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| Hand out of things to do from the info desk at the Salton Sea State Recreation Area. |
Slab City
Before leaving Salvation Mountain, we started the drive back into Slab City, just beyond Salvation Mountain. Slab City (or The Slabs) is a an off-grid community made up of boondocking RVers and squatters. Although occupied by only a few hundred permanent residents, Slab City swells to several thousand during the winter months due to wintering RVers.
The official Slab City webite has an interesting overview of the history of the location back to the 1930's. Slab City takes its name from the concrete slabs that remain from the abandoned World War II Marine barracks of Camp Dunlap. Camp Dunlap was a training center for Artillery Regiments and Anti-aircraft Units. Its relative proximity to the coast allowed planes to fly from aircraft carriers near San Diego.
It is hard for me to appreciate how much of the desert in this region was used by the military at different times, particularly during World War II. I was aware that Patton had used the region to train for the North Africa campaign, since we had seen the sign to the General Patton Memorial Museum while traveling along I-10 near Joshua Tree NP. However, it was only after doing some online searching that I stumbled upon how large his Desert Training Center was. Wikipedia indicates it extended west to east from near Pomona, CA to within 50 miles of Phoenix and from Yuma in the south into southern Nevada. I am sure that was mostly empty space then, but that is still an enormous area.
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| Detailed area map of World War II training center camps from BLM website: http://www.blm.gov/style/medialib/blm/ca/pdf/pdfs/needles_pdfs.Par.9550550e.File.dat/map2.pdf |
It is not clear to me how Camp Dunlap, which was a Marine base, fit in with the Desert Training Center, which was an Army facility, but it is certainly true there was lots of activity going on throughout the region. The Bureau of Land Management now controls much of that land and has an informational website.
But I digress.... Camp Dunlap was decommissioned in 1956 and ownership was eventually returned to the State of California, although California apparently didn't do much with it. Interestingly, the abandoned concrete slabs were first used as trailer pads by workers living on site while collecting creosote bush leaves. The leaves were sold to a chemical company that turned them into antiseptics and food preservatives. Slab City took on much of its present day character starting in the mid-1960's.
Given the late hour we decided there was not much we really wanted to see. We turned around before going back into Slab City proper, then again headed south on Route 111.
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| Map from the Sonny Bono Salton Sea National Wildlife Refuge brochure |
Strangers in a Strange Land
Bombay Beach, Salvation Mountain, Slab City, and even Niland seemed other worldly. That strangeness was due mostly to the different lifestyles. However it was also the geography. It is dry and dusty, but we were particularly struck by the flatness of the terrain. The entire area is a broad, basin with little or no topographic features. This is the result of the fact that the Salton Trough has been a lake bed on and off for thousands of years. Were it not for the 30 foot high ridge of sediment from the Colorado River southeast of Mexicali (relocated fill from Canyonlands and the Grand Canyon?), the Gulf of California would extend into the valley and Palm Springs would be a saltwater fishing village!
However it is not just the flat, dry terrain. Even more interesting is what is going on below the surface. It has generally been accepted that the San Andreas Fault ends about 2.5 miles north of Bombay Beach (although very recent research reported here or here suggests the fault may extend south of the Salton Sea). South of Bombay Beach to roughly Brawley is the Brawley Seismic Zone. Within this is the Salton Sea Geothermal Field. This is evident in many different above ground features. I especially liked this description from a 1948 article in The Desert Magazine which still holds true today:
Rocks that float, mud that boils, gas that makes dry ice, springs that flow paint--these are just a few of the many strange freaks Nature has contrived for those who take the field trip
In hopes of seeing some of the features listed near the shore of Salton Sea, we turned west on Sinclair Road. Along the southern shore are several wildlife areas, including two units of the Sonny Bono Salton Sea National Wildlife Refuge. The volunteers at the visitor center (end of Sinclair Road) were lowering the flag just as we drove in, so we only asked for directions and kept on moving. However this would definitely be worth a stop in the future. We could see a raised stand for viewing wildlife and there are also trails.
Geothermal Plants
As we drove in this area we passed multiple large geothermal plants. The Salton Sea Geothermal Field is a rift region, i.e. the continental plates are spreading and the earth's magma is not very deep, only 5-7 miles below the surface. The geothermal gradient here is 140 to 1300°C/mile, compared to a more typical 40°C/mile. It is this high heat at relatively shallow depths that has resulted in ten or eleven geothermal electrical generation plants in the region, the most recent of which came on line three years ago.
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| The Hudson Ranch I plant, from UT San Diego article upon the plant's opening in 2012. |
This geothermal field was slow to develop due to the high concentration of chemicals in the hot brine that was pumped to the surface and used to run the turbines when it turned to steam. It took years of research to solve the problems with precipitation of the dissolved solids which clogged pipelines. One solution is to remove the dissolved solids. The recovered materials, and especially lithium, may have additional economic value. It is reported that Simbol Materials, the owner of a lithium recovery plant in the region, has been in talks with Tesla Motors, which needs large amounts of lithium for their "Gigafactory" for lithium batteries.
