Geologists have discovered that the Colorado River has not taken its route from the Rocky Mountains down into western Colorado for nearly five million years, indicating a significant gap in time. A sediment analysis suggests that the river once pooled up into a natural reservoir just east of the Grand Canyon. Geologists from Paradise Valley Community College in Arizona, the U.S. Geological Survey, and several universities across the American West, led the researchers to rigorously test their findings against fossils and geological records. The researchers believe that the water once flooded into the Bidahochi basin on Navajo Nation land before spilling over the top of the Colorado Plateau into the old gorges that would become the Colorado Canyon. The study's lead author, John Douglass, credits the discovery to microscopic crystals called zircons, which can act like a tracer as they are washed downstream from the shifting flows of the river.