Saturday, September 29, 2018

The Many Sides of California's Incredible Composite Cone Mt. Shasta

Hotlum Cone and Shastina, the two youngest cones of Shasta are seen here from the north on Highway 97

California has a lot of incredible volcanoes, but looming above them all is Mt. Shasta, the huge composite cone that rises above the mountains of Northern California. At 14,179 feet, it towers over all but a few of the highest peaks of the Sierra Nevada, but none of them are close by. It is more than a mile higher than any other nearby peaks. I and my students have been traveling around it the last two days, and we've seen it from every side.

From the south it was largely hidden by the smoke from the recent wildfires, but we drove up the Everritt Memorial Highway to the 8,000 foot level at Panther Meadows. The barren valley once hosted a ski resort until folks realized the lack of trees in the area was because of the constant avalanches. The ski area was moved, but the road remains, and serves as a high trailhead for summit attempts.
The Sargent's Ridge and Misery Hill cones of Mt. Shasta. These cones are older and more deeply eroded.

A careful study of the ridges and valleys reveals that there have been more than one "Shasta". At least five volcanoes have developed over the Shasta magma chamber, but most of them have been removed by erosion, explosion and avalanche. Only the highest cone, Hotlum, and the satellite summit of Shastina seem untouched by serious erosion. They are both less than 10,000 years old, and Hotlum has continued to erupt at intervals of several hundred years.
From the northeast, Shasta is highly symmetrical. That large snowfields remain in the fall season is evidence of the presence of glaciers. Shasta has at least five of the them, and Whitney Glacier is the longest glacier in all of California, at two miles.

The peak shined bright and clear in the morning light, but by this evening, it was shrouded in clouds and lightning was flashing in the skies above. The mountain, a so-called composite cone is a mountain of many moods.

I'm pretty sure I don't want to see the mountain angry...

Friday, September 21, 2018

Recalling California's Second Worst Disaster Ever: The Victims May Finally Get a Voice

A number of people have brought to my attention this article in the Press Enterprise about efforts to construct a memorial to the victims of the St. Francis Dam disaster. Such a memorial is long overdue. I tell this story at the beginning of every one of my classes, and in thirty years, not one student had ever heard of it. I'm reposting my January 2012 blog on this disaster below. Thanks to Representative Steve Knight and Senator Kamala Harris for sponsoring the bill that establishes the memorial, and Dianne Erskine-Hellrigel, the local community organizer who is leading the efforts to raise funds for the memorial. If you wish to donate, contact the St. Francis Dam National Memorial Foundation, c/o Dianne Erskine-Hellrigel, 24820 Fourl Road, Newhall, CA.
Hindsight is harsh.

Sometimes choices and judgements are made to save time, to save money. Sometimes choices are made in unfortunate ignorance, in a time when no one could have foreseen or recognized the right choices to be made. Sometimes there is no one there to provide perspective, to provide alternatives. And then people die. Lots of people.

Ask folks what they think was the worst disaster in California history and many will get it right. Upwards of 3,000 people died in the 1906 earthquake in San Francisco, and the event has shaped the psyche and attitude of many people in the state more than a century afterward. And it was brought about by a natural event.

The second worst disaster in the history of the state is far less known. Some might guess another earthquake, like the Long Beach quake of 1933 (115 dead) or the Loma Prieta earthquake of 1989 (63 dead). Historians might point to the Port Chicago munitions explosion of 1944 (320 dead). Few people are aware that it was the collapse of a dam, and that the collapse was the result of many poor choices. Hindsight is a harsh judge, but many of the mistakes were "before their time" so to speak. The fact that it happened maybe has prevented worse disasters in the intervening years.

Time (and a great deal of government effort) has erased much of the record of our state's second worst disaster. As far as I could see there is not a single plaque or monument, either concerning the horrific event, or commemorating those who were lost. There is a small cemetery where some of the victims were buried.

