How the Grand Canyon formed is a surprisingly messy story. Here's the latest clue

A new study provides evidence for how the Grand Canyon formed by analyzing sand deposits that show an ancestral Colorado River filled Arizona's Bidahochi basin around 6.6 million years ago, creating an enormous lake that eventually spilled over into what became the Grand Canyon. Researchers matched pink, rounded sand grains from both locations using zircon crystal dating, confirming they originated from the same Colorado River watershed. This spillover hypothesis explains a crucial five-million-year gap in the river's timeline and suggests the lake overflow established the canyon's modern path, though some geologists remain skeptical about whether the lake was large enough to be the primary catalyst.