Assembling California by John McPhee
My rating: 5 of 5 stars
“The two time scales—the one human and emotional, the other geologic—are so disparate. But a sense of geologic time is the most important thing to get across to the non-geologist: the slow rate of geologic processes—centimetres per year—with huge effects if continued for enough years. A million years is a small number on the geologic time scale, while human experience is truly fleeting—all human experience, from its beginning, not just one lifetime. Only occasionally do the two time scales coincide.”
I absolutely love how well John McPhee does the intersection of human and geologic time scales in his Annals of the Former World geology books, making them about creation of continents how we know them while managing to bring people, despite their incredibly short timespans, into focus as well. McPhee is really great that way, and all of his books I’ve read so far are both wonderfully informative and just simply wonderful.
California, as McPhee tells us, was assembled as a result of collisions of a bunch of migrating islands coming up from the ocean floor, and of course now is shaking at the seams between them — those seismic faults on top of which we unknowingly built homes and businesses and university football stadiums. His description of Loma Prieta 1989 earthquake is enough to start doubting the good judgment of anyone living in earthquake country — but when has it ever stopped any of us?
“Where California has come to be, there was only blue sea reaching down some miles to ocean-crustal rock, which was moving, as it does, into subduction zones to be consumed. Ocean floors with an aggregate area many times the size of the present Pacific were made at spreading centers, moved around the curve of the earth, and melted in trenches before there ever was so much as a kilogram of California. Then, a piece at a time—according to present theory—parts began to assemble. An island arc here, a piece of a continent there—a Japan at a time, a New Zealand, a Madagascar—came crunching in upon the continent and have thus far adhered. Baja is about to detach. A great deal more may go with it. Some parts of California arrived head on, and others came sliding in on transform faults, in the manner of that Sierra granite west of the San Andreas.”
McPhee, as usual, travels through his chosen geographic area in a company of an actual geologist — the time it’s Eldridge Moores from University of California Davis. Together they traverse California from the Sierra Nevada to the Central Valley and follow the San Andreas fault through the San Francisco Bay Area, with the narration frequently taking a detour to the other parts of the world – India, Australia, the other parts of the US, etc. Earthquake stories and Gold Rush chronicles alternating with geology and plate tectonics made for a fascinating although a bit meandering mix, with McPhee’s descriptions being vivid enough to stick into my memory better than the visuals ever could.
Oh, and ophiolites. That’s the word of the month for me. Thanks, McPhee! My geological vocabulary has been notably expanded.
5 stars.
books are life 