A California Love Letter: It's the Best Geology to be Found Anywhere!

This is the second of some resource materials I have on our college website that are being removed, so I wanted to preserve them. The following is some info I give to my students of my "Geology of California" course. For the majority of these students, it is their first introduction to geology, and their first introduction to the extraordinary state that is their home. For a more complete explanation of each superlative, click on the orange links (down the rabbit hole!). Enjoy!

Highest point in the lower 48 states: Mt. Whitney, 14,505 feet 

Lowest point in the western hemisphere: near Badwater, Death Valley, -282 feet

The deepest canyon in North America (maybe): Kings Canyon, Giant Sequoia National Monument. Hells Canyon on the Oregon/Idaho border may be 19 feet deeper. Maybe...

Largest living things in the world: Sequoia Trees

Tallest living things in the world: Coast Redwoods

Oldest living things in the world: Bristlecone Pines (5,000 years), White Mtns, or Creosote Bushes in Colorado Desert (11,000 years)

My Scottish BBC Interview at a relatively balmy 110 degrees

Hottest Place on the Planet and Driest Place in North America: Death Valley: 134 degrees, precipitation 1.4"/year

One of the Snowiest Places in the U.S.: Tamarack, Sierra Nevada, 76 feet in one year, 32 feet in one month, 37 feet on ground at one time

Highest Waterfall in the North America (no. 7 in world): Yosemite Falls, 2,425 feet

Second tallest active volcano in the U.S.: Mt. Shasta, 14,162 feet

Second most recently active volcano in lower 48 states: Mt. Lassen (1914-21)

Most voluminous volcano in the lower 48 states: Medicine Lake Highland (around 130 cubic miles) in northeastern California

Scarp from the 1872 Lone Pine earthquake

Some of the largest earthquakes in the lower 48 states: 1906 (San Francisco 7.8), 1872 Lone Pine (7.8), 1857 (Ft. Tejon 7.8)

Old oil derrick near the Santa Clarita Valley

One of the more prolific oil and natural gas producing regions in the world: Los Angeles Basin, Bakersfield, and Santa Barbara-Ventura Channel

One of the biggest explosions ever: Long Valley Caldera, 750,000 years ago, 125 cubic miles of ash spread all over the western states as far east as Nebraska and Kansas

McWay Falls at Julia Pfeiffer-Burns State Park on the Big Sur Coast

No other state has the combination of landscapes: Coastlines, deserts, mountains, river valleys and plateaus, due in no small part to the fact that California is influenced by all three different kinds of plate margins: Divergent, convergent and transform. Few places in the world have this kind of diversity.

The San Andreas fault on the San Francisco Peninsula. San Andreas reservoir, from which the fault took its name, is in the foreground.

What would you add to this list???

The San Juan Bautista Earthquakes as recorded at Modesto Junior College

We have a simple classroom seismometer installed on the third floor of our Science Community Center at Modesto Junior College. It nicely captured the two earthquakes from San Juan Bautista that took place last night just five minutes apart. In the record above you can see the 3.6 magnitude foreshock on the left side, and the larger 4.2 magnitude quake in the center. This seismogram nicely illustrates the vast difference in the size of the two quakes. In terms of energy release, a magnitude 4 quake is about 32 times more powerful than a magnitude 3. So the 4.2 quake is many times larger than the 3.6 (can a seismologist out there do the calculation?), which is obvious from the graph above. The 4.2 was not just a little bit bigger, it was huge in comparison.

I isolated the magnitude 4.2 and "stretched" it out. One can see from the horizontal scale that the vibrations continued for two or three minutes at our location. The quake would have been a few quick jolts near the epicenter, but the unit is far more sensitive than humans are. The really big quakes can  reverberate for hours.

The unit is an EQ-1 Seismometer from Next Generation Science. It uses a suspended magnet in near contact with an electronic coil. Vibrations are recorded electronically and converted to digital signals on the computer which can be manipulated to bring out details of the individual quakes. In the few months I've had it installed, I've recorded California quakes in the range of magnitude 3.5-6.0 (the Napa quake). It has also captured magnitude 7 and larger events worldwide.

The unit shouldn't really be on the third floor of the building, because it catches all manner of foot traffic, trains and traffic. On the other hand, what a great teaching tool. I've used a signal splitter to put a second monitor in the window with some interpretive notes. I've had any number of people who've stopped by to jump up and down, creating their own little earthquakes (about magnitude -2, I understand).

