Carrizo Plain (and the San Andreas Fault), California
Posted by graywacke on March 23, 2015
First timer? In this formerly once-a-day blog (and now pretty much a once-every-three-or-four days blog), I have my computer select a random latitude and longitude that puts me somewhere in the continental United States (the lower 48). I call this “landing.” I keep track of the watersheds I land in, as well as the town I land near. I do some internet research to hopefully find something of interest about my landing location. To find out more about A Landing A Day (like who “Dan” is and what the various numbers and abbreviations mean in the first paragraph), please see “About Landing,” (and “Abbreviations” and “Cryptic Numbers”) above.
Landing number 2166; A Landing A Day blog post number 594.
Dan: Today’s landing marks the 54th straight western / midwestern landing (but at least it’s a USer). . . CA; 101/116; 4/10; 32; 150.2.
Here we go again. 54 landings in a row that haven’t touched the east! Just like my last bunch of posts, I’ll do the statistics: Each landing, I have a 0.82 chance of a western / midwestern landing. Raise that number to the 54th power (and then take the inverse) and I get one chance in 45,087 that I would not land in the east for 54 straight landings!!!
Some of my readers have no doubt concluded that my “random” latitude/longitude landings aren’t so random. My Excel landing program is incredibly simple, and totally hinges on Excel’s random number generator. I have tested it and retested it, and I can only conclude that it’s in the Landing God’s hands . . .
Anyway, here’s my regional landing map:
And my local landing map:
I’ll zoom back a little to give you a more regional sense of where I landed:
Here’s my watershed analysis:
I landed in the Cuyama River watershed (first time ever!). The Cuyama flows into the Santa Maria, and guess what? This was my first time ever landing there as well! As you can see, the Santa Maria flows into the Pacific Ocean (419th hit).
There’s a little extra along with this Google Earth (GE) space trip to California (make sure your volume control is on):
As sometimes happens, it took me a while to realize what my hook for this post would be. As per usual (after perusing my StreetAtlas landing maps which gave me no clue about the San Andreas), I was looking at GE Panoramio photos in the vicinity of my landing. When you put your cursor over a photo icon, the photo’s title pops up, like this:
So, I Googled Carrizo Plain National Monument, and quickly realized that the San Andreas Fault runs right through it (and is incredibly obvious). Here’s a Wiki photo by John Wiley showing the fault in the Carrizo Plain:
Here’s a GE shot showing how close the fault is from my landing (and by the way, this graphic and the next took some painstaking work to get them very close to accurate):
Stepping back, here’s a broader view showing the fault and my landing, but looking further north to the Carrizo Plain:
I’ll be featuring the fault soon enough, but first a little information about the National Monument. From Wiki:
The Carrizo Plain is a large enclosed grassland plain, approximately 50 miles long and up to 15 miles across. It is the largest single native grassland remaining in California. It includes Painted Rock, which is listed on the National Register of Historic Places. The San Andreas Fault lies below the plain.
First off, this is an incredibly beautiful place that I’ve never heard of, and don’t believe is much of a tourist attraction. You won’t be surprised to see some very cool photos later in this post. So what about Painted Rock? From Wiki:
Painted Rock is a smooth horseshoe-shaped marine sandstone rock formation with pictograph rock art about 250 feet across and 45 feet tall, located near Soda Lake within the Carrizo Plain National Monument. [John Wiley photo of the rock]:
The interior of the rock alcove is adorned with many pictographs created by the Chumash, Salinan and Yokuts peoples over many thousands of years. In recent times there have been many marks left by early White settlers such as one reading “Geo. Lewis 1908”, founder of Atascadero, California. Unfortunately there has also been major defacing of this site; in the 1920s the large pictogram was irreparably damaged by a shotgun blast.
The guy with the shotgun should suffer the same eternal anguish as the thoughtful intellectuals who dynamited the Buddha statues in Afghanistan . . .
Here’s a vertical shot of the rock (also by John Wiley):
As an example of the pictographs, here’s the symbol for the sun (Wiki photo by Nicely):
Before moving on to the fault, I’d like to mention my strange run on the word “carrizo.” In my December 2014 Springfield, Colorado post (landing 2138), I landed in the Carrizo Creek watershed. Then, just two landings later (my Dalhart, Texas post), I landed in a different Carrizo Creek watershed. In that post, I noted that “carrizo” is the Spanish word for “reed.”
