Register for the Fall Meeting of the National Association of Geoscience Teachers! Oct. 10-12 at CSU Sacramento

The 2003 meeting sponsored by CSU Sacramento: Exploring the Malakoff Diggings

The fall meeting of the Far Western Section of the National Association of Geoscience Teachers is taking place on Oct 10th-12th in Sacramento at California State University Sacramento. Trip opportunities include the Sierras, Delta and local Sacramento geology.  Professors, K-12 teachers, and students (official and unofficial) of the earth sciences or geology are encouraged to join us. You do not have to be a member of the NAGT to attend, although we would love to have you join our organization. We encourage and support the teaching of the earth sciences in California, Nevada and Hawaii, and try to sponsor meetings that are not a great stress on teachers and students on limited budgets. You do not have to live in these three states either. These meetings are a great way to become acquainted with the geology of this fascinating region!

Here is a sampling of some of the exciting field trips that are planned:

1.    A Traverse of the Sierra Nevada from Sacramento to Donner Summit-Eldridge Moores, Emeritus Professor, Geology Department, UC, Davis  

2.    Bay Delta Hydrology and Geology-Rob Barry, Chief Project Geology Section, California Department of Water Resources; John Suen, Professor Emeritus, California State Univ., Fresno; Mark Pagenkopp, Geologist, Calif. Dept. of Water Resources

3.    Gold, Aggregates, and the Yuba Dredge Fields, California Mineral Education Foundation, Cynthia Pridmore, Engineering Geologist, California Geologic Survey

4.    Miocene, Pliocene, and Pleistocene Stratigraphy near Sacramento, CA. Tim Horner, Chair CSU, Sacramento, Geology Department, CSU, Sacramento

5.    The Legacy and Effects of Mercury in California Gold Rush Streams -Mike Hunerlach, Regional Mining Geologist and Liaison US Forest Service, Charlie Alpers, Research Chemist, United States Geologic Survey. 

Speakers:
Stephen Testa, California State Mining Board-Oil, Gold, Earthquakes and Higher Education in the latter half of the 19^th Century.

Sue McClurg, Deputy Executive Director, Water Education Foundation The Bay Delta Conservation Plan: How did we get here, and where are we going? 

Lots of other activities and field trips are scheduled!

Register now! Information can be found at the links below:
    Register Online, using credit card or PayPal! http://nagt-farwestern2014.bpt.me/ 
    Registration form: http://nagt-fws.org/New_Registration_Form-1.pdf
    Conference Information: http://nagt-fws.org/NAGT_fall_conference_info.docx.pdf
    Conference Agenda: http://nagt-fws.org/NAGT_FWS_2014_Conference_Agenda.pdf
    Accommodation Options: hhttp://nagt-fws.org/Accommodation_Options_Fall_2014.pdf

Hydraulic mine in the California goldfields.

The Airliner Chronicles: Three Faces of California's Great Valley

According to this interesting article from the New York Times, it's larger than 9 American states. It is the largest patch of Class 1 Soil in the world (i.e., the best for agriculture). More than 230 kinds of crops and produce are grown there, and the output represents 8% of the nation's agricultural output (on 1% of the land). Around 6.8 million people live there, and the average per capita income is lower than most of the rest of the country (it has three of the five poorest cities), and unemployment is far higher. It is California's Great Valley, my home.

From http://en.wikipedia.org/wiki/File:Map_california_central_valley.jpg

The valley is 400 miles long, 30-50 miles wide, and is almost entirely flat (except for the Sutter Buttes, the highest elevations are 400 feet or less). It is drained by several major rivers, including the Feather and Sacramento Rivers to the north, and the San Joaquin, Kings and Kern Rivers to the south. Although most of the rivers leave the valley through the Sacramento Delta into San Francisco Bay, those in the south do not. They once ended in huge lakes like Tulare and Buena Vista, but today the lakes are long gone, having been dried up by agricultural diversions upstream.

