The Green River doesn’t make a lot of sense at first glance. The Colorado River’s largest tributary flows through a nearly 2,300-foot-deep canyon inside of northeastern Utah’s Uinta mountain range. But at almost 2.5 miles high, the massive, 50-million-year-old rock formation hypothetically shouldn’t have even yielded to the nearby Green River, which itself began to form less than eight million years ago. … According to the coauthor of his team’s study published on February 2nd in the Journal of Geophysical Research: Earth Surface, the region is “enormously significant” to the overall landmass. “The merging of the Green and Colorado Rivers millions of years ago altered the continental divide of North America,” he [geologist Adam Smith] explained in a statement.