An informative guide to the geology of the Colorado Plateau, some of the most ruggedly beautiful land in the southwest. The book, an oversized paperback, is organized geographically by park or monument, including several pages each on Arches, Canyonlands, Chaco, Grand Canyon, Mesa Verde, Zion and other natural areas. With mostly black-and-white photographs, maps, diagrams and glossary.  (USW380, $16.95)