I've long heard that only 5% of the valley remains in the natural state that existed prior to agricultural development, and from the air, this is obvious. All the times I've flown over it, I have been struck by the continuous patchwork of plowed fields (it clearly resembles the kinds of blankets my grandmother used to make out of the leftover fabric squares). There are a few tracts of undeveloped grasslands off to the south, but for the most part only the rivers retain much of their original vegetation, but only in a few places.

Today's photos come from three distinctly different parts of the valley's river systems. In the colorful top photo, we can see a portion of the Sacramento Delta, where the San Joaquin and Sacramento Rivers come together in a maze of islands that have been mostly converted to farmlands. The islands are protected (somewhat) from seasonal floods by a series of poorly constructed levees that are subject to destruction from even moderate earthquakes. This has set up what potentially could end up as California's worst possible natural disaster (at least in the monetary sense). The islands have been sinking due to groundwater withdrawal, soil loss, and oxidation of organic material in the soils. Most of them are now below sea level, with only the vulnerable levees keeping them from being flooded. Since the intake pumps for the California Water Project lie in the midst of these islands, broken levees will draw salt water into the delta, where the domestic water supply for most of the southern state is tapped. An earthquake has the capability to disrupt the state water system for several years.

The north end of the Great Valley is drained by the Sacramento River which can be seen in the photo above, taken near Colusa. The landscape has been completely co-opted by agricultural fields, right up to river's edge. It looks like the river has been "conquered" and tamed by the works of humankind, but floods like those of 1997 and especially of 1861-62 could leave just about the entire area in the photo above under 10-20 feet of water (see my take on these ARkstorms here).

The San Joaquin River drainage contains some of last remaining natural grasslands and riparian landscapes in the Great Valley. The structure of the valley is that of a series of shallow basins separated by the alluvial fan systems formed by the Merced and San Joaquin Rivers. The basins have essentially caused the river to back up and develop wide floodplains where the streams meandered widely, changing channels in unpredictable ways. The area in the picture above is just north of the town of Los Banos, an area of abandoned meanders, bogs and swamps protected as the San Luis National Wildlife Refuge and Great Valley Grasslands State Park. The land is not entirely unaffected...decreased flows caused by reservoirs and diversions upstream have caused many of the swampy areas to dry up. Efforts (and negotiations) are ongoing to increase river flows in a hope of rebuilding the disrupted ecosystems, especially those of the salmon which used to be common in these waters.

The Airliner Chronicles is one of my on-again/off-again serial features, which is usually updated whenever I fly somewhere.

The Airliner Chronicles: California's Coming Katrina Moment

What is the biggest geologic hazard facing the California? We have famously had disasters caused by earthquakes, floods, wildfires, and dam failures. But at least we don't have to worry about a Katrina-style disaster, of losing an entire city to floods brought on by levee failure during a major hurricane. Or do we?

Welcome to the Sacramento Delta. The Sacramento and San Joaquin Rivers drain most of the Sierra Nevada and Central Valley, and represent 50% of the available water resources in the state. The Delta is practically unique in the world. Most deltas extend out to the sea, like the Nile or Mississippi, but the Sacramento is far inland. This is a consequence of sea level rise following the end of the last ice age, and the arrangement of structural blocks that compose the Coast Ranges, which forces the vast drainage through a single channel at the Carquinez Straits. The Sacramento and other rivers break up into a series of sloughs and channels that define around 60 "islands". These islands were once rather ephemeral, changing as a result of yearly floods and runoff events. When the agricultural potential of the islands was recognized in the 1800's, they were surrounded and outlined by a series of levees to stop the seasonal flooding. Ultimately an area of 1,150 square miles came under the plow.

The law of unintended consequences was certainly in effect here. The peat-rich soils were originally anaerobic marshes, and buried carbon stayed buried. Once farming began, the groundwater was not constantly being recharged, the drier soils began to oxidize, and the land began to subside at a rate of an inch or two every year. Today the majority of the islands are below sea level, in many cases by as much as 10 to 25 feet. The levees prevent flooding by holding back the rivers and sloughs on a year-round basis. It is quite interesting to drive across the delta, and climb uphill in order to cross the rivers and channels!

