Assembling California

At various times in a span of fifteen years, John McPhee has made geological field trips in the company of Eldridge Moores, a tectonicist at the University of California at Davis. The result is Assembling California, a cross-section in human and geologic time, from Donner Pass in the Sierra Nevada through the golden foothills of the Mother Lode and across the Great Central Valley to the wine country of the Coast Ranges, the rock of San Francisco, and the San Andreas family of faults. The two disparate time scales occasionally intersect - in the gold disruptions of the nineteenth century no less than in the earthquakes of the twentieth - and always with relevance to a newly understood geologic history in which half a dozen large and separate pieces of country are seen to have drifted in from far and near to coalesce as California. McPhee and Moores also journeyed to remote mountains of Arizona (where Moores grew up in a gold-mining camp), and to Cyprus and northern Greece, where rock of the deep-ocean floor has been transported into continental settings, as it has in California. A specialist in such ocean rock and the histories it suggests, Moores routinely works at the applied outer boundary of the theory of plate tectonics, reconstructing ancestral worlds. Presented here in global dimension is a sweeping narrative of maps in motion, of evolving and dissolving lands. In 1978 and 1979, John McPhee also began his wider series of related journeys, traversing North America at about the fortieth parallel, using roadcuts of interstate 80 as windows into regional geologies, and incidentally profiling the lives of the geologists with whom he travelled. A continental tetralogy, gathering underthe title Annals of the Former World, began with Basin and Range (1980), and continued with In Suspect Terrain (1982) and Rising from the Plains (1986), and is now completed by Assembling California. In the overall structure of these compositions, the controlling element has been not a simple geographic itinerary but a set of thematic jumps from place to place in the light of the theory of plate tectonics, which, when the author began, was only ten years old.