Whatever the future, these geothermal plants dominate the region along the southeastern shore as you drive around the area. Their smokestacks give off steam and there are many large pipes running above ground along side the road. It was amazing to see all of these. I don't know if they provide tours to the public, but I stumbled across a series of pictures from this person's tour several years ago.
Mud Volcanoes and Mud Pots
Other examples of the geothermal activity are the multiple mud volanoes and mud pots in the region (see this geocache for mud pot coordinates). We saw some of the mud volcanoes from a distance in a field north of Sinclair Road, but did not stop. Enough carbon dioxide bubbles to the surface that it used to be harvested for dry ice. This article published in 1948 in The Desert Magazine, has some of the most detailed info about the dry ice plants:
Late in 1932 a well was drilled east of the mud pots to tap the carbon dioxide gas which oozes to the surface there. Productive gas sand was struck 600 feet down, and the sand was found to be 35 feet thick. In 1942 there were 15 producing wells in the area and there was a dry ice plant at the field and another at Niland. Gas was piped to Niland through 3 1/2 miles of 4 1/2 inch pipe, to the plant of the National Dry Ice Corporation. At Niland the carbon dioxide gas was compressed and liquified. Twenty thousand cubic feet of the gas were required to make one ton of dry ice and the plant was capable of making 25 tons a day. National Carbonic Products had eight producing wells. The plant of the company located in the field had a capacity of 20 tons per day. Today that plant has suspended production and is falling into ruin It can be seen beside the road that leads to the mud pots, with the capped wells fizzing noisily.We did not see the abandoned dry ice plant, but it is apparently still there, with multiple pictures on the web and even a nearby geocache.
Salton Buttes
One of the most interesting features of the geothermal activity is a collection of five small lava domes along the southeastern edge of the Salton Sea known as the Salton Buttes. The Salton Buttes, which to the untrained eye are four rather unspectacular looking small hills, include: Mullet Island, Obsidian Butte, Red Island, and Rock Hill.
Long thought to have last erupted tens of thousands of years ago, very recent new research now puts that last eruption at only 2000-3000 years ago. This more recent date moves these lava domes to active volcano status, the only active volcanoes in southern California, and makes them of much greater potential threat. However, any eruption is not likely to be of the St. Helens variety. As noted in this article:
If another eruption occurs at the Salton Buttes, it will likely mimic past breakouts, Schmitt said. The volcanoes are made of sticky, slow-moving rhyolite lava. At Obsidian Butte, the lava cooled so quickly it turned into glass. However, pumice and ash found nearby means past breakouts started with a bang.Obsidian Butte is primarily obsidian, but with lots of pumice in the area. I had read earlier about this cache on Obsidian Butte and how much people enjoyed seeing this area, so we made an attempt to drive back to Obsidian Butte. It was a fairly good unpaved road, but it deteriorated near the hill...not the best of locations for Geo-Audi as we almost found out the hard way. We turned around without getting out of the car, but still managed to pick up a piece of gravel that made all kinds of noise until we could dislodge it.
Algones Dunes/Imperial Sand Dunes Recreation Area
We really were running out of daylight now, but there was yet another interesting sight along the route before it got completely dark...the Algones Dunes. The Algodones Dunes is a large sand dune field. The field is approximately 45 miles long by 6 miles wide and extends along a northwest-southeast line that correlates to the prevailing northerly and westerly wind directions. We could see it for many miles as we drove along Interstate 8 just north of the Mexican border. The name "Algodones Dunes" refers to the entire geographic feature, but the portion administered by the Bureau of Land Management is known as the Imperial Sand Dunes Recreation Area. I don't know if they were only on BLM land, but we saw many people with off-highway vehicles (what I would have called "dune buggies"). It is pretty "other worldly" looking, hence not surprising that this was the site where the Tatooine scenes in Return of the Jedi were shot.
Telegraph Pass
We saw very little of Yuma in the twilight as we snaked our way through on the interstate, but we did experience the precipitous drop (at least by interstate standards) on Interstate 8 through the Gila Mountains east of Yuma...Telegraph Pass. This entry from Wikipedia describes it this way:
One of the oldest sections of the Interstate Highway System in the US goes through a two-tiered highway section through Telegraph Pass at the north end of the range. The I-8 roadcuts in this area of Telegraph Pass expose some of the oldest metamorphic rocks in the state of Arizona, outside of rocks exposed at the bottom of the Grand Canyon.I definitely want to go through here again in the daylight.
By the time we made it past Telegraph Pass it was completely dark and we saw nothing of the scenery into Gila Bend. However, coming this way (vs coming across on I-10) did seem to reduce the amount of traffic and we successfully made it to our usual first night stop on the way home, the Best Western Space Age Lodge in Gila Bend before it was too late. The Space Age Lodge is a weird place, but fun in a funky way. In any case, it was the end of a very busy day.
