Source of book: I own this.
I first discovered John McPhee a half decade ago when my wife’s brother-in-law got me what was then his latest collection, The Patch. At that time, I must have read an essay of his somewhere or other, but wasn’t that familiar with him.
Soon afterward, though, I learned that a lot of his writing was about geology. My next book of his was Basin and Range, which is one of his five books - including Assembling California - about the geology of North America, that he subsequently combined into a set under the name Annals of the Former World. Which is a badass title, I must say.
Coincidentally (or not?), my eldest decided to major in Geology, thus becoming even more of a rock nerd than I am. Who knew? This meant I got him a copy of Assembling California, but hadn’t yet read it myself. Well, now I have, and greatly enjoyed it.
This book follows a somewhat similar format to the other, but with some differences. In Basin and Range, McPhee and his friend, Geologist Kenneth Deffeyes, travel Interstate 80 through the Great Basin, and McPhee talks about what they see before explaining how it got there and when. The personal and the geologic scales come together.
Assembling California picks up exactly where Basin and Range left off: at the California and Nevada border.
However, as Deffeyes tells McPhee in the first chapter, to complete the journey, McPhee will need to find a new geologist: one with knowledge and expertise in the muddle that is California.
Enter Eldridge Moores.
McPhee and Moores travel Interstate 80 from Reno to San Francisco, with a side trip to Moores’ childhood home in the Arizona mining country, an excursion to Cypress, and a longer exploration of the San Andreas fault in the final chapters of the book.
As with the other book, this one is really a lot of fun. McPhee knows how to provide incredible detail and scientific content without overwhelming, and paces the stories and information in a way that it never gets dull.
And wow, what a story this book really is.
There are places in the world where geological history is relatively simple and easy to understand. As any Californian who gets out in the wilderness and looks at rocks can tell you, California is a big complicated, nearly incomprehensible muddle.
It wasn’t until plate tectonics was understood that any sense could be made of California. Sure, the great plutons of the Sierra Nevada are relatively simple. And there are some places of normal sedimentation.
But the layers mostly don’t work. Particularly in the west of the state, everything looks much more like sausage or chunky ice cream - it’s mixed up and ground together and random.
I won’t be able to do it justice, but here is the basic natural history of the place:
Once upon a time, the edge of what is now the Rocky Mountains was the western edge of what would become North America. After the breakup of Pangaea, plate tectonics smashed the edge of the Pacific Plate into the North American Plate.
But it didn’t just come with a subduction zone. Rather, in some cases the ocean plate overrode the continent, leaving vast layers from mantle rock through serpentine to pillow basalts and ocean sediments.
Add to that the island belts that collided with the continent and added on to it, and you have quite the Dagwood Sandwich of geologies.
Very late in geologic time, the subduction shifted to a slip-strike - aka transform - boundary, creating the San Andreas Fault, stretching the great basin into tilted blocks that formed the Basin and Range system and even Death Valley itself.
There is so much more to this than I have condensed into a few paragraphs - and it really is a fascinating read.
If you wanted to know how gold and silver made it to California, this book will tell you. If you, like me, are a Californian who loves to explore, this book will explain so many of the natural wonders you have loved since childhood.
I also want to take a road trip to look at rocks now - preferably with my future geologist kid.
As usual, there are so many great lines in this book. McPhee is quite witty, as are his geology buddies. It is a dry sense of humor - or perhaps as gritty as the rocks that make up the book.
Here is one to start with, a gem from Moores:
“If you want to find a fault in California, look for a dam.”
This may seem like gallows humor, particularly given the way faults have often caused dam failures. But it is also accurate. The best place for a dam is a narrow crack through a mountain range, right? Well, what causes those? Faults. That’s where the river is able to grind its way through.
Probably the funniest line in the book comes in the chapter on the excursion to Cypress, where mining has been going on for over 5000 years. (Enough wood has been burned in smelting over that time to cover the island several times over with trees.)
The highest peak was Mt. Olympus. In the Hellenic world are enough Mt. Olympuses to suggest tract housing for redundant gods.
Although this one, about a side trip to Napa, is pretty funny too.
The Napa Valley is thirty-five miles due west of Davis - an easy run for a field trip, a third of it flat and straight. The occasions have been several, not to mention spontaneous, when Moores and I have made westering traverses, collecting roadside samples of rock and wine.
This quip, about the sausage of a common formation in the muddled western side of California, is pretty good too. And accurate as well as descriptive.
If the Great Valley Sequence can be compared to regimental stripes, the Franciscan is paisley.
And what is this formation?
