Journalist Brown (Newsweek, Discover, etc.) spent two years trekking the Pacific coast from Baja California to the Aleutian Islands to profile the geology of the region. Here, a cast of US Geological Survey and other government scientists, as well as oil men, academics, local citizens, historians, and anthropologists, enrich the author's already well-informed background to produce a richly detailed, up-to-date account of what happens when Pacific and North American plates meet. Some of what happens is well-known: earthquakes and tremors...vulcanism and mountain-building...fear and trembling along the San Andreas fault. But a lot isn't: The west coast of North America is one of the most complex and dynamic terrains anywhere--the Pacific Plate is moving north at a rate of six inches a year, so that eventually L.A. and San Francisco will nestle in the Arctic, where a new continent is forming. Meanwhile, plate- spreading along the East Pacific Rise (the boundary between the Pacific and North American plates) is creating an ocean between Baja California and mainland Mexico. Brown's journey started in Baja, with stops in L.A., Monterey, San Francisco, and points north, through Oregon, Western Canada, Alaska, and, finally, the Aleutians. While the bulk of his narrative is taken up with theory and explanation--why there's so much oil under L.A.; what caused the 1989 San Francisco quake (and why there's a 50 percent chance of another big one in the next 30 years)--there's also fine detail of flora and fauna, descriptions of shady characters like the early oil men, and a poignant history of the Aleuts. Regrettably, in a text that cries out for photos and illustrations, there are none. Instead, we get good science writing, in a style less didactic and assertive than McPhee and more in the spirit of the ``amateur''--the lover of the subject who wants to tell you all about it.