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Earth Science

Humans Causing California's Mountains To Grow 36

New submitter Megan Sever writes: "This is a cool story about anthropogenic effects of water withdrawal moving mountains — literally. According to new research published today (abstract) and reported in EARTH Magazine, humans have been causing the Sierra Nevada mountains to rise. By withdrawing water for irrigation and other purposes, we have inadvertently removed water from the mountains, allowing them to uplift. The research shows a seasonal and annual cycle."
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Humans Causing California's Mountains To Grow

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  • by Required Snark ( 1702878 ) on Thursday May 15, 2014 @03:35AM (#47006861)
    Historically, the Salon Sea in inland Southern California has long term wet and dry periods. When it is filled with water there tend to be earthquakes in the region of the San Andreas Fault that run through the Salton Sea area. When it is dry there tends to be a much longer period between major quake in this part of the fault. []

    The Salton Sea and surrounding basin sits over the San Andreas Fault, San Jacinto Fault, Imperial Fault Zone, and a "stepover fault" shear zone system. Geologists have determined that previous flooding episodes from the Colorado River have been linked to earthquakes along the San Andreas Fault. Sonar and other instruments were used to map the Salton Sea's underwater faults during the study. During the period when the basin was filled by Lake Cahuilla, a much larger inland sea, earthquakes higher than magnitude 7 occurred roughly every 180 years, the last one occurring within decades of the year 1700. Computer models suggest the normal faults in the area are most vulnerable to deviatoric stress loading by filling in of water. Currently, a risk still exists for an earthquake of magnitude 7 or 8. Simulations also showed, in the Los Angeles area, shaking and thus damage would be more severe for a San Andreas earthquake that propagated along the fault from the south, rather than from the north. Such an earthquake also raises the risk for soil liquefaction in the Imperial Valley region.

    After the last flood from the Colorado River into the Salton Sea after 1900, a series of dams were built to keep the river from flowing into California. Since then there are been no really large magnitude earthquakes from the San Andreas in Southern California.

    It seems extremely likely that human activity has altered the earthquake pattern. This means it is possible that removing large amounts of ground water from the San Joaquin Valley could measurably effect the height of the Sierra Nevada mountains.

The first rule of intelligent tinkering is to save all the parts. -- Paul Erlich