The construction of the levees had another effect that is essentially a positive, but is also a problem. The delta is subject to tidal changes, and saltwater intrudes into the delta during high tides and droughts. Prior to levee construction, the saltwater intruded many miles further into the delta, but in recent decades the intrusion has been far less (this is also an effect of water releases from dams far upstream).

Which leads us to California's huge vulnerability: what happens if the 1800's-vintage levees fail? We have a pretty good idea because it happens on a much too regular basis, more than 100 times since 1890. Major flood events like the 1997 disaster caused levee failures in several places. Some failures have been caused by trivial things like muskrat burrowings. Singular events such as these have flooded thousands of acres. But what would happen if dozens of the islands were flooded all at once? Unthinkable? Unfortunately a very real possibility. It's all about earthquakes.

The saturated earthen levees are subject to liquefaction, where a loss of cohesion of the soil results from the breakdown of the surface tension of the water that was holding the grains together. Think of it this way. A sand castle holds its shape in damp sand, but loses it if too much water is added. If you stomp on wet sand at the beach, it will liquefy, and you will sink a few inches. The same thing can happen on a large scale with a levee, and thus earthquakes stand as one of the most greatest threats to the integrity of the levee system. And the system has not been truly tested: many of the levees hadn't yet been finished in 1906, and the 1989 Loma Prieta quake (magnitude 6.9) was too distant from the delta to have much of an effect. But a number of active faults pass through or near to the delta, and it won't require a "BIG ONE" to do the damage. A 6.0-6.5 near by on one of these faults will be more than enough.

If widespread levee failure takes place, dozens of islands will be flooded with saltwater, and the thousands of acres of prime agricultural lands will be lost. To be sure, thousands of people live on these tracts, and they will be homeless, perhaps permanently (is it really worth it to reclaim an island that is 25 feet deep in salt water?). But this isn't the biggest problem. It's that fact that 23 million people, most of the population of the state, are depending on delta water for their domestic and agricultural use.

The California Water Project and other systems pump water out of the delta for use by cities and farms off to the south. In the event of a worst-case scenario earthquake, the pumps will be fouled by salt water for months or even years. The state's single largest source of fresh water will be gone. It's a huge problem that until recently was not receiving attention, but apparently that has changed, and the legislature and governor are catching up to the pleas of the water managers about the huge vulnerability of our water systems.

There are great many other issues with the use of water in California, of which the problems of the delta are only a part: a rather extensive review can be found here. Droughts, climate change, ecosystem deterioration, and water waste are all serious problems that have to be dealt with pretty much immediately. But preventing a Katrina-style levee failure has to be near the top of the list. It could literally happen tomorrow...

I snapped today's picture if the Sacramento Delta on a flight out of San Francisco in 2006.

Shaking in my Boots (er, my Keen's)

It's been kind of "late in the semester" busy, so blog posts have been limited, but it doesn't mean that nothing interesting is happening in the world. Volcanoes in Alaska (how's that "something called volcano monitoring" working out for you Gov. Jindal?), and now earthquakes in California. Nothing that is totally out of the ordinary, but enough to pay attention to.

It started a few days ago down in the Salton Sea area where the San Andreas fault stops. It just ends down in the sand and gravel beneath the Imperial Valley. What actually happens is that the zone of fault movement skips to the west a bit, and an area of stretching resulted in the formation of the deep fault valley (or graben) where we grow our winter crops around Brawley and Calexico. The quakes ranged as high as magnitude 4.8, and there have been 300-400 quakes in the immediate vicinity. The swarm has seismologists a bit concerned, as this is a part of the San Andreas fault that has not produced a major earthquake (7.5+ magnitude) in hundreds of years. They consider that this swarm has a 1-5% chance of being a foreshock to a major event.

