Airliner Chronicles: Finding Fault by Flying

Flying can be no fun whatsoever, what with the lines, the waits, the security checks, surly attendants, and the tarmac delays. It would be intolerable were it not for window seats. So while I'm in connecting flight limbo, here is a sight from my flight between Oakland and LAX today. We generally flew right over the San Andreas fault for most of the flight, but in Southern California, the fault takes a more southeasterly trend and it suddenly appeared below me. This section of the San Andreas is just west of Gorman at the summit of the Grapevine, the point where Interstate 5 crosses the Transverse Ranges on the way into Los Angeles.

The "Airliner Chronicles" is a throwback to the very first blog series I did way back when. I don't fly all that often, but if there is good geology below, you can be sure that I'm trying to capture it in pictures.

The Antelope Valley California Poppy Reserve: Color in the Western Mojave Desert This Week

I admit I've taken artistic license, in that I took this picture of a busy hummingbird on the same day, but by the time I took the shot, I was two hundred miles north in the parking lot of a Black Bear Diner in Tulare, California on my way home. But it sure catches the eye, doesn't it?

We were in Southern California for the wedding of my god-daughter this last weekend (have a great life Megan and Richard!), and I must say they picked a good time to give us an excuse for hitting the road. On the way home we made our way along the San Andreas fault from Cajon Pass to the Grapevine, hunting for earthquakes, and hoping to see some colorful wildflowers, despite California's crippling drought. A drought, yes, and a huge water deficit, but we had a few good storms roll through the state in the last few weeks, giving a boost to the wildflower season.

We took a chance and headed out the Antelope Valley California Poppy Reserve to see if the poppies were blooming. They were. They are certainly a bit more limited in scope than in wetter years, but they formed a beautiful golden carpet across the desert floor. They were also mostly closed up in the fierce wind that was blowing through the area in the aftermath of the storm. The poppies are natural, but exist here for an unnatural reason, a topic I discussed back in 2010 in this post.

In that post I described how.the flowers are a natural phenomena, but a natural phenomena with a very human influence. About seven miles west of the Poppy preserve there is another state park: Arthur B. Ripley Desert Woodland State Park. The park preserves 580 acres of what turns out to be the native land cover of the Mojave Desert west of Lancaster and Palmdale: juniper woodland and Joshua Trees.

A century ago, this high end of the desert was cleared of Joshua Trees and Juniper, usually by chaining (dragging a huge chain between tractors that knocked down whole forests) or fires in order to put in thousands of acres of alfalfa fields and other crops. Large areas were reserved for sheep and cattle grazing as well. The natural plant cover was long gone. Much later, some of the abandoned fields started to recover, and the showy wildflowers are the pioneer species that are the first to recolonize disturbed lands.  Joshua Trees can no longer recolonize the valley floor; they don't have any method to spread their seeds widely (Joshua Trees were once spread in giant ground sloth poop...). Despite their incredible beauty, the wildflower displays are a monument to our extensive alteration of the environment that once existed here.

Many of the agricultural fields have been abandoned for lack of water and other economic reasons, but our utilization of the desert for our human needs continues. Notice in the picture below the huge windmills in the distance, and what I think is a large solar array.

After taking in the beautiful fields of California Poppies, we headed west along the San Andreas fault to Highway 138 and the Gorman cutoff. Suddenly the hills were alive again with what looked like the beginning of a nice blooming of lupines and some kind of yellow flower (we didn't have time to stop and investigate closely).

I imagine that in a week or so this will be a true wonderland of color, especially after the weekend dousing by the short but intense storm that rolled through California. The storm was too late to do anything about the drought, but it brightened the world just a little before the summer heat sets in.

The Other California: The Volcanic Mountains of the City of Angels

Volcanic mountains in Los Angeles???

Well, sure there are. Of course we need to define what is meant by "volcanic mountains". If you are imagining a chain of active volcanoes spewing out lava flows down Wilshire Boulevard, well, no there aren't any of those, despite what you might have seen in a Tommy Lee Jones movie a few years back.

Extinct volcanoes, maybe? No, I'm not really aware of any of those in the L.A. region either. I've never noticed any suspiciously conical hills in the metropolitan area in my travels that way. If you want to see a city that will probably be the setting for a great disaster movie (but not a very pleasant event if it were to happen for real), you might try a place like Auckland on the North Island of New Zealand. That particular city is built on four dozen volcanoes, including some that erupted only 600 years ago (below).

Yup, if you are a Kiwi, you can latch onto a 'hot' property here.

