Assembling California is the final book in John McPhee’s geological tetralogy, Annals of the Former World. “Assembling” refers coyly to the two-decade-old theory of plate tectonics, which the three preceding books (Basin and Range, 1980; In Suspect Terrain, 1982; and Rising from the Plains, 1986) explained for those readers who survived the exposure to thick geological nomenclature. Tectonic geologists have embraced McPhee as one of their own, given his immersion in the topic and skill at discussing it. He dedicates Assembling California to Kenneth Deffeyes, the geologist who accompanied him to the Western states to look at road cuts, the freeway builder’s gift to students of rocks. But when McPhee entered California near Tahoe with the ever-prescient Deffeyes, the geologist was stumped by rock he did not recognize, and referred the author to his California alter ego, Eldridge Moores. Assembling California is the fruit of trips with Moores over several years during the 1980’s.
Geology is not humanities or anthropology, as the time charts on the book’s endpapers make clear. The most recent geological era is the Cenozoic, which traces time back a mere 65 million years. The three preceding eras begin with Precambrian time, which originates in the Hadean Eon, dated at 4,600 million years before the present. In that four-era-long wealth of time, plate tectonicists assert, the earth has been in a constant state of topographical rearrangement, such that supercontinents have more than once formed, broken apart, and re-formed. McPhee imparts this perspective with as much expertise as a lover of the subject can develop, professionals included. The earth, he writes, is “a planetary shell so mobile that nothing on it resembles itself as it was some years before, when nothing on it resembled itself as it was some years before that.” Geology addresses infinity, the persistent replacement of land with oceans and vice versa, and the continuance of all this in the present at the same, to human senses, immeasurably slow pace. McPhee’s explication of this phenomenon, parts of it admittedly hypothetical, is as close to an act of worship as a three-hundred-page book can come without ever invoking the name of God.
The art of John McPhee has always been to wrest marvels from the mundane. He can write about whiskey, oranges, canoe building, tires, Alaska, roadkill, Atlantic City, or Bill Bradley, and the reader is hard-pressed to decide if it is the subject that fascinates or McPhee’s energized consciousness of it. He brings a poet’s sensibility to the most tangible things. Writing about geology, this feaster on the detail beneath the detail asks readers to follow him into a subject as complex as a medical subspecialty with the accompanying technical lingo. Because McPhee is writing, the reader most likely will comply.
In Assembling California, McPhee’s strategy remains what it has been in many of his books: He stage-manages the presence of a man or woman who knows the subject. The world is not facts, he tacitly proposes, but personalities generating ideas, attitudes, products, and lives. To know California’s geology, one gets to know Eldridge Moores, a geologist who works out of the University of California, Davis. McPhee is interested in presenting geology as a subject while showing how the subject comes into being. Plate tectonics is a new vision. It exists as the community of geologists senses it, defines it, modifies it, fights it, and believes it. The work of human thought and perception, making discoveries and diving deep into time through stone, is as major a drama for McPhee as the earthquakes—past, present, and future—which are the most dramatic effects of tectonic action. If the world is assembling and disassembling itself as tectonics proposes, so is the scientist’s evolving vision. Geologists relish the uncertainty. McPhee quotes a volcanologist in this regard: “In the next ten years, our confusion will reach new heights of sophistication.”
Much of Assembling California recounts trips McPhee took with Moores into California’s Sierra Nevada Mountains, where the evidence of tectonics can be most easily read. In this high range, sloped gradually to the west, dropped abruptly from its summits to the basin floor to the east, Moores demonstrates through the visible rock the subduction which caused the range to form. In “subduction,” a central concept for plate geology, one plate pushes under another as the two plates meet. A shape like the Sierra Nevada is formed, much like the effects on a car fender in a collision, a collision which consume centuries and blends rock and leaves debris at a messy joint and at new elevations. As McPhee noted in Basin and Range, and repeats here, “The summit of Mount Everest is marine limestone.” Whether the geologist looks at the Sierras, the Alps, or the Himalayas, he is reading the junction of plate contact.
A vintage McPhee analogy gives the reader some sense of what the geologist is seeing at such a “suture.” Imagine an attic that houses pieces of furniture differing widely in date and style:
You also see, lined up in close ranks, a...