Scientists decipher the geological history of the Grand Canyon

Must ReadScience & TechnologyScientists decipher the geological history of the Grand CanyonBy Reuters -Apr 19, 2026The Grand Canyon is a marvel on the landscape of North America, a breathtaking geological feature in the southwestern U.S. state of Arizona presenting dramatic contours and richly colored vistas. Research is now providing insight into how and when the Colorado River, whose continuous might has carved out the canyon over millions of years, came to flow ​through the region. By studying tiny grains of the mineral zircon in sandstone made up of sediments carried by the river and particles of ash ‌from volcanic eruptions long ago, the researchers managed to trace paths that the river took in the past. The study indicated that the river, around 6.6 million years ago, began to flow into a large depression in the Earth’s surface, called a basin, in northeastern Arizona, forming a wide and shallow lake east of where the Grand Canyon later took shape. The lake water built up over time and eventually spilled over ​a low point on the lakeshore starting around 5.6 million years ago, sending it coursing through the region that became the Grand Canyon, the researchers found. The river ​then filled and spilled through another series of basins downstream from the Grand Canyon, ultimately reaching the Gulf of California about 4.8 million ⁠years ago, emptying into the sea at a spot in northwestern Mexico, they found. The lake, which may have reached a width of more than 90 miles (150 km), has long ​since disappeared. The researchers have informally called it Bidahochi Lake based on the name of a local geological formation. It was situated largely on what is now the Navajo Nation reservation. “Scientists ​have long debated when the Grand Canyon was carved, and our study contributes to that conversation,” said UCLA geologist John He, co-lead author of the study published this week in the journal Science. “Imagine you go out to a river bank and scoop up a handful of sand...