Geologists trace Colorado River’s ‘missing’ 5 million years to ancient lake spillover

A Science study used detrital zircon dating from the Bidahochi Basin to link its sediments to the Colorado River.

The results support the lake-spillover hypothesis: the river likely filled an ancient lake and then overflowed into the Grand Canyon about 6.6 million years ago.

That timeline helps settle a major geology debate over when the Colorado River connected to the canyon and when canyon carving began.