But there are volcanic mountains adjacent to Los Angeles. They just aren't actual volcanoes, as the original vents have long since been eroded away. The city is practically surrounded by exposures of volcanic rocks. There are some on the Palos Verdes Peninsula, in the mountains above Orange County, and in the hills near Glendora and Pomona. Perhaps the best place to see volcanic rocks near LA though, is the Santa Monica Mountains and their offshore extension, the Channel Islands.

I am guilty of ignoring the Santa Monica Mountains. I grew up in Southern California and never knew of them being much more than those hills up behind Malibu, and a place where I once attended the Renaissance Faire. I spent my available weekends up in the high country of the San Gabriels, the San Bernardinos, or the Sierra Nevada. This last summer I found that I was missing out on an extremely interesting and diverse mountain range. It has a geology professor's dream of intriguing rock exposures: metamorphic, plutonic, sedimentary, and as the post title suggests, volcanic rocks.

The volcanic sequence is not of a familiar origin. The so-called Conejo Volcanics were mostly extruded on the seafloor, only occasionally rising above the waves as islands. Volcanic activity is usually associated with divergent or convergent plate boundaries. The Conejo lavas were not exactly associated with either situation.

At divergent boundaries, the oceanic crust is pulled apart, releasing pressure on the underlying asthenosphere, a hot layer that is close to the melting point of the olivine-rich rocks of the mantle. The decompression allows a small portion of the asthenosphere to melt, producing basaltic lavas. At convergent boundaries oceanic crust is driven into the mantle underneath the adjacent oceanic or continental crust. As the rocks sink into the hotter asthenosphere, the added oceanic water acts as a catalyst or flux, lowering the melting point of the surrounding rocks. Bodies of magma called plutons rise through the crust forming volcanic arcs like the Andes, the Cascades or the Aleutian Islands.

Hey, the Santa Monica Mountains don't look like this at all...

A few other volcanic systems aren't related to plate boundaries. Thermal plumes, or hot spots, are responsible for sequential series of volcanoes on the sea floor (Hawaiian Islands) or on continents (Yellowstone caldera).

For most of the last 30 million years Southern California has been dominated by the lateral motions of the San Andreas fault system, a transform plate boundary. The fault system has not been a simple line, and the position of what we call the San Andreas fault has shifted about a number of times. One of the biggest changes was a shift eastward as the Gulf of California opened up around 4 or 5 million years ago. Transform boundaries are not normally associated with volcanic activity, but there are definite exceptions, and that seems to be the case in the area that is now exposed as the Santa Monica Mountains and Channel Islands.

The Santa Monica Mountains are part of the California province called the Transverse Ranges. They are one of only two mountain ranges in North America that are oriented east-west instead of the usual northerly trend (the High Uintas of Utah are the other). The discovery and acceptance of plate tectonics provided an elegant explanation for the origin of most of the world's mountain ranges like the Alps, the Himalaya and the Andes. The acceptance of the theory seemed to deepen the mystery of the origin of the Transverse Ranges. How could a northwest trending transform boundary produce an east-west trending set of mountains? Or did these mountains have anything to do with the transform faulting at all? Some researchers suggested the structure of the Transverse Ranges predated the onset of transform faulting. The Transverse Ranges are a treasure trove of ongoing and potential future research in structural geology and landscape evolution.

Tanya Atwater and the Educational Multimedia Visualization Center at U.C. Santa Barbara have provided us a marvelous animation that offers an excellent explanation for the onset of volcanism in the ranges around 13-16 million years ago (there are many excellent animations available for free download on the site).

As you watch the video unfold, you will see that the crustal blocks that constitute the Transverse Ranges have been literally rotated 90 degrees or more, having been caught between strands of the fault system. As the blocks rotated, extensional forces caused openings in the crust, forming deep sedimentary basins that collected thousands of feet of sediment, and also allowing magma to rise from the mantle forming volcanoes on the seafloor,  These are the rocks that make up much of the Santa Monica Mountains.

This animation is courtesy of the Education Multimedia Visualization Center.

Download this and many others at this site.

These volcanic rocks formed more than ten million years ago. Tectonic conditions have shifted and much of the region is now under the influence of compressional forces that are much less likely to result in volcanic activity. But it makes for a chaotic mess of earthquake activity as events like the 1994 Northridge earthquake can attest.

The Santa Monica Mountains are a confusing patchwork of federal, state, county, and city parklands and include large areas of private property. Land use ranges from densely urbanized areas (the mountains include parts of Hollywood and Beverly Hills ) to untrammeled wilderness. A good place to start planning your exploration is the website for the Santa Monica Mountains National Recreation Area. A look at the park map reveals the logistical headache of trying to administer the parklands.

