Saturday, November 3, 2012

Salton Sea Volcanics Part II

Writing this post became particularly challenging over the past two weeks--not due to any sort of technical information, but because of the memories this place conjures. Of all the places I've been (so far) I have stayed enamored with the Salton Sea and its small volcanoes. Perhaps because I was there Thanksgiving weekend of 1999 and the wide open spaces gave me the illusion of being one of the few cognizant souls in the world. Or maybe it was due to the companionship I enjoyed with my late husband.

I like to think it was because I stepped foot on the sandy soil and through a late morning fog, I gazed upon the volcanoes and felt myself transported back in time to some primordial landscape. The only sound was a gentle lapping of the sea against the gravel shore. No birds sang. No insects buzzed. The mountains on both sides were far away and to the south I sensed a vastness that would stretch all the way into Mexico. For the first time in my life, I felt at home.

Although I was well versed with the invertebrates of the Coon Creek Formation in West Tennessee, as a California transplant, unused to seeing volcanoes, I was overwhelmed with awe. This was a different kind of geology than I was used to seeing and I was hooked. I was determined to learn all I could about these volcanoes at Cal State Fullerton, and of course, all the reading I could manage on my own.

As we approached the southern end of the Salton, I noticed that the look and feel of the area was vastly different than the northern end. The latter was strewn in places with the bones of a dead community--the traces of a settlement that was never fully realized. But the south end was almost untouched by man and incredulity was so thick that one could almost brush it from the face with one's hand. Yeah, I was such the novice that I had regained the identity of the child within myself. If I could've drooled at that point, I would've.

But time was wasting and I wanted to investigate everything. Glenn walked the road up towards Rock Hill to see if my truck could make it and with his okay, we crossed over to my very first encounter with a volcano.
I climbed to the top quickly, all the while, taking in the landscape and scoping the lower regions for the mudpots I'd heard were there. Gulls began to crowd the shallows, looking for easy breakfast and then I saw Mullet Island. I realized that I had been privy to not one, but two volcanoes. Laugh if you will, but the experience was almost a revelation-an epiphany that brought every chart, diagram, and image in the pages of my books to life. 

The map showed a knobby outcrop back at the end of the road called "Obsidian Dome," which as I recalled was the third of my volcano adventure. Once I was there, staring up from the bottom at the blackness above, I knew I had to climb it. The thick rhyolite lava had jelled fast and plugged the hole from where it came, and the shapes were contorted into the most twisted and convoluted imaginable. Pumice lay around at various points and I pocketed the largest specimen into my backpack immediately.

But the farther up I went, the more obsidian I encountered. Of course, I had to bring home a piece of this, too, but I had to wrap it carefully else it would cut me three ways to next Sunday.

Glenn stayed at the bottom to give my shots a better perspective of my climb.

What a view! In the distance, the steam rose from the thermal energy plants that dotted the region and that made use of magma a mere 2 miles below us. Just be know that the crust is so thin here, sends a thrill up one's spine, along with the fact that even on top of this hill of glass, we were still below sea level.

But of course, the sun rose higher all too fast, and it was time to wend our way back. What was left to see was Red Hill and although we crossed the road (seen below) that transverses the shallows of the Salton, we decided that paying $2.00 per person was not worthwhile considering that we needed to head towards home. Still, I edged towards the shoreline in order to pick up pieces of Halite that fascinated me with their sheeting planes.

Notice the domes on Red Hill that constitute two former vents, as well as the oxidation that has taken place, giving the island its name.

One day, I'll take a flight out to Palm Springs and revisit this area that impressed me in so many ways, but until then, I'll keep this image close so that I never forget the haunted first look this place ever took within my very psyche.

~~Lin aka roxxfoxx

Friday, October 26, 2012

Salton Sea Volcano Mystery Solved

Moonset at Rock Hill, one of five volcanoes that comprise the Salton Buttes. The buttes last erupted between 940 and 0 B.C., not 30,000 years ago, as previously thought, a new study finds.
CREDIT: U.S. Fish and Wildlife Service
Earthquake swarms and a region-wide rotten egg smell recently reminded Southern California residents they live next to an active volcano field, tiny though it may be.
At the time, scientists said the phenomena did not reflect changes in the magma chamber below the Salton Sea. But now, researchers may need to revise estimates of the potential hazard posed by the Salton Buttes — five volcanoes at the lake's southern tip.

