Geologic Map of California
(c) 2003 Andrew Alden, licensed to About.com, Inc. (fair use policy)
This is the postcard-size version of U.S. Geological Survey Map I-512, published in 1966. Our ideas of geology have come a long way since then, but the rocks are still the same.
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 a lifetime's worth of geological attractions.
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 California Geological Survey has a PDF of the map at roughly this scale, weighing 866 KB.
The jumbo version is 3122x4137 pixels (3 MB). It ought to print real nice if you have a large-scale printer.
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