Looking at the slide area on the left side of the picture above, it is hard to believe that a 200 foot high dam was anchored there, in the incompetent mica schist. It is hard to believe that the failed slopes in the picture obscure an even deeper and bigger megaslide.
It is hard to look at the flat ridge on the right side of the picture above and realize that no one ever thought to check the effect of soaking the seemingly solid conglomerate in water. It is glued together primarily with gypsum, a mineral that dissolves in water. The rock falls apart when saturated.

Maybe the most stunning realization is that the schist and the conglomerate are separated by a fault zone. An inactive fault by all appearances, but a fault nonetheless. They built the dam on a mega-landslide, and on a fault zone.
It is difficult to envision that on the night of March 12, 1928, the recently completed dam failed so catastrophically that the floodplain in the photos above and below was inundated with 140 feet of water flowing at a rate of 1.7 million cubic feet per second (California's biggest river, the Sacramento, averages 30,000 cfs, and the record flood on the river was 650,000 cfs).

What happened?

As Ron and Randy correctly surmised, Friday's mystery photo was about the destruction of the St. Francis Dam in 1928. I consider it one of the most important geological events ever to happen in the state, not because a great many people died, but because they died as a result of a disregard or lack of knowledge concerning human construction projects and the geological foundations on which they are built. Earthquakes and volcanic eruptions are inevitable geologic events, but the events of 1928 were completely avoidable.

In the early twentieth century, Los Angeles was at a crossroads. The city was growing fast, and the water needs of the metropolis far exceeded locally available supplies (according to city officials anyway). The story of how the city stole (legally stole, but stolen nonetheless) the water from underneath the people of the Owens Valley is a legend of California history. The fact that much of the water went to irrigation in the San Fernando Valley instead of the city just added to the scandal. Having completed the Owens Valley Aqueduct, one of the largest public waterworks ever conceived, the city needed someplace to store the water locally, especially in preparation for drought conditions. William Mulholland, the superintendent of the predecessor to the Los Angeles Department of Water and Power, oversaw the design and construction of a series of reservoirs around the Los Angeles Basin. Nine were constructed, and St. Francis Dam in San Francisquito Canyon above the Santa Clarita Valley was the largest, with a storage capacity of 38,000 acre feet. The dam itself was about 200 feet high, and just over 600 feet across. It was a concrete gravity-arch dam, one that depended on the nature of the rock in the abutments to maintain stability.

Construction was begun in 1924 and complete in 1926. During the construction Mulholland directed that the dam be made 20 feet higher than in the original plans, but he made no alterations at the base to compensate for the additional weight of the water. The filling of the dam took another two years, and was complete on March 7, 1928. On the morning of March 12, the dam keeper noted a leak of muddy water and alerted Mulholland. Small leaks of clear water from dams are usually expected; muddy leaks from a dam are very bad.  Mulholland declared that the mud was from some recent road construction and that the dam was safe. 12 hours later, the dam keeper was dead, the first victim of the collapse of the St. Francis Dam. In the hours that followed at least 600 more lives were lost.

To his credit, Mulholland took the blame for the disaster. Although he was never convicted of any crime in the matter, his career was over. He died seven years later.
Accounts at the time suggested that failure occurred as water channeled through the conglomerate along the fault contact. A reassessment of the failure by J. David Rogers finds multiple causes for the disaster, with the reactivation of the ancient landslide being the most important factor, along with hydraulic lifting of the dam which was caused by water pressing against the topmost part of the dam (which had been made higher without compensating at the base). Rogers lists many other deficiencies, including the weakness of the rocks in the dam abutments (I refer interested readers to this very fascinating pdf by Rogers that provides a blow-by-blow analysis of failure of the dam and a great deal of background information on the disaster).