The buttes last erupted between 940 and 0 B.C., not 30,000 years ago, as previously thought, a new study detailed online Oct. 15 in the journal Geology reports. The new age — which makes these some of California's youngest volcanoes — pushes the volcanic quintuplets into active status. The California Volcano Observatory, launched in February by the U.S. Geological Survey (USGS), already lists the area as a high threat for future blasts.

"The USGS is starting to monitor all potentially active volcanoes in California, which includes the Salton Buttes," said study author Axel Schmitt, a geochronologist at the University of California, Los Angeles. "With our results, I think this will further enhance the need to look into the system," Schmitt told OurAmazingPlanet.

Schmitt and his colleagues dated zircon crystals in the hardened lava of the buttes with a relatively new technique, a "helium clock" that starts ticking once the minerals begin cooling at the surface.

Resolving the Obsidian Butte riddle

The revised age solves a long-standing archeological conundrum, said Steve Shackley, emeritus professor of anthropology at the University of California, Berkeley. Artifacts created from one of the five buttes, Obsidian Butte, first appear in Native American villages around 510 B.C. to 640 B.C. The Kumeyaay people, whose territory ranged from the coast to the Coso Mountains, crafted projectiles from Obsidian Butte glass, he said. "The men produced some of the best in the world," Shackley told OurAmazingPlanet.

Projectile point made from Obsidian Butte obsidian, collected west of Palomar Mountain in northern San Diego County, and attributed to the Luiseño cultural territory.
CREDIT: Janet C. Harvey/Axel Schmitt

 However, for decades, researchers thought Obsidian Butte erupted thousands of years earlier. To explain why no one collected the valuable obsidian, archeologists hypothesized that Obsidian Butte was submerged under ancient Lake Cahuilla, the precursor to today's Salton Sea. But geologists had long proved that Lake Cahuilla was ephemeral, flooding and emptying over and over again, so the explanation was always problematic.

"If this dating method is correct, then the Obsidian Butte material wasn't even available, and that makes more sense archaeologically," Shackley said.

Rifting brings rising magma

In fact, that Obsidian Butte rises above the Salton Sea is what first attracted Schmitt's attention. A 30,000-year-old butte should have been buried by a combination of sediment and subsidence by now, he said. "It had to be very young," Schmitt said.

The buttes exist because California is tearing apart, forming new oceanic crust as magma wells up from below. The sinking Salton Trough is the landward extension of the Gulf of California, and marks the boundary between the Pacific and North America tectonic plates.

The lava source for the volcanoes is a magma chamber beneath the Salton Sea, which also heats water for a nearby geothermal plant. Decay of uranium isotopes in zircon crystals show magma built up underneath the volcanoes for thousands of years before the latest eruption, the study shows.

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.

Schmitt said he hopes to study the area in more detail to better understand the most recent eruption. "The amounts of magma involved are relatively small and the impacts of an explosive eruption, meaning an ash cloud, would most likely be very local," he said. "We don't know very well how far any ash would have been dispersed, and that's something I would like to follow up on in the research."

Researching future hazards

The National Science Foundation's EarthScope project funds an extensive seismic imaging project in the Salton Sea that may soon reveal more information about what's happening deep underground.
"We'll be looking with great interest to see what we can tell from the Salton Seismic Imaging Project," said Joann Stock, a Caltech professor and an expert on the region's volcanic hazards who was not involved in the new study.

"I think [Schmitt's study] is a great contribution," she said. "It's an area where we should be concerned. We know that there's a lot of hot stuff down there," she told OurAmazingPlanet.
In August, an earthquake swarm shook the nearby town of Brawley. The USGS attributed the temblors to faults in the Brawley Seismic Zone. In September, a sulfurous stench emanated from the Salton Sea and wafted across the Inland Empire. The odor was tentatively linked to a fish die-off, but could also have been caused by volcanic gases, Stock said.


Wednesday, October 17, 2012

The Salton Sea Volcanics Part I

Recently, a small taped interview appeared on a San Diego news program that sparked some major interest in many. A geologist shot some footage from a chopper that hovered above the southern rim of the Salton Sea that clearly shows a pit of muddy water roiling like a witch's cauldron. The newscaster spoke of volcanic gases escaping to the surface (probably CO2 and/or H2SO4). This geologist stated that this area could be the setting for volcanic activity and that the USGS is keen on that fact. 

