Assembling California is the fourth volume of McPhee’s massive book about the geologic structure of the country. It dwells mostly on how the ideas of plate tectonics by themselves do not explain the geology of California.
As explained in my reviews of the previous volumes, McPhee spent years traveling along I-80 in the company of different geologists with the aim of describing the geologic formation of the country. In this volume, McPhee continues his travels along I-80, this time with geologist Eldridge Moores. They begin a series of journeys at the eastern border of California near Donner Pass, crossing to the Oakland/San Francisco area.
McPhee introduces the concept of the ophiolitic sequence, a sequence of rock strata that has been found to originate from ocean floor crusts. These crusts were ripped from the floor and mashed upward when an island arc, like that of Japan, collided with the western coast of the continent. Thus the ophiolites, which are the oldest rock, end up on top of mountains. The theory is that three such island arcs joined with the continent over the ages to form California.
McPhee also travels with Moores to Cyprus and Macedonia, two areas with similar rock. He introduces some other structures that are not completely explained by plate tectonics, such as the whole of Southeast Asia, which appears to be a part of the continent that was pushed sideways by the impact of India smashing into Asia and creating the Himalayas.
McPhee finishes this book with a dissection of the 1989 earthquake in San Francisco-Oakland (which occurred after his initial visits). He returns to examine the damage and explain how the shockwave spread and why some areas were more damaged than others.
As in the other volumes, McPhee imparts a great many concepts and theories in clear and interesting prose. This series of books (or the larger volume) makes for reading that can be a little difficult to grasp, as plates and continents seem to whirl and gyrate all over the earth (only, of course, very slowly), but it is nonetheless fascinating.