The first of John McPhee's works in his series on geology and geologists, is a book of journeys through ancient terrains, always in juxtaposition with travels in the modern world—a history of vanished landscapes, enhanced by the histories of people who bring them to light. The title refers to the physiographic province of the United States that reaches from eastern Utah to eastern California, a silent world of austere beauty, of hundreds of discrete high mountain ranges that are green with junipers and often white with snow. The terrain becomes the setting for a lyrical evocation of the science of geology, with important digressions into the plate-tectonics revolution and the history of the geologic time scale.