Since the time I bought my first real computer in 1998, and the following year as a geology major at Cal State Fullerton, I have known of the Salton Sea volcanoes. Every map of active US volcanoes that the USGS posts online displays the Salton Sea area as an active volcanic threat. And yet, how many people know or care about anything less than the size of Yellowstone or Rainier or Long Valley? Granted a number of factors would have to play into an eruptive episode for such a thing to be disastrous to the beach side meccas of Southern California; chances are that the Coachella and Imperial Valleys would be more imperiled than anywhere.

Inland Southern California is seductive-so much more than its beach front counterparts. As a recent grad in biology, with each trip past the southern mountain ranges I felt my grip lessen on the herpetological aspects of the desert and grasp more firmly on the stories within the strata of rocks. Never mind the close encounters with killer bees, sidewinders, and heat strokes; I had to be there every day off from work and school. But one area became an obsession: the Salton Sea and its inherent volcanoes. I would like to share that obsession with you of this primordial arena that holds so much mystery, more beauty than any work of art, and geological wonders beyond the imagination. 

But first, let's take a little earth history lesson on how this region was formed. Between 150-90 million years ago, the Peninsular Ranges, west of the Salton Sea, were formed from the same areal process that created the South American Andes, the Central American Cordillera, and the Sierra Nevadas: subduction. The Farallon Plate subducted beneath California and hot magma rose from that juncture to cool slowly into large plutons that became the Peninsular Ranges. Then about 30 million years ago, the North American plate overrode the Farallon Plate (aka the East Pacific Rise) and stopped the subduction of the Farallon. There are a few places where the remnants of that enormous plate still subduct, but for our purposes, we will focus only on what affects Southern California. The energy between the East Pacific Rise and the Pacific Plate was transformed (yes, I know, but it's a good pun) along a lateral fracture of the now buried East Pacific Rise and thus created the San Andreas Fault. 

However, do not discount the affect the still, very active East Pacific Rise has on Southern California. The EPR runs between Baja California and Mexico, separating the two and thereby causing a drop in the land where the Salton Sea lies. Molten lava rises along the break of the rise, causing older lava to be replaced by newer and spreading the older farther and farther from the rise itself. As stated, this spreading, conveyor belt of newly formed oceanic crust widens and thins the crust of the Imperial and Coachella Valleys. 
If you travel from Riverside, east on the 10, you'll soon come to the city of Banning in the San Gorgonio Pass. Banning is a small town that sits on the point of the "V" shaped gräben that comprises the previously mentioned counties. Traveling further east through Cabazon and into the heart of Imperial Valley, the elevation drops from 7oo' to below sea level in the city of Indio. This is the obvious change the East Pacific Rise has had on the suroundings, but there is an even more exciting transformation on the landscape: volcanoes.

Thanks to all that widening and thinning of the crust, magma can more easily find an avenue to the surface. There are five volcanoes or more precisely, five rhyolite domes at the south end of the Salton Sea: Rock Hill, Mullet Island, obsidian Butte, Red Island (Red Island has two domes). For the technical information, I turn to C. Dan Miller's thorough report (1989, Potential Hazards from Future Volcanic Eruptions in California: USGS Bulletin 1847) on the area; here are the specs: 

The Salton Buttes rhyolite center:
  • Most recent eruption: Silicic pyroclastic and extrusive eruptions at four vents approximately 16,000 years ago (Potassium-Argon dating);
  • Five silicic domes erupted;
  • At least one silicic lava flow associated with rhyolite dome;
  • Probable small-volume pyroclastic eruptions with tephra associated with dome emplacement at several vents;
  • No recognized debris avalanches or debris flows;
  • Most probably future potential hazard: Explosive and extrusive rhyolitic eruptions; phreatic and phreato-magmatic eruptions.
Although the youngest eruptions in this area are not known to have produced pyroclastic flows and surges, the compositions of lavas of past eruptions and the association of vents with ground water and the Salton Sea suggest that pyroclastic flows and surges and explosive eruptions could occur in the future. Such events commonly are destructive out to distances of at least 10 kilometers (6 miles) from an active vent.
 ... and from:  Robinson, Elders, and Muffler, 1976, Quaternary volcanism in the Salton Sea geothermal field, Imperial Valley, California: GSA Bulletin 87, p.347-360, March 1976 
The Salton Sea geothermal field lies in the Salton Trough, the landward extension of the Gulf of California, an area of active crustal spreading. The Salton Buttes volcanoes lie within the Salton Sea geothermal field where temperatures measured in wells drilled for geothermal brines range up to 360 degrees C at depths of 1,500 to 2,500 meters (Helgeson, 1968). The wells produce a hot brine containing up to 160,000 ppm of dissolved solids, chiefly Cl, Na, K, Ca, and Fe (White, 1968). Under the influence of this hot saline brine, the sediments of the Salton Trough are being transformed into metamorphic rocks of the greenschist facies (Muffler and White, 1969). 
From this information alone, one can see that even a phreato-magmatic eruption, an eruption that occurs when hot magma encounters saltwater, shouldn't be devastating to areas such as San Diego or Los Angeles. In short, lots of drama without a major impact other than on those living within the Brawley seismic zone, a large agricultural area south of the Salton Sea. The wind generally blows from the NW due to constriction via canyon walls; the ventifacts (rocks shaped by the wind) tell us that the wind has been blowing from this direction for many, many years. Also, west of the Salton, there is a field of Barchan Sand Dunes that attest to the strength of a wind blowing from one general direction.

