About 70 million years ago, eastern Colorado was basically at sea level. Today, the region is about 6,500 feet higher, depending on where you are. Researchers at University of Colorado-Boulder have one explanation of how that could've happened:
It seems water trapped in the Earth's crust may have flooded the lower crust, lifting the land up.
In other words, “It’s like flooding Colorado from below,” said the researcher's lead author Craig Jones.
Jones had a lightbulb moment for the theory when colleagues noticed that pieces of crust from near the Canadian border were very rich in one mineral. But farther south, the pieces were more hydrated and had other less-dense minerals.
