The Other California: Now this is a postcard for a Geologist!

In the run-up to a series of blogs on some less-than-familiar parts of my home state of California, I used some postcards that are available in just about any store or tourist trap in the state. They show the famous landmarks of the state, which usually happen to be very geological in nature, such as Yosemite National Park. Today's postcard, which I doubt would be found in the usual tourist haunts, is very useful in searching out the kinds of places I want to talk about in coming weeks. It is a geologic map of the state, a representation of California from a geologist's point of view. The colors on the map represent the types and ages of the rocks found around the state. This map really was on a postcard provided by the state geologic survey, and can be hard to read, so I have provided a larger format for seeing the information below (just click on the image for the bigger picture). This map was compiled in 1966, before the advent of plate tectonics theory, but it shows the rocks pretty well (the rocks didn't change; our interpretations of how they got there did). A more modern version of the state's geology can be found here as a pdf file.

People who see these maps for the first time may be intimidated by the sheer variety of rocks in our state. We have literally every kind of rock there is in abundance; volcanic and plutonic igneous rocks, sedimentary and metamorphic rocks, and an abundance of loose sediment (the yellow stuff, especially in the Central Valley and desert areas). A resident looking at the map to see where their house sits in relation to the famous San Andreas fault may dismayed to find that there are a great many faults in the state that they were not aware of!
To make some initial sense out of the geological chaos that is our state, the geologists noted areas in the state that seemed to share a common geological history, even if the rocks themselves are complex and highly variable. Note, for instance that most of the Sierra Nevada mountains are composed of granite (red), and that the Central Valley is mostly loose sediment. The northeast corner of the state is primarily volcanic in nature. These areas that have a unique geologic history that is distinct from surrounding areas are called the physiographic provinces of the state. The map shown below, from the U.S. Geological Survey, shows the boundaries of the eleven provinces of California superimposed over a geologic map (minus most of the faults, rivers and other features). As I start my journey to the unknown corners of the state, I will refer to their location in relation to the province in which they are found. The first entry in the series, on the California prairies, made reference to three such provinces: the Great Valley, the Sierra Nevada, and the Coast Ranges. More details on each of these provinces will soon follow!

The Other California: The things it is not

I wrote a post a few days ago about the "Other California", describing a section of the prairies that surround California's Central Valley, a much diminished and much ignored part of an extraordinary state. The title I gave the post stuck with me as I drove across about half the state on my way to a family Thanksgiving celebration, and I had the germ of an idea of a future series on Geotripper, a geologic tour of the parts of the state that most people never see. It occurred to me that if I am going to write about the "Other California", I need to define what the "Other California" is not, hence today's odd title.

It didn't take long to figure out how to find the places "everyone knows": I was on the road, there was a tourist trap with bathrooms, and a bunch of postcards for sale. What better place could there be for the attention-deficit-disorder tourist to find out the important sights to see. I grabbed two postcards showing the whole state (50 cents apiece or 3 for a dollar; I grabbed a third card that shows the famous Tehachapi Loop). The cards are published by Scope Enterprises, Inc (no web presence that I could find).

The first card has a lot of information packed in a small space: LA, San Francisco, San Diego, Disneyland, Napa-Sonoma, and much to my surprise, a whole gamut of Central Valley cities: Sacramento, my own Modesto, Stockton, Fresno, Visalia and Bakersfield. The national parks are there: Yosemite, Sequoia/Kings Canyon, Lassen Volcanic, Redwoods, Death Valley, Joshua Tree, and Channel Islands. Mentions of the coast, Hollywood, Salton Sea. All in all a pretty good effort at nailing down the main tourist destinations, pretty much a checklist for the first-time California traveler. It even includes a few of our state symbols, the Golden Poppy, the California Quail, and the state flag.

I like the second card even more: the Natural Wonders of the State. The same national parks, plus Lake Tahoe, the Colorado River (so big and wide that it looks like California is probably already falling into the sea), the Mojave Desert, Bristlecone Pines, California Condors, Sea Otters, Mt. Shasta, and Morro Rock. Best of all, a red dotted line representing the San Andreas fault winds its crooked way across the state. I don't necessarily expect perfection in postcard maps, but this one takes the cake!

So, in future posts about the "other" California, these are generally the places I won't be talking about (I may make an exception over Morro Rock and perhaps the Bristlecone Pines).