Incredibly, despite the total evisceration of the dam, the central part remained standing, a 200 foot high monument to the destruction. After a sightseer fell off the top (his "friends" had tossed a rattlesnake at him), the city quarried holes in the base, filled them with five tons of dynamite, and blew up the remaining tower. Other blocks were also destroyed, as if they were trying to erase all memory of the event. One of the blocks was the "outcrop" I used in the Friday mystery photo.
The U.S. Geological Survey has a (much appreciated) photo archive from which I have gathered these photographs of the aftermath. In the photograph below, the fault line dividing the Vasquez Conglomerate from the Pelona Schist can be clearly seen (the lighter Pelona in the foreground, the dark Vasquez on upper ridge). The fault is inactive, and no earthquakes are implicated in the failure, but had the dam not failed, rising water pressure along the fault could conceivably have eventually caused renewed quake activity. The phenomenon has been noted elsewhere.
Blocks of concrete weighing thousands of tons were carried in the floodwaters nearly a half mile downstream. The magnitude of the disaster is hard to comprehend. Normal rivers have trouble moving boulders only a foot across. Besides the sheer magnitude of the flow, debris from the landslide buoyed up the blocks.
The block below was a half mile downstream. It measured approximately 63 feet long, 30 feet high, and 54 feet wide.
It is hard to find much that is positive in this disaster, but changes were made in the aftermath. The input of qualified engineering geologists became a requirement in dam-building, and much more attention was paid to the geological setting of reservoir sites. Boulder Dam on the Colorado River, one of the largest dams in existence is not in Boulder Canyon. Following the St. Francis disaster, the site of the dam was changed to Black Canyon when it was decided that the rocks that would anchor the dam were more stable there.

It would not be at all correct to say that we learned every possible lesson in dam construction. The 1963 tragedy at Vaiont Reservoir in Italy and the 1975 collapse of the Teton Reservoir, Idaho are vivid examples of unlearned lessons.

Hindsight is harsh. But it can be a teacher, too.

Tuesday, September 18, 2018

Here's a Pretty Puzzle...What are These Trees Doing Here? An Evening at Calaveras Big Trees

When the trees were discovered by people of European descent in the 1850s, few believed the stories of their immense size. There were of legends and tall tales emerging from the explorations of the American West, but trees that towered 300 feet high with diameters of 35 feet just seemed beyond the pale. Eventually promoters stripped the bark off one of the really big ones, took the pieces to an exhibition back east and reconstructed the tree. Many still considered it a hoax anyway.
The poor tree that was stripped still stands today, a dead snag in the Sequoia Grove at Calaveras Big Trees State Park in the northern Sierra Nevada along Highway 4. I didn't get images of that tree, but there were plenty of other living ones to enjoy. We were there the other day on a lark. We had a couple of hours to see the sinking sun and lengthening shadows in the forest before a late dinner in Angels Camp.
The Sequoia Trees (Sequoiadendron gigantea) are an enigma. They exist today only in a series of 65 individual groves scattered across mainly the southern Sierra Nevada. They are relatives of the Coast Redwoods, and the Dawn Redwood of China, a tree that existed in a single grove which was only scientifically described in the 1940s. Yet the trees have existed since the age of the dinosaurs and were once distributed widely across the northern hemisphere. Their Sierra home is their last refuge. About half the original Sequoia trees were cut down prior to receiving protection, but because the wood was brittle and tended to shatter, they only found use as grape stakes and the like. Nearly all the remaining trees are protected, either in Sequoia/Kings Canyon National Park, Yosemite National Park, or Giant Sequoia National Monument.
Aside from human attack, they are not easily killed. Their bark is thick and lacks easily burnable sap so most wildfires don't hurt them (high burning "crown" fires are an important exception). The bark is thick, keeping them safe from insect attack. The trees are thought capable of living more than 3,000 years. Their greatest liability is a shallow root system that lacks a large taproot, so they can topple on uneven slopes or during intense windstorms.
The cool mystery about these trees is the one of their biogeography. How did they get to where they are today, and how did they survive when most of their closest relatives did not? Calaveras Big Trees is an even greater mystery, along with a small grove in Placer County consisting of a mere six mature trees. Looking at the map below, one can see their isolation from the others of their species, more than fifty miles of deep gorges and canyons.

