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California Was Formed by Geologic Immigrants

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DRAMATIC is an adjective people often use to describe California's scenery, and for good reason: It is.

Driving north along the coast, you see the grass- and oak-covered slopes of the coastal ranges rising up out of the Pacific Ocean. Going north inland from Los Angeles to Bakersfield, Interstate 5 reaches a final crest at Tejon Pass, a gap in the Tehachapi Mountains, and plunges into the Great Central Valley.

As the highway begins its descent, the mountains break to either side and run north as far as the eye can see, embracing the flat expanse of valley that stretches out ahead.

Driving along the twists and turns of the Angeles Crest Highway in the San Gabriel Mountains, you can glimpse eastern slopes of forest pine giving way to the buff-colored desert floor to the east. From that same vantage point and to the north, the Tehachapi Mountains rise from the desert and stretch northward until they meld with the snowcapped Sierras. The eastern slopes of the Sierras stand like granite ramparts above the floor of the Owens Valley.

These dramatic vistas reflect the impact - literally - of hundreds of millions of years of restless motion of the earth's crust, a history that, with the help of tectonicist Eldridge Moores, John McPhee sketches in his book "Assembling California."

"For an extremely large percentage of the history of the world," McPhee writes, "there was no California.... The continent ended far to the east, the continental shelf as well. Where California has come to be, there was only blue sea.... Then, a piece at a time - according to present theory - parts began to assemble. An island arc here, a piece of continent there - a Japan at a time, a New Zealand, a Madagascar - came crunching in upon the continent and have thus far adhered."

"Assembling California" completes a four-part series that began with McPhee's "Basin and Range" in 1980. Traveling west along Interstate 80, McPhee and his geologist-guides use roadcuts as windows into the geological history of North America. In this case, the guide is Dr. Moores of the University of California at Davis, one of the key figures in the development of the theory of plate tectonics.

Over a 15-year period, the two researchers traveled I-80 from Reno to San Francisco, examined similar geological formations in Cyprus and Macedonia, and in the process set the outlines of a story that unfolds in this book much as California did: in fascinating but distinct chunks.


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