Roadside Geology Of MontanaMontana's geologic history includes a long succession of disturbances that changed the rocks, then changed many of them again. Unraveling these events reveals a geologically quiet continent that got scrambled in a long and grinding collision with the Pacific crustal plate. Through detailed geologic maps and lively text, Roadside Geology of Montana deciphers the complicated rock record and uncovers each layer of Big Sky Country. David Alt and Donald W.