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Fault Line

January 26, 2006

San Francisco and Los Angeles are on different tectonic plates. One listener asked what consequences that has for the future of California.


A tectonic time machine. I’m Bob Hirshon and this is Science Update.

Los Angeles and San Francisco are creeping together as their tectonic plates slip past each other in opposite directions. Robert Briggs of Peterborough, England, asked how long it’ll be before the cities are next to each other.

Stanford geophysicist Mark Zoback did the math for us. San Francisico and Los Angeles are about 300 miles apart, and they move about 2 inches closer each year.

MARK ZOBACK (University of Stanford):
So at the rate at which the North American plate and the Pacific plate are moving past one another, it will take approximately 10 million years for Los Angeles to be across from San Francisco.

He says things could change before then, but chances are they’ll continue as they have for the past 10 million years. If you have a science question, call us at 1-800-why-isit. I’m Bob Hirshon, for AAAS, the science society.