Between the red swath signifying the Sierra Nevada granites and the western greenish-yellow band of folded and faulted Coast Ranges lies the great sedimentary trough of the Central Valley. Elsewhere this simplicity is broken: in the north, the blue-and-red Klamath Mountains are torn from the Sierra and moved westward while the dotted pink is where young, widespread lavas of the Cascade Range bury all older rocks. In the south, the crust is fractured on all scales as the continent is being actively reassembled; deep-seated granites marked by red, rising as their cover erodes away, are surrounded by vast aprons of recent sediment in the deserts and rangelands from the Sierra to the Mexican border. Large islands off the southern coast rise from sunken crustal fragments, part of the same vigorous tectonic setting.
Volcanoes, many of them recently active, dot California from the northeast corner down the eastern side of the Sierra to its southern end. Earthquakes affect the whole state, but especially in the faulted zone along the coast, and south and east of the Sierra. Mineral resources of every kind occur in California, as well as geological attractions.
I have created versions of this map that include the explanation and key to the different rock units. The 1000x1300 version weighs 750 KB. The Explanation is readable, as are all but the smallest map labels.
The 1250x1600 version weighs 1 MB. All the text is readable, but there is some slight image degradation from the compression.
The jumbo version is 3122x4137 pixels (3 MB). It ought to print real nice if you have a large-scale printer.
More California resources on About.com:
About Los Angeles
About San Diego
About San Francisco
About Santa Rosa
California Geography, State Symbols & Facts
Los Angeles Travel
San Francisco Travel
California National Parks
California State Parks