South and East of the Salton Sea, one can find along dirt back roads, mudpots--some as large as 8' tall. Most are smaller and look much like crawfish holes dug out of Missouri gumbo (gumbo is a thick, gooey type of soil that contains rich sediments that enable the Boot Heel farmers to grow anything from rice to cotton to soybeans).  Near Frink and around Calipatria, there are many such mudpots bubbling and passing the pungent gases that are released from far below the soil.Even around Rock Hill, near the shoreline, the water bubbles as the Salton's water level has increased and has submerged the mudpots and hot springs.

Back to  Miller's report on volcanic hazards in the US, here is a graph from the same that outlines the potential area that would be affected by a future eruption and below this figure, there is an explanation for the type of hazard for this particular color coded zone.

Let's take a quick glance at the geothermal plants in the area:

From the Land Use Database, comes the following:

This cluster of seven geothermal plants is the largest of three major geothermal energy production sites in the Imperial Valley. A network of deep wells drilled in the geothermal field allow water, heated by the earth's mantle, to come to the surface and to power electrical generators. Owned by the CalEnergy Company, the electricity is sold to the local power utility and put on the grid. The seven plants in this field produce enough electricity to power over 100,000 homes.

In the next post, I'll go into more detail about the volcanoes, as well as to provide personal pictures taken on some of my adventures there. Stay tuned...

Lin aka Roxxfoxx

Friday, October 12, 2012

Lassen Peak Eruption Video - I'm not joking!

Last night I had one of the greatest of pleasures I can experience and that is to learn something that would be categorized as "the rest of the story. “Craig Martin relayed to me the tale of his grandfather, Justin Hammer, who lived near Lassen Peak in California in 1914. Hammer made his own camera and shot the following film at Catfish Lake, now Reflection Lake in Lassen National Park, in 1917, very near the north park entrance. 
Lassen's eruptions occurred from 1914 to 1917, but the USGS initially did not believe the eruption occurred on the earliest date. However, Hammer who lived so close to the volcano, witnessed the first eruption  in 1914.  Hammer would stay at his cabin unless heat, lava, and ash from the eruption forced him briefly away. Quite the adventurer, Hammer was the oldest man ever to scale the mountain's North Slope at age 70. 

Craig Martin comments, "National Geographic was sold the rights to the film in exchange for saving as much of the film as they could in the 60s. They found the film so brittle that when it was handled, it splintered into pieces. The film you see is all they could save of all the eruptions. The rest was explosive, so it was destroyed." The film was, at one time, over 20 minutes long. Prior to the eruption of Mt. St. Helens in 1980 this was the only film of a volcanic eruption within the continental United States. 
Craig has also promised me exclusive rights to his family archive of Lassen photographs; I simply cannot wait to see them. I am elated that Craig's and my paths have crossed and that along with making a new friend, we both can share a story that might otherwise not obtain the attention it so rightly deserves.
PS Audio was supplied by Craig, as the film was originally silent.

Remember the 2010 Baja CA Quake? Let's take a trip down Memory Lane...


Oct 11, 2012

The 2010 Baja California earthquake (also known as 2010 Easter earthquake, 2010 Sierra El Mayor earthquake, or 2010 El Mayor – Cucapah earthquake) was an earthquake of 7.2 magnitude on the moment magnitude scale. It started 26 kilometers (16 mi) south of Guadalupe Victoria, Baja California, Mexico, at a depth of 10 km (6.2 mi).

It occurred at 3:40:41 pm Pacific Daylight Time (PDT) on Easter Sunday, April 4, 2010, and it is said to have lasted about a minute and a half.