The San Andreas is a complicated piece of work. It slices across California, through Thousand Palms, San Bernardino, Palmdale, the central Coast Ranges, Santa Cruz, Daly City, and Mendocino, and despite what the ridiculous TV movies tell you, we aren't going to fall into the sea. At least, not yet. Wait around for 20-30 million years, and Baja may be an island out in the Pacific. The land is moving northwest an average of 2 inches per year, but the actual motion is more like 10-20 feet during earthquakes every century or two.

Our big earthquakes occur on three discrete areas of the fault, in the north from San Juan Bautista to Mendocino (site of the 1906 event), from Parkfield to Cajon Pass (site of an equally large ~7.8 event in 1857), and from Cajon Pass to Salton Sea (an area that has not had a big event in maybe 300 years). Some overlap occurs sometimes, especially around Cajon Pass. An area from Parkfield to San Juan Bautista creeps a little bit every year without producing major quakes. And Parkfield has magnitude 6 quakes roughly every 23 years or so, although the last one (in 2004) came about 18 years late. Each major section of the fault has an average recurrence interval of around 150 years, but events cluster a bit with time gaps of 90 to 300 years (and I will gladly correct these numbers; they're a few years old and lots of research continues).

You may have heard of the great Shakeout earthquake drill that took place a few months ago in Southern California. They did it for a reason. Large earthquakes ARE coming, SOMEDAY, and if you choose to live in California you need to be ready. When one takes place, the power and water are going to be out, maybe for days or weeks. Make sure you have emergency supplies of water, food, and batteries. Know what to do during the quake; where to take shelter, how to do basic first aid, how to help others. Have a plan for contacting other family members, as local telephone service will be disrupted. Save the phones for 911 calls. Make a person outside the region a point of contact if you are separated from other family members and can't contact them directly.

It happens that I live in Northern California, where the San Andreas fault is considered slightly less of a threat for no good reason other than that it has been less time since it last rumbled. But lest I become complacent, there was a 4+ magnitude quake near San Jose this morning, near where a 5.6 quake hit last year, on the Hayward fault. The Hayward/Calaveras fault system is sort of a wild card in the earthquake game, less well-known, but capable of much mayhem. There was a "Great San Francisco Quake" years before the "Great San Francisco Quake" of 1906. It was in 1868, and occurred on the Hayward fault, killing two dozen people. Seismologists fear a large quake on the Hayward almost more than the San Andreas, as it passes through a more populated region, and will have more of a direct effect on the levees of the Sacramento Delta.

Oh, yes. The Delta. Hundreds of fatalities will be bad enough, but one of the greatest vulnerabilities in California is the system of century-old levees that keep the three dozen islands of the delta from flooding. They are below sea level today because of soil loss from winds, from soil compaction, and from oxidation of the organic material in the soil. Some lie 25 feet below sea level. It's not so much the flooding itself, but the fact that the flooding will be from salt water drawn out of San Francisco Bay. The California Water Project draws a massive amount of water from the delta, and if the islands flood, fresh water will be unavailable. This is the domestic water source for something like two-thirds of the state's population, and it may be cut-off for a year or more.

Make no mistake: I am not making any predictions in this post. At all. But mom, sis, dad, son, daughter, you do live next to various faults in central and southern California, so pay attention to whatever news comes out of these quakes in the next few weeks!

Quakes are a way of life in California, but in the end, I would rather live here rather than just about any place in the world. Earthquakes and faulting cause damage, it is true, but the spectacular scenery of our state is also the result of a long geologic history of fault activity. You can have your volcanoes, floods, hurricanes, tornadoes, and ice storms: I'll take the occasional quake any day!

Today's photo is a section of the San Andreas fault where it crosses I-5 at Fort Tejon at the top of the Grapevine. The fault runs up the center of the photo, and over the distant pass (the snowy flank of Frasier Mtn is on the left side). These straight valleys, eroded out of the weak rock in the fault zone are called linear valleys.