At least one part of the explanation is clear. They migrated over the Sierra Nevada crest. Every time I say that I envision the gigantic trees walking like some of Tolkien's Ents, but it is better to see them as propagating along pathways where seeds could thrive and grow. This would be impossible with the present day Sierra, given the crest topping out at elevations over 10,000 feet. But the Sierra Nevada is a young mountain range, and it's probably only been a few million years since the range rose and tilted to the west (opinions on this scenario, it should be noted, vary). The trees that once thrived across Nevada had an uninterrupted slope towards the west. As the mountains continued to rise, they cut off the precipitation into Nevada's Basin and Range Province, turning the region into the semi-arid and desert environment that it is today.
Perhaps the main factor in the decline of the Sequoia trees across the hemisphere was the Pleistocene Ice Ages. A dozen times or more the ice advanced and receded across the northern parts of the continents and in the high mountains. The habitat for the trees was simply erased across much of the former range and the trees couldn't propagate quickly enough to escape the ice. In the Sierra Nevada, however, the unique geography, the westward tilted block of rock, probably saved the trees. When conditions grew colder, the seeds could propagate in soils lower on the westward slopes, and when the ice receded, they could propagate uphill.
Still, one has to wonder what the Calaveras grove is doing here, fifty miles north of their relatives in Yosemite National Park (who are in turn fifty miles north of the bulk of the Sequoia groves). And those six mature trees in Placer County? How have they survived? For the record, there were historically eight trees, but two fell in 1862. It's a pleasant mystery to contemplate as one wanders through the two beautiful groves at Calaveras.

Friday, September 14, 2018

Fall in the Great Valley: A Colorful Treat

I admit that California's Great Valley is sometimes a drab place. In the late summer, the almonds are being harvested, and the process involves the production of vast amounts of dust. The air is stagnant, trapped between the Coast Ranges and Sierra Nevada, with few winds to clear the skies. For weeks at a time, I won't be able to see either mountain range. And the sunsets are generally unremarkable affairs that are totally easy to ignore.

As the fall season approaches, things start to change a bit. For months we have been trapped beneath the subtropical belt of high pressure, a global circulation pattern that blocks rainstorms from reaching California. Little or no rain will fall from May to October. But when we reach September, the first tentative low pressure systems start to rotate out of the northwest, bringing no precipitation but the breezes start to clear out the dust and smoke. And the first cloud banks start to appear.
The sky was a real treat tonight. For the last few days we've had some high puffy cumulus clouds in the upper atmosphere, and on Thursday morning I spied the Coast Ranges and the Sierra Nevada as I climbed the outdoor stairs to my office. And tonight the clouds blazed forth in full glory as the sun sank deeper below the horizon. The white light was refracted through air layers on the horizon and broke up into shades of yellow, pink and red.

I know there are lots of places where spectacular sunsets are a way of life. The Oregon coast, Tucson, and Maui come to mind out of my own experiences. But there is something a little special about seeing a spectacular sunset like this in a place where they are precious and few.

Tuesday, September 11, 2018

Want to See Some Incredible Volcanoes Up Close? Geology of California's Volcanoes, Sept. 27-Oct. 1, with Modesto Junior College

I write so much about my travels around the American West and elsewhere, and some might wonder where I find the time. Well...I tend to have a group of students with me. Geology, perhaps more than any other science, is best learned in the field, and our school recognizes the importance of field experiences. The community college system in California is of course one of the best alternatives for beginning a college education, a gateway to transferring into universities, but we also recognize lifelong learning as a part of our mission. Education doesn't just end with a degree. Professionals in one career can benefit from courses in related disciplines as a way of improving their job performance, or advancing up the pay scale. And all citizens can benefit from becoming better informed on the political issues of the day, such as climate change, or energy development (pulling some examples from geology).