Brothers Roberto and Adrian Marquez were traveling in Mexico during that fateful Sunday and captured a surreal sight: The power of the quake lifting a layer of dust off a mountain range. The pictures show the area around La Rumorosa, the highest point in Tecate.

For more pictures of the quake’s damage by NBC San Diego, click here. You can also check out some incredible footage of the ‘earthquake mountain dust’ phenomenon in the video embedded below. You can also find the complete report by NBC San Diego here.

April_2010_Baja_California_earthquake_intensity_USGS.jpg(612 × 620 pixels, file size: 175 KB, MIME type: image/jpeg)

Sunday, April 1, 2012

Adventures in Fossils Part 1

It's been a while, hasn't it? Too long. Time to return to some new geo adventures that I've had. One adventure that I'm always game for is either rockhounding or fossil hunting. In fact, the best job I ever had was as an instructor at the Pink Palace's world renown Coon Creek Fossil Site. I had an inside on many of the native flora and fauna (give or take an epoch or two) and delighted in hunting for specimens at CC and also at a special Devonian site in middle Tennessee and the once world famous Cretaceous crab site in Selmer, Tennessee that is now covered by a very ugly arse Motel Six. Yeah. That's progress for you.

So this will be a two to three part post where I will display my most treasured fossils, and of course, I'll save the best for last. Let's begin.

These are a few specimens I collected while employed at Coon Creek. One of my duties was to explain to visitors how to clean and display their fossils. You always want to save the matrix that your fossil is embedded within, as that marl is 65 million year old beach sand. The unique feature about Coon Creek fossils is that the entire animal, including shells and bones, have been perfectly preserved within this waterproof aquaclude and you see it pretty much as it was when it lived. Of course, as Coon Creek was on the fringe of the Mississippi Embayment (Fig. 5), all of our fossils there are marine in nature. What you see above are as follows: Crassatella, Culcullaea, Turratella (long and tapered), Drillutra (snail), and ghost shrimp claws.

Above, are various Exogyra (primitive oysters), Pyncnodonte, Ghost shrimp claws and legs, Crassatella, Dentallum, Anteglossia, and a few snails.

The above is one of my most cherished possessions: a near complete crab from the Selmer crab site. The claws are to the left. The rest are halves or legs of those late Cretaceous crabs. This picture does not do these animals' justice.

That object in my hand is a rather large example of the Exogyra oyster from the late Cretaceous. And it's heavy. I have the complete oyster in my hand. They grew them rather large back then. :-)

Skipping over to my Middle Tennessee Devonian site, you can barely make out some of my Trilobites and fish bones. On the bottom left, you can actually make out Trilo-eyes; so far, the only one I managed to find to still have them. 

Various gastropods and molluscs are frozen in this Devonian limestone.

 Another trilobite-big one this time.

 More trilobytes, tube worms, and molluscs.

 Also Devonian, snails, molluscs, tube worms, and snail trails.

 On to California, where I collected these, I cannot tell, but these metamorphosed pieces were once a part of islands that lay alongside a future Orange County and were subducted along with the Farallon plate. These islands were ground up at the plates' edges and spit back to lie on the future shores of a beach. One of these rocks, the light green one, actually belongs with the two below. And their story follows...

And the caption says it all, except that the landslide was so powerful that the rocks from the top traveled halfway up the other side of a facing mountain. They're ugly, but they are some of the oldest rocks in California. 

 The rock on the left... it's volcanic and I found it in the San Gabriel's streambed. I'm still not sure what it is. Any ideas? Hint: it's not basalt. The red rock on the left is a chunk of chert taken from Rainbow Rock in the Santa Rosa Mtns. in the Colorado Desert. I'll post a picture of it's parent rock in a later post. It's huge.
 Garnet Hill is one of those odd places that lies between two faults just north of Palm Springs. The rocks on the series of low hills have some odd qualities, too. The above is one of my favorites due to its texture. It's soapstone and feels waxy to the touch and it's laced with garnets, hence the name of the hill.

Most of the above is basalt, with the exception of the Pyrite embedded in shale and the lapis lazuli in its pure form (2nd rock from the right). These items come from Hawaii, Columbia River plain, and Craters of the Moon Park. 

I have no idea where these two thunder eggs came from, but they were gifts and I certainly have enjoyed looking at them. I'm not sure, though, if I have more fossils than books or vice versa.

Part 2 and possibly a Part 3 next time. And we'll really get to the good stuff. Later!