Earthsky asks: Why haven’t earthquakes toppled these balancing rocks?







Earthsky asks a very good question.  It looks as if someone (not me!) could climb up there and give that top rock a good shove and that would be that.   However, the article describes these rocks, located near Searchlight, Nevada as being near the San Andreas Fault and the San Jacinto Fault.

“Near” is a relative term.  In Southern California, the San Andreas Fault located north of the San Gabriel mountains in L.A. County, through the Cajon Pass and south of the San Bernardino mountains in San Bernardino County and runs south through Riverside County west of the Salton Sea and then south from there.  The San Jacinto fault runs further west.  That is a good afternoon drive from Searchlight, Nevada.


But, the seismologist Lisa Grant from UC Irvine who studied this phenomena found precarious rock formations almost right on top of the two faults. Those are shown in the picture on the right.   How could that be?

The published study in the Seismological Research Letters suggests that the interaction between the two faults has weakened the ground shaking from earthquakes on the ground near them.

I think that’s more than plausible, although I stress that I’m not a seismologist.  I’ve lived (off and on) in California now 61 years this month.  I’ve been hearing about “the big one” almost the whole time.  While we have had serious earthquakes that did tremendous damage, we keep hearing, “That’s not the big one, yet.” Perhaps like a “dormant” volcano, the San Andreas has become a dormant fault.  Of course, geologists say there is no such thing as a dormant volcano.   Maybe we don’t know what we don’t know.  For the full article check the above link at Earthsky.

Thanks to Earthsky

Photo Credits:  Nick Hinze, Nevada Bureau of Mines & Geology

                            Lisa Grant Ludwig, University of California, Irvine


About Richard Rollo

I am a retired Community College Instructor. I taught Political Science 1 American Government for 22 years in Southern California. I am originally from Northern Minnesota. My earliest years were spent in the living quarters of a rural Duluth Winnipeg & Pacific Railway Depot. Then my family joined the great 1950's migration to Southern California where I joined up with fellow baby boomers in overcrowded schools.
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