Abstract
The study of the earth, its structure and history, is facilitated by those areas where mountain building or erosion has exposed the rocky framework of the earth. The Rocky Mountains of North America display a wide range of geology. In Colorado, the granite core is often exposed. Farther north, especially in the Yellowstone Region, volcanics have shaped the landscape. Breccia and conglomerate composed of basalt, andesite or other volcanic products can be seen. Still farther north (Glacier National Park, for instance), Precambrian sediments predominate.