colorado River deposits, the team pinpointed exactly when Colorado River material first reached the Bidahochi Basin, located east of Flagstaff, Arizona, primarily on Navajo land. The findings were published in Science.
“The evidence points clearly to a Colorado River-fed lake that could have spilled westward, establishing the river’s course through what is now the Grand Canyon. It’s a simple but powerful explanation for how the Colorado River system took shape.” – Ryan Crow, USGS geologist and lead author.
According to the study, beginning around 6.6 million years ago, sand within lake deposits shows a distinct Colorado River signature. Roughly two million years later, the river system had fully integrated, connecting Rocky Mountain headwaters all the way to the Pacific through the Gulf of California and carving the Grand Canyon along the way.
The research also acknowledges that multiple natural processes, including lake spillover, river incision, and shifts in regional topography, likely worked together to produce the canyon’s modern form.
Scientific discussion about Grand Canyon’s formation dates to 1869, when John Wesley Powell, who later became the second director of the USGS, first navigated the Colorado River by boat.