The Other California is my ongoing exploration of the less-known geological corners of our beautiful state. Tens of millions of people visit the California Coast every year, and on one Labor Day weekend something like 800,000 people may hit the beaches at Malibu. In a year less than 500,000 will visit parks like Malibu Canyon or all of the federal units combined. The interior parks are great places to escape the crowds.

In the next post, we'll take a look at an unexpected canyon in the Santa Monica Mountains, and what does Korea have to do with anything?

The Other California Compilation Updated

I posted several entries in my long-running blog series on the "Other California" and realized that I was linking to a compilation page that was woefully out of date. I went through and added more than two dozen entries that I posted over the last two years, including a lot of material for the Sierra Nevada, the Transverse Ranges, and the Coast Ranges. If you are curious about some of areas I covered in the past, check out the compilation on the Other California on this page.

Registration Deadline Extended: Far Western Section NAGT Meeting

(Cross-posted from Teaching the Earth Sciences)

The registration deadline for the Spring 2011 NAGT conference (see previous post), to be held at Caltech in Pasadena, CA, on March 25 - 27, has been extended to March 11. The registration fee is $95 for all payment postmarked by March 11. For payment postmarked after March 11, the fee will be $125. Go to the conference web site at

http://www.tectonics.caltech.edu/meetings/nagt/index.html

Students of the geological sciences are invited and encouraged to attend Far Western Section events at greatly reduced rates. See the conference website for details. Hope to see you there!

Far Western Section, National Association of Geoscience Teachers Spring Meeting: Caltech Tectonics Observatory, March 25-27, 2011

(Cross-posted from Teaching the Earth Sciences)
Have you ever wanted to know more about the geology of southern California, the San Andreas fault, and some of the incredibly strange rocks that crop out around the San Gabriel Mountains, like Vasquez Rocks or Devil's Punchbowl? The Far Western Section of the National Association of Geoscience Teachers invites you to join us on March 25-27, 2011 for our spring meeting, hosted by the Caltech Tectonics Observatory in Pasadena, California. These meetings are a great way to learn some fascinating geology, meet some fascinating people, and as much as I would like to say "have a scholarly time", I'm going to instead say "have a fun time".

Complete details of the meeting can be found on the Caltech Tectonics Observatory website at http://www.tectonics.caltech.edu/meetings/nagt/. You do not need to be a member of NAGT to attend (but we will gladly welcome you into membership if you wish to!), and the cost of the event is modest (less than $100 if you register before Feb. 25, plus a bit more for the Saturday banquet).

Check out the wonderful slate of activities and field trips below!

Field trips:
•Erosion and Sediment Transport in steep Mountain Terrain, San Gabriel Mountains - Mike Lamb (Caltech)

•San Gabriel Anorthosite and the San Andreas Fault - Bruce Carter (Pasadena Community College)

•Vasquez Rocks - Elisabeth Nadin (UA, Fairbanks) and Rebecca Walker (Mt San Antonio College)

•Devil's Punchbowl and Red Rock Canyon - Donald Prothero (Caltech/Occidental College)

Evening Speakers:
•Good Vibrations Inside the Earth - Jennifer Jackson (Caltech)

•TBD -Jess Adkins (Caltech)

Exhibits and tours:
•Tour of Seismo Lab - Margaret Vinci (Caltech)

•Southern CA Earthquake Center (SCEC) display

Workshops:
•Low-T Thermometry and Thermochronometry and Applications (including dating the formation of the Grand Canyon) - Ken Farley, John Eiler, and Brian Wernicke (Caltech)

•Earthquake Magnitude, Energy, and Focal Mechanisms (beach balls) - Joann Stock (Caltech)

•Plate Tectonic Rotation of the Transverse Ranges: what happened, how we know it happened, and how it created Southern California’s unique geography, climate, ocean currents and biological richness - Tanya Atwater (UCSB)

•Historical Earthquakes and Uplift/Subsidence of Sumatra from Coral Growth Rings - Elizabeth Nadin (UA, Fairbanks) and Belle Philibosian (Caltech)

•Operations of Community Seismometer Network (How your laptop can help scientists better understand earthquakes) - Tom Heaton and Ming-Hei Cheng (Caltech)

The registration form is here: http://www.tectonics.caltech.edu/meetings/nagt/register.pdf. Join us!

Learn more about the activities and opportunities at the Far Western Section! Check out our website, the Far Western Section of the National Association of Geoscience Teachers here, the FWS blog here, and our Facebook page here.