The Pacific and mountain states include Montana, Wyoming, Idaho, Washington, and Oregon. While the geology in these states has been mapped and their geologic units described, their geologic evolution and history is still being refined. Northwest Exposures: A Geologic Story of the Northwest by David Alt and Donald Hyndman is a generalized description of the entire region’s geology. Geologic Atlas of the Rocky Mountain Region, United States of America, edited by William Mallory et al., synthesizes what was known about the region’s geology at the time of publication. The atlas includes information on the regional geography, geology, and geophysics; an extensive series of historical geology chapters containing rock descriptions, cross-sections, and maps for geological eons and periods; and a section on the economic geology of the region. In Cascadia: The Geologic Evolution of the Pacific Northwest, Bates McKee summarized the geologic record of the western part of this region, but acknowledged that ideas about the region’s geologic evolution will change as knowledge about plate tectonics increases. Unfortunately, McKee died before he could write another edition. William Orr and Elizabeth Orr provide a more current summary of the geology of the region west of central Idaho in Geology of the Pacific Northwest.
Geologic Resources of Montana: 1989 Field Conference Guidebook, edited by Don French and Robert Grabb, is a collection of technical papers on the exploration, stratigraphy, paleontology, structure, and natural resources of Montana, although it is not a comprehensive summary of the state’s geology. Eugene Perry’s Montana in the Geologic Past contains descriptions of Montana’s sedimentary and igneous rocks, glaciation, fossils, and mineral resources. The Montana Bureau of Mines and Geology, Montana Geological Society, and U.S. Geological Survey have published many reports, guidebooks, and symposium volumes on the geology of various areas and resources of Montana. Given the size of the state and its complex geology, people looking for information on Montana geology may have to consult individual volumes on specific areas.
The geology of Wyoming has been described in two different publications. Geology of Wyoming, edited by Sheila Roberts, James Steidtmann, and Arthur Snoke, is a collection of technical articles on topics related to Wyoming geology, geologic history, structure, and natural resources. It includes articles describing Wyoming during various divisions of geologic time, the geologic structure of the state, and geologic and energy resources. Donald Blackstone’s Traveler’s Guide to the Geology of Wyoming describes the state’s geology in more general terms. In addition, the Wyoming Geological Association has published many guidebooks on the geology of various areas; these include summary articles and road logs to significant geological sites.
Exploring Idaho Geology by Terry Maley is a general summary containing information on the rock types, physiography, geologic structure, paleontology, mineral resources, and significant geologic sites in Idaho. Three field trip guidebooks, Guidebook to the Geology of Central and Southern Idaho, edited by P. Link and William Hackett, Guidebook to the Geology of Northern and Western Idaho and Surrounding Area, edited by V. Chamberlain, Roy Breckenridge, and Bill Bonnichsen, and Guidebook to the Geology of Eastern Idaho, edited by Scott Hughes and Glenn Thackray, provide more technical geologic descriptions of each region of the state in summary articles. They also include road logs to important geologic sites in each region.
Northwest Origins: An Introduction to the Geologic History of Washington State, a website created by Catherine Townsend and John Figge for the University of Washington’s Burke Museum of Natural History and Culture, documents the geologic history of the state in general terms. The site also includes an extensive reference list to other general and technical publications on the state’s geology. Evolution of the Pacific Northwest: An Introduction to the Historical Geology of Washington State and Southern British Columbia by John Figge is a 355-page book that describes the geologic history and evolution of Washington as a series of episodes in which new land was added to the Pacific Northwest. The book (never published in print) is available free online.
Oregon Geology by Elizabeth Orr and William Orr provides a comprehensive description of the geology of the state, including information on geologic hazards and natural resources and an extensive bibliography. Ellen Bishop’s In Search of Ancient Oregon: A Geological and Natural History traces the state’s geology and life forms from its earliest rocks to the present in more general terms.