According to the study, the Colorado River followed a complicated path as it carved out the canyon, with help from ancient lakes.
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The sight awed a president. “Arizona has a natural wonder in the Grand Canyon that is absolutely unparalleled in any other part of the world,” President Theodore Roosevelt said after seeing the canyon in 1903.
“I’m not going to try to describe it, because I can’t. I couldn’t choose the words that would or could tell an outsider what that canyon was,” Roosevelt continued.
Stunning views overlooking the Colorado River, now at the bottom of the canyon, leave visitors amazed at when and how the river was created. A new study published April 16 in the journal Science offers one answer.
The Colorado River didn’t always flow through the Grand Canyon region, but it may have started flowing after an ancient lake flooded about 5.6 million years ago, according to the study.
The authors say their findings suggest that lake discharge was the primary process establishing the Colorado River’s flow path through the Grand Canyon, although other mechanisms such as groundwater flow or erosion may have played a supporting role.
But critics say the study provides more questions than answers. Karl Carlstrom of the University of New Mexico, an expert on Grand Canyon history, said the timing, location and evidence of a potential lake spill are still unknown.
“Therefore, important details of the proposed spillover conclusions remain untested by the data presented in the paper,” he said.
What’s new about this study?
A long-standing question has been: “Where did the Colorado River go before it flowed through the Grand Canyon?” said study co-author Ryan Crow of the U.S. Geological Survey.
He said scientists have long known that the river existed in western Colorado 11 million years ago and only emerged from the Grand Canyon after 5.6 million years ago.
“But until now we know almost nothing about where it has been during that time,” Crowe said in an email to USA TODAY. “We now know that this water flowed into the Bidahochi Basin (a geological depression in northeastern Arizona that once contained a large ancient lake) during this time and drained into what would become the Grand Canyon.”
What are the main takeaways from this study?
“Our study was motivated by an interest in testing the idea that a lake that feeds the Colorado River exists to the east of the Grand Canyon, and that overflows and overflows from that lake led to, or at least contributed to, the formation of the Grand Canyon,” Crowe said.
The results showed that from about 6.6 million years ago, the sand in the lake’s sediments began to show clear traces of the Colorado River, indicating that the river flowed into the lake.
How did the Grand Canyon begin?
Crowe said the findings show that the lake, which feeds into the Colorado River, must have played a major role in the formation of the Grand Canyon and the birth of the Colorado River system, likely pooling east of the Grand Canyon before draining and establishing its course in what would become the Grand Canyon.
About 2 million years later, the lake no longer existed, and the Colorado River system was fully formed and even integrated into the ocean, he added.
“Parts of the Grand Canyon may have been partially carved out by other river systems, but it was the Colorado River that connected them,” Crowe said.
The study also highlights that the Colorado River in 2026 will be very different from the body of water that formed the canyon.
“We increasingly understand that river systems are integrated by linking a series of closed basins through a descending process where each basin fills and then drains into the next basin,” Crowe said.
Doyle Rice is a national correspondent for USA TODAY, focusing on weather and climate.
