A new scientific study sheds light on how and when the Colorado River began to form the Grand Canyon, one of the world’s most spectacular geological phenomena, answering a question that has plagued the scientific community for years.

Researchers analyzed tiny zircon grains found in sandstones – sediments carried by the river – as well as volcanic ash particles to trace their past pathways. Through this process, they were able to reconstruct how the river’s course evolved during a crucial period in the creation of the canyon. The study was published in the journal Science.

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According to the findings, about 6.6 million years ago, the Colorado River began flowing toward a large basin in northeastern Arizona, forming an extensive and shallow lake east of the current site of the Grand Canyon. This lake, which researchers unofficially call “Lake Bidahochi,” is estimated to have been more than 150 kilometers wide and was located in what is now part of the Navajo Nation.

Over time, the waters accumulated until, about 5.6 million years ago, they overflowed from a low point in the basin. This overflow was a pivotal moment, as water began to flow through the area, gradually opening up the route that evolved into the current canyon.

The river then passed through successive basins and finally, about 4.8 million years ago, ended up in the Gulf of California in northwestern Mexico.

The Grand Canyon, about 450 kilometres long, up to 29 kilometres wide, and more than 1.8 kilometres deep, is the product of millions of years of erosion. Its rocks are up to 1.8 billion years old, revealing the “architecture” of the Earth over time.

Scientists point out that the process has not stopped. The river continues to erode the rocks at a rate of about 100 to 160 meters per million years, gradually shaping the landscape.

As the researchers said, it was previously known that the river existed in western Colorado 11 million years ago and that it did not cross the Grand Canyon until 5.6 million years ago. However, what happened in the intervening time remained largely unknown.