SAN ANDREAS FAULT


October 16-17, 2010
By Nan Savage

The following participants met in downtown Brawley at 8:30 a.m. at the gazebo: Jean and Mal Roode; Rick and Sharon Cords; Bob Rodemeyer; Brett and Cristina Henrich; Joe de Kehoe; Barbara and Ron Midlikoski; Leonard Friedman; Ding and Allan Wicker; and Johann Inisan, an exchange student from France who is staying with the Wickers. Johann was particularly interested in the terrain we visited, commenting that “there are no deserts in Europe.”
We began the day with an introduction to the geology of the San Andreas Fault zone given by geologist and DE member, Joe de Kehoe. Joe pointed out that we often speak incorrectly of an earthquake “fault line;” in fact there is no fault line, but rather a “fault zone” or numerous “fault tracings.” The San Andreas Fault is, of course, the point where the Pacific and North American plates intersect, with the two plates shifting approximately 2 inches per year. At its southernmost end, the San Andreas Fault cuts through the Coachella Valley. The Coachella rests 273 feet below sea level. In contrast, at its deepest point (286 feet below sea level) Death Valley falls only 13 feet beneath the Coachella.
Our first stop was Obsidian dome, a volcanic cylinder which offers a stunning view of the Salton Sea. We scrambled up its obsidian rocks and looked out across the most unusual inland sea. Ten thousand years ago, the Colorado River, unhampered by human intervention, emptied itself completely into the Gulf of California. Periodically, however, the river would naturally backup and fill up the Salton Sea basin, forming a temporary lake. Over centuries the lake became salty from the minerals that leached out of the sediments in the region’s rocks and springs. The lake alternatively filled up and dried up according to the seasons of the Colorado River. The basin did not receive enough precipitation on its own (only an average of three inches per year) to maintain a year round body of water. However, in 1906 engineers decided to build a canal to divert some of the water from the Colorado for irrigation and habitation. During the project, an accident occurred, and the dam holding back the full force of the Colorado River broke its banks, allowing water to flow unimpeded into the Salton Sea region. Eventually, railroad crews stopped the cascading flow, but by then enough water had accumulated to create the present day Salton Sea, a year-round inland salt water lake. Heavy run-off from irrigation in the surrounding area continues to ensure the Sea’s existence. In fact, during the 1970’s and 1980’s the run-off from nearby agriculture was so heavy that the Salton Sea rose substantially. But by the 1990’s, because growers had adopted more water-efficient drip irrigation systems, the water level of the Salton Sea dropped, leaving today a smaller Sea with a tremendously high concentration of salt, currently 30% more intense than the Pacific Ocean. As a result of such high sodium concentration, much of the animal life in the Salton Sea has died off.
Next we journeyed to the Sonny Bono National Wildlife Refuge. Erik, the Refuge Manager there, who is akin to a ranger, explained the Refuge’s purpose. He said it serves as a way station for birds travelling south along their annual migratory routes. The first Wildlife Refuge in the area was established in 1930 by President Hoover, on 30,000 acres, but over time as the Salton Sea grew the Refuge became submerged under water. The present-day Refuge comprises only about 2,000 acres, and is located on land leased by the government. But it continues the tradition of providing a resting place for migratory birds. Civilization and agriculture have reduced their previously open habitats; so birds find fewer spots to stop and feed. Managers at the Refuge sow annual rye grasses for their migratory visitors, particularly wild ducks and geese, and preserve for them the few remaining cattail marshes in the region. Birders can watch annual migrants from a specially designed birding perch on the property. Interestingly, the Refuge also permits hunting, so a significant number of migrating birds have learned to pass it by, as they like us, do not enjoy frequenting restaurants where drive-by shootings are a regular occurrence!
Next we visited two geothermal sites created by their proximity to the San Andreas Fault: the Mud Volcanoes and the Mud Pots. By way of explanation, seismic faults cause both mountains to rise and “valleys” to sink. While true geological valleys are caused by the erosion of water against rocks, valleys caused by seismic faults are sunken terrains, actually created by the downward action of tectonic plates. In these low-lying areas, the molten core of the earth rises up close to the ground’s surface, and usual geothermal activity will result.
The Mud Volcanoes are located off of a dirt road on private land. They are eerie, other-worldly creations of nature, small but oddly shaped mud cones that rise a few feet in height, omitting strange hissing noises from their bubbling centers of mud and steam. They resemble the small cartooned volcanoes drawn by the French writer, Saint Exupery, in his classic illustrated children’s book, The Little Prince. Periodically a burst of spray emerges from the core of these miniature volcanic cones. Archaic peoples regarded such cones and their larger volcanic cousins as natural entrance points to the mythical underworld, openings where either dark spirits or spirits of the dead might unexpectedly emerge.
