The uplift of the range dates to the Laramide orogeny, about 70 to 50 million years ago, when compressive forces produced high-angle reverse faults on both north and south sides of the present mountain range. The east-west orientation of the Uintas is anomalous compared to most of the ranges of the Rocky Mountains; it may relate to changing stress patterns and rotation of the Colorado Plateau.[6] The Green River used to flow into the Mississippi River to the Gulf of Mexico, but changed to the Colorado River by going through the Uintas in ways not fully understood.[7]