The Franciscan melange contains rock of such widespread provenance that it is quite literally a collection from the entire Pacific basin, or even half of the surface of the planet. As fossils and paleomagnetism indicate, there are sediments from continents (sandstones and so forth) and rocks from scattered marine sources (cherts, graywackes, serpentines, gabbros, pillow lavas, and other volcanics) assembled at random in the matrix clay. Caught between the plates in the subduction, many of these things were taken down sixty-five thousand to a hundred thousand feet and spit back up as blue schist. This dense, heavy blue-gray rock, characteristic of subduction zones wherever found, is raspberried with garnets.
Although California is the focus of the book, getting into the broader plate tectonics often leads to other places, and how they fit in history. For example, the fact that the Appalachians are continued in the mountains of North Africa, Spain, and France. And Florida is a piece that broke off of Africa.
As part of a discussion of these historical events, Moores opines that “Civilization reflects geology.” I do wonder about that. It might be true. Just as one personal example, while I currently live on the North American Plate, I was born and raised on the Pacific Plate. Could some of this be a factor in why the big cities of California are politically different from the inland areas?
Here is another crazy fact:
While India was closing with Tibet, it buckled the intervening shelf, raising from the sea a slab of rock more than a mile thick which consisted almost entirely of the disintegrated shells of marine creatures. From the depths of lithification to the rock’s present loft, it has been driven upward at least fifty thousand feet. This one fact - as I noted some years ago - is a treatise in itself on the movements of the surface of the earth. If by some flat I had to restrict all this writing to one sentence, this is still the one I would choose: The summit of Mt. Everest is marine limestone.
It is things like this that made it impossible for me to believe in a young earth, or in a literal creation story. It just doesn’t fit.
That isn’t to say that at any one moment we know the full truth. In fact, plate tectonics is barely 70 years old - Moores and McPhee learned the old theories and had to switch as educated adults. But, as the book examines in detail throughout, the old theories were known to be flawed and incomplete. Tectonics illuminated so much that was obscure. But we will likely understand more over time.
There is a great quote (maybe) by Mark Twain in the book that I can’t resist mentioning.
“Researchers have already cast much darkness on the subject, and if they continue their investigations we shall soon know nothing about it at all.”
As I mentioned, the San Andreas Fault is the subject of the last quarter of the book. This makes sense, as the fault and the earthquakes we experience here are part of our unique geology.
I personally have experienced a number of earthquakes over my lifetime. The two strongest (from where I was at the time) were the Whittier Narrows quake (discussed briefly in the book) and the Northridge quake (which is not.) The most significant quake I felt, however, was the Loma Prieta quake of 1989. It was strong enough to be mildly felt where I lived in Los Angeles. In fact, we didn’t think much of it until the report a few minutes later that it was a major earthquake up north.
Interestingly, McPhee was in the Bay Area the day before the quake, but traveled up to Oregon before the quake hit. The book hints at his simultaneous disappointment and relief.
One interesting fact in this section is that the two reservoirs near San Francisco - the San Andreas and Crystal Springs - were built in the late 1800s. The dams survived the 1906 quake and the Loma Prieta quake (and numerous smaller quakes) intact, despite the fact that the fault runs right up the reservoirs.
I’ll also note the mention of Pinnacles National Park in the book - a favorite place of mine, and one I have written about multiple times.
Also mentioned is the Tejon Pass. During my teens and early 20s, I lived in the mountains a few hundred feet from the San Andreas - it created the series of valleys that towns up there are located in - and indeed built the mountains themselves. The pass is where Interstate 5 goes over the summit, and the faulting is obvious. You can literally see the different kinds of rock on the sides of the fault from the vegetation and erosion patterns.
Anyway, there was a huge earthquake there in 1857, and the sides of the fault were offset by thirty feet. This is an absolutely astonishing amount of movement. The quake must have been some violent shaking.
There is a similar offset still visible at Point Reyes, from the 1906 San Francisco quake. It’s worth visiting.
I mentioned the Whittier Narrows quake, which was the first earthquake I remember. It didn’t cause any serious damage to our house, but it did send some plaster down, broke some dishes, and violently threw me out of bed. As McPhee notes, the fault was previously unknown, but its discovery led to better understanding of the various deep blocks thrust to create anticlines as part of the greater fault zone where the plates meet. The San Andreas is the big one, but the stresses stretch for hundreds of miles on either side.
Well, those are my thoughts. There is so much more in the book, including first-hand accounts from the Loma Prieta quake. It’s definitely worth a read. While it is technically the last book in the series, all of them stand alone. You do not need to read them in order. All are worth checking out.
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