Magnitude 6.5 Quake Offshore of Northern California

A magnitude 6.5 quake has struck offshore of northern California, about 25 miles offshore of Ferndale and Eureka, at 4:27 PST. It was apparently felt widely across the northern part of the state. Seven aftershocks in the range of 30-4.5 magnitude have followed the main shock so far. This area is quite close to the Triple Junction where three plates, the Gorda, Pacific and North American come together. The fault motions were primarily horizontal so a tsunami is not considered likely (and it would have hit onshore by now anyway). Andrew Alden at About.com:Geology provides a nice perspective of the quake, the biggest in the lower 48 states in a couple of years.

Update, 1/10: 23 aftershocks thus far, including three that exceeded magnitude 4. Some minor damage reports, in the form of fallen chimneys and broken windows. A nice history of seismicity in the region by the Berkeley Seismological Laboratory can be seen here.

A Volcano Sundered: A Field Trip Along the San Andreas Fault IV

One of California's hidden treasures is Pinnacles National Monument, in the Coast Ranges south of the town of Hollister. It was the main destination of our field studies class last week as we explored sites along the San Andreas fault. Some of our other stops were described here, here and here. The park was established by Theodore Roosevelt in 1908, to preserve the unusually rugged scenery that is quite unlike that of most other parts of the Coast Ranges. The surprising geological significance of the park was not discovered until a half a century later.

I described the geology of the park in some detail last year, so I won't repeat myself too much, but essentially the park is half of a rhyolitic composite volcano that erupted 23.5 million years ago...right on top of the San Andreas fault! The rhyolite weathers into the beautiful spires and peaks that are the centerpiece of the park scenery.

In the 1970's, geologists were looking to understand the nature of movements along the San Andreas fault, and some of them noted the apparent similarity between the Pinnacles volcanic rocks and those of the Neenach Volcanics down in southern California near Palmdale and Gorman. V. Matthews was able to demonstrate that they erupted from the same volcano, but that the rocks were separated by 195 miles by movements of the San Andreas fault. The discovery was a powerful confirmation of the possibility of large-scale motion of the crust of the earth.

Because of the crap going around today about the end of the world and 2012 movies, I feel duty-bound to point out that this 195 miles of movement was accomplished by thousands of individual earthquakes happening once every few hundred years, with 10-20 feet of motion during each earthquake. Such earthquakes are likely in the near future, and they will be disasters, but they will not be anything like what goes on in Roland Emmerich's imagination, as entertaining as his movies may be!

Some classic papers:

Hill, M.L. and Dibblee, T.W. Jr., 1953, San Andreas, Garlock, and Big Pine faults, California - A Study of the character, history and tectonic significance of their displacements: Geological Society of America Bulletin, volume 64, pp. 443-458.

Matthews, V., 1976, Correlation of Pinnacles and Neenach volcanic formations and their bearing on San Andreas Fault problems AAPG Bulletin 60: 2128-2141

Large Quakes in Gulf of California

Some large quakes within the Gulf of California a short time ago, with the largest preliminary magnitude at 6.9. They all happened within a few minutes of each other, so I expect the reported magnitudes will change as they sort out the data. The closest town is Santa Isabel in Baja California, 76 miles away. A 5.8 shock preceded the 6.9 event, which was followed by aftershocks at 6.0 and 5.0 magnitude.

The Gulf of California is the result of divergence, where Baja is sliding northwest and separating from the Mexican mainland. The movement of Baja is intimately related to motion on the San Andreas fault in California, as Baja and all the lands in Alta California west of the San Andreas are part of the Pacific Plate, which is shifting northwest at around 2 inches a year.

It's a good reminder that California is earthquake country, and that enough stress has built up on different sections of the San Andreas fault to produce major quakes. You can read lots more about earthquake hazards at http://earthquake.usgs.gov/.

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.

The Accretionary Wedge Carnival!

The Accretionary Wedge carnival is a monthly forum amongst geobloggers highlighting some of our favorite gripes, pleasures and intuitions. It is entertaining to see how our colleagues and associates think! This month's theme, hosted by Green Gabbro (http://greengabbro.net/) is your (least) favorite misconceptions in geology, and an alternate choice, pies and geology (in honor of national pie day on January 22). Here is my submission...check it out and add your own!

Every semester I start a section on earthquakes with my students offering their assumptions and misconceptions about earthquakes. Some of the most popular:
1. California will fall into the sea
2. California has the largest earthquakes in the world
3. California has the most earthquakes of anywhere in the world
4. The ground opens up and swallows people
5. Psychics predict earthquakes
6. Animals predict earthquakes
7. We are waiting for THE BIG ONE!
8. The safest place in an earthquake is a doorway
9. All California quakes happen on the San Andreas fault
Since there is at least a (very) small element of truth in a (very) few of some of these, it leads to a good discussion on earthquakes.