The area of Badlands known as the Blues lies about fifteen miles east of Tropic on Highway 12. In this area, Tropic shale has weathered into barren hills and intricate drainage patterns. The shale was deposited about eighty million years ago during the Cretaceous period, when Utah was covered by a large ocean. As a result, Tropic shale is a good place to look for marine fossils, particularly oysters and mollusks.
This shale is seen farther to the northwest around the base of the Henry Mountains and near Cainsville where it goes by the name of Mancos shale. Different names, but it is essentially the same rock deposited in the same environment. One of the best options for exploring the Blues is to drive the jeep trail up Henderson Creek. This trail is accessed from the town of Tropic.