With this in mind, I wanted to let my Modesto area-based readers know about some great field studies trips coming up this fall. On September 27-October 1, I'll be teaching Geology 185, the Geology of California's Volcanoes. We'll be exploring Mt. Shasta, Lava Beds National Monument, Medicine Lake Highland, and Lassen Volcanic National Park, as well as Castle Crags and McArthur-Burney Falls State Parks. We will be camping at Woodson Bridge State Park the first night, spend two nights at Lava Beds National Monument, and the last night at McArthur-Burney Falls State Park. There will be hiking and caving opportunities, and some simply incredible scenery among some of the youngest volcanic features in the western United States.

If this sounds intriguing, you can find more information at California residents pay the normal tuition rate (2 semester units), but the rate is higher for out of state participants. The $80 fee for the course covers the van transportation and fees at the various parks and campgrounds. The students provide their own food (we'll have stoves and fuel). For my local readers, we'll have an organizational meeting on Thursday, September 13 in the Science Community Center at Modesto Junior College, room 326, at 5:30 PM. Contact me if you have questions.

Tuesday, September 4, 2018

Isn't All Geology in the Field? Well, Here's an Exciting Field

There's an ugly vacant lot adjacent to the Science Community Center at Modesto Junior College (the science lab and museum where I work). It's been collecting weeds and litter for years, and some administration officials a few years ago wanted to plant it with grass, and some even suggested making it a parking lot. Maybe there is a little bit of logic to that, given the impacted parking situation at our school, but we, the science faculty and museum staff at MJC had other plans.

More than a decade ago, the people of our county had a marvelous vision of the future, and passed Measure E, a bond issue for almost a billion dollars that would be used to modernize the antiquated buildings at Modesto Junior College. Around $80 million was used to construct the Science Community Center, a gigantic boon to science teaching in our region that includes a planetarium, a research-level observatory, a natural history museum (the Great Valley Museum), and the labs and classrooms for our courses in biology, physics, chemistry, astronomy, and the earth sciences. It is now one of the finest teaching facilities in the state, but it wasn't finished.

For more than three decades the science faculty and museum staff have been trying to put together an outdoor nature laboratory that would complement the science labs and museum experience. Over and over the proposals were made, and time after time we were told there was no budget available to complete such a project. With the passage of Measure E, it looked like the dream might actually come to fruition. But it wasn't an easy road. There were many proposals, and one by one the highest priority projects were constructed. The pool of available funds dwindled to the last few million dollars, and there were still another dozen or so proposals competing for the last of the funds. We went through several presidents during that time, and some supported our proposal and some didn't. The possibility of ever getting an outdoor education laboratory seemed to be dwindling.

But finally word came out that the project had been approved! The planning process then needed to start, and I served on the committee that designed the lab. We came up with what we thought would be the best blueprint, and it went out to bid. The bids came in high, so we went back to work with a modified proposal. I may have missed a memo, because a bid was finally accepted and when I walked into my office this morning a construction crew was beginning to bulldoze and survey the field! It's an exciting moment for our community.
When it is completed, this empty field will have a greenhouse and a collection of native vegetation of the Great Valley and the surrounding foothills. There will be outcrops of the important rocks of the Sierra Nevada foothills, including granite, the "tombstone rocks" of Mother Lode slate, the volcanic rocks of Table Mountain, and others. There will be a vernal pool, a biological oddity that is practically unique to the Great Valley. There will also be a simulated paleontology excavation pit that will allow school children to experience what it is like to dig for the fossils that have been found in our region. The children who visit our Great Valley Museum will have the opportunity to see exhibits about the natural history of the region, and then they will be able to go outdoors and experience the natural environment directly. Our long-term dream is finally becoming a reality.

Wow, that was fast. I finished my morning classes and look out over the work area and the perimeter fencing is already up.
 And after my lunch, there's a bulldozer already scraping off the surface weeds. Fast moving!