Steamboat Rock sits near Echo Park, where the Green (bottom) and Yampa Rivers meet in Dinosaur National Monument, Colorado Plateau. The prominent white layer is the Weber Sandstone, of Pennsylvanian age. It and the older Morgan Formation below it are bent up by the Mitten Park Fault on the left, which brings up the Proterozoic Uinta Mountains Supergroup on the left. The Weber Sandstone was deposited as the Ancestral Rockies were being created, while the folding and faulting at left dates from the early Cenozoic when the modern Rockies were made. The structure here is part of the eastern end of the the major structure that threw up the Uinta Mountains farther west.