A few miles down the road, we made another stop at the Mud Pots, a similar center of visible geothermal activity, but with configurations of sunken holes rather than mud-rising volcanoes. Huell Howser produced a PBS show on both the Mud Volcanoes and the Mud Pots, and ironically it encored the very night that we returned from our trip. Huell, like us, found the mud surrounding the geothermic volcanoes to be deep, thick and gooey. My daughter, Kathryn, a Geography major at UCLA, researched the mud volcanoes by searching available US Geological Survey maps, and found that the Mud Pots and the Mud Volcanoes are actually two examples of a number of such sites in the immediate vicinity, all of which are documented on US Geological maps. As a result of such strong geothermal activity, several commercial power plants are now harnessing this natural earth-powered energy.
Next, we drove on to the Salton Sea Visitors Center where we took our lunch. We picnicked at tables with attractive wooden shade covers along the edge of the Salton Sea. After lunch several of us watched the informative film in the Visitors Center, while others explored the “seashore.” The sand by the Salton Sea is composed of millions of tiny broken seashells, not grains of sand formed from rocks which one is used to at ocean beaches. Unfortunately, the seashore was also strewn with the carcasses of thousands of dead fish, perhaps a result of the Salton Sea’s high salt content. Pelicans, however, seemed happy to swim along the surface of water.
After lunch, we journeyed through several nearby residential neighborhoods, tracing the Fault zone as it passed furtively under privately owned residences. We wondered how many of these homeowners knew their homes sat on a precarious geological state of affairs. Indeed, further north, much of the City of San Bernardino is quietly built along the fault zone. Evidently, it is rather difficult to see the Fault at eye level, but much easier to discern it from the air. A device such as Google Earth makes tracing the fault zone easier.
In other areas, however, the Fault’s existence is very visible from the surface of the earth. We visited one such site next, the astonishing Painted Canyon. It provides a spectacular view of the active collision of the North American and Pacific plates. In the Canyon intersecting sedimentary rocks are twisted, turned over, and laid flat by the potent butting together of the two plates. Because the rocks are composed of various colors, they readily display distortions caused by the action of moving landforms. Rocks which were originally laid down horizontally are now totally up-ended and thrust vertically into towering spears and dramatic arches. Rick began to ask Joe a hypothetical question about the amount of time it would take for such geological formations to take shape, beginning his question with, “If I were to sit here for a million years, how long….” But before he could finish his sentence, other members had piped in with advice for him about how many beers he would need to stock up on and whether a comfortable lawn chair would be in order for his million year wait!
After Joe’s talk on the geology of the area, some members of the group decided to hike up Ladder Canyon, which rises out of the end of Painted Canyon. The way leads into a slot canyon which can be approached only by ladders which have been left in place for that purpose, hence its name, Ladder Canyon. Leonard, who had been up the canyon before, shot a video of the group hiking and showed it to several of us later. We drove on to the town of Indio, where we checked into our motel rooms and assembled for dinner at Pueblo Viejo, a surprisingly superb Mexican restaurant located in an unlikely cuisine capitol.
Sunday morning we arrived at the Coachella Valley Preserve, once known as “Thousand Palms.” In actuality, there are only a few hundred palms at the site, but they are massive, and especially unique, not for their numbers, but rather for their being native to the area. Most of the palm trees in Palm Springs, and throughout Southern California for that matter, were artificially planted, put in by land developers because their exotic look successfully attracted people from the East Coast. The palm trees at the Preserve, of the Washington filifera variety, are unique because they occur naturally. The Fault zone under the Preserve brings needed groundwater close to the surface - a mere 8 feet below the soil line - thereby giving the palm trees the water they require for their shallow roots. Furthermore, we learned that palm trees are not really “trees” at all, but rather very tall grasses. Their skirts act as important homes for a number of desert animals, including the rare nocturnal Southern Yellow Bat.
The Coachella Preserve was originally a homestead; its distinctive hand-built palm house still stands now as the Visitors Center. It is a small log cabin built of palm trees, but with the palm trunks running vertically rather than horizontally as one is used to seeing in the familiar log cabins made from wooden forests. The hand-crafted home is quaint and charming, a true example of American folk art in the desert. A cafe flourished here at one time and cabins were built in the back to house overnight guests at 25 cents a night. We walked along the McCollum trail, which makes a circle around the Preserve, roughly tracing the path of the San Andreas Fault.
Leaving the Preserve, we drove on to our next stop, the site of the giant wind turbines which one normally sees only from a distance while traveling along interstate I-10 through Palm Springs. Standing up close to these giant machines, one feels their immense power - they are truly daunting titans - generating overwhelming energy similar to a jet engine, but from only the wind. We continued to drive along a dirt road, crossing the White Water River, which is an unexpectedly large and swift year-round desert river. It led us up to the newly created Whitewater Preserve, where we ate lunch and officially ended the trip, leaving participants free either to get an early start home on the freeway or to hike and explore the newly protected White Water Preserve.
The trip gave us all a richer and more detailed understanding of the intricacies of the southernmost section of the San Andreas Fault zone as it passes through a variety of geological formations. We gained new insight into the earth’s mysteries.