|
||
The Shaky Future of the Salton SeaA former desert oasis faces environmental challenges, a water crisis and someday the Big One. Why we can't let the sun go down on the Salton Sea.By Robert Monroe For a glimpse into California's water future, consider the fate of a water destination from yesteryear. Many of the hamlets that surround the Salton Sea, a lake two hours east of San Diego, are mostly ghost towns. The resorts that made it a rival to Lake Tahoe in the 1950s have been replaced by junkyards and rusted signs with words like "pool" and "vacancy" on them. Caught in the tug-of-war between metropolitan and agricultural demands for water, the sea itself is shrinking as evaporation is outpacing runoff. As a consequence, the salinity of the sea is increasing and that's only part of the problem. Chemicals from agricultural runoff are also turning it into a concentrated broth. The new dynamic has caused the ecosystem in the Salton Sea to shift. Algae blooms diminish oxygen concentrations in the water. Hardy tilapia are the last fish to survive here, but just barely. During hot summer months, gypsum crystals clog their gills and cause fish kills in the millions. Such large die-offs have prompted the state of California to hire people to skim dead fish off the surface. The only movers and shakers left in this shrinking desert pool are hidden beneath it. Across the bottom of the lake are scars and cracks caused by the motion between two major faults -- the San Andreas and San Jacinto. This motion accommodates 40 millimeters (1.6 inches) of slip between the Pacific and North American plates every year, making this region, known as the Salton Trough, one of the most tectonically active places in North America.  
Such activity will manifest itself someday as the Big One, a spasm that will relieve stress on the San Andreas at the expense of some portion of Southern California. In fact, information being uncovered by scientists at Scripps Institution of Oceanography at UC San Diego suggests that this region of the San Andreas Fault system has a high probability for the Big One sooner rather than later. Earthquakes have recurred at the sea roughly every 200 years for the last thousand years, but it's been 335 years since the last quake. Scripps geophysicist Graham Kent won't say that the area is "overdue" for a seismic event. That would imply a certainty about earthquake behavior that scientists just don't have. "Imagine you're 9 months pregnant," Kent said by way of alternate explanation. "You're somehow coming to the end of a process." Because of the Salton Sea's potential to produce a major earthquake and its proximity to population centers, it has become the focus of intense study in the past year by a research team led by Kent and Scripps geologist Neal Driscoll. The team is using specialized sonar techniques to map the hidden fault lines beneath the lake floor.  
In addition, they are digging trenches with colleagues at San Diego State University near Salt Creek to decipher the history of rupture exhibited in sediment layers. In addition, they are mapping topography at Mecca Hills with remote optical sensing equipment to measure the offset of gullies and streambeds to estimate the size, or horizontal displacement, of the past several large earthquakes. They are pinpointing how often seismic events have taken place throughout history, their horizontal displacement, and how the many lesser faults under the sea interact with the larger faults that bookend the region. And now California legislators and the state Department of Water Resources are among the parties interested in what the researchers discover. With some urgency, they are looking for ways to save the sea (see sidebar) and need to know what are the likely seismic scenarios for earthquakes rupturing through the Salton Trough. This water-starved, earthquake-prone region still needs the Salton Sea for several reasons, not the least among them being that the area is in the midst of a housing boom. Next page: Stretched like a Milky Way bar |
||
|
:: © 2009 Scripps Institution of Oceanography, University of California, San Diego. All Rights Reserved.
|
Terms and Conditions
|
||