Then, ten posts later (January 2015), I landed near Carrizozo, New Mexico. From that post, here’s what Wiki had to say about the origin of the name:
The name of the town is derived from the Spanish vernacular for reed grass (Carrizo), which grew significantly in the area and provided excellent feed for ranch cattle. The additional ‘zo’ at the end of the town name was added to indicate abundance of Carrizo grass. The town is now often referred to as ‘Zozo.
And now, not all that many posts later, I’m featuring the Carrizo Plain. And by the way, I did a search for the word Carrizo on my blog, and these four references are all there is. Imagine that. I went over 5 years and over 500 posts with no mention of Carrizo, and then boom! Like I often say, the Landing God works in mysterious ways . . .
As a geologist, I’ve always been fascinated by the San Andreas Fault. It’s a 450-mile long slash through western California (map by Geology.com; note that the Carrizo Plain is highlighted):
You can see by the black arrows that the fault moves laterally (a “transform” fault in plate tectonics speak). The average movement along the fault is a whopping (and I’m serious!) 2.5 inches/year. OK, it’s corny, but I have to do it. How long will it be until San Jose is a suburb of Los Angeles? Well, it’s about 320 miles between the two cities. 320 miles is 1,690,000 feet, which is 20,275,000 inches. Divide that by 2.5, and get about 8 million years. A blink of an eye (geologically speaking).
Getting back to the idea of a transform fault, here’s a Wiki picture (by Los688) showing typical transform faults (the red lines):
The above figure is the classic example of a transform fault, which connects displaced portions of tectonic spreading centers (where new crust is created, like the Mid-Atlantic Ridge spreading center). Transform faults are common and can be found all over the world (mostly, like those associated with the Mid-Atlantic Ridge, under water).
Google Earth (bless her heart) actually shows sea-floor topography. Here’s a GE shot with a long transform fault across the Mid-Atlantic Ridge highlighted:
And here’s an annotated close-up of the transform fault, showing 200 miles of movement:
But the San Andreas is the mother of all transform faults. And it rips across land! What’s going on?
Big picture: Prior to about 30 million years ago, a typical subduction zone was active along the entire California coast. You all know what a subduction zone is, right? It’s where oceanic crust (being driven by a spreading center) plunges below continental crust. I featured subduction zone geology in my Mt. Shasta post (type Shasta in the search box to check it out). Subduction is still going on off the northern California, Oregon and Washington coasts (causing all of the Cascade volcanoes). Here’s a graphic I used for that post (by legacy.net):
It turns out that subduction stopped and was replaced by transform movement around 25 – 30 million years ago (more about this later). It also turns out that I’ve spoken before of the now-defunct ancient subduction zone, in my fairly recent (January 2015) Carrizozo Malpais & Sierra Blanca NM post. From that post, here’s a picture of the Sierra Blanca Mountain (from the NM Museum of Natural History & Science):
And also from that post, here’s what I lifted from the town of Ruidoso website about the above mountain (this sets the stage very nicely):
The White Mountain (Sierra Blanca) Wilderness Area is situated on the erosional remnants of an ancient volcano that probably once resembled Mount Ranier in Washington state.
This ancient volcano is approximately 25 to 40 million years old. During this time period, an oceanic tectonic plate was subducting under California creating a volcanic mountain chain that extended from Colorado, through New Mexico and west Texas, and into northern Mexico. This ancient volcanic mountain chain was very similar in composition and geologic setting to the current Cascade Mountain range in the Pacific northwest. Only further inland.
About 25 million years ago, the plate boundary changed. The plates began sliding past one another rather than one going under the other. The famous San Andreas Fault was born. This birth was the death of the subduction mechanism that created the volcanic chain in New Mexico. As a result, volcanism ceased around 25 million years ago and erosion has been the dominant geological force ever since.
The volcano has seen the upper half of its cone beveled by erosion over the last 25 million years. The lower half of the volcano is what is now present and exposed in the canyons of the Sierra Blanca Wilderness.
So, once again, beginning about 25-30 million years ago, subduction ceased along most of the California coast, replaced by lateral movement along the plate boundary. My big question is why?
I spent an inordinate amount of internet time trying to get a gut-level answer to this question. No luck. The best I can do is a US Geological Survey website that purports to answer that exact question. Here’s the graphic from the article (note that the Farallon plate subducted, but the Pacific Plate didn’t):
This shows that as soon as the Pacific Plate bumped into the North American Plate, the Farallon Plate was bifurcated, and became the Cocos Plate (to the south) and the Juan de Fuca Plate to the north. The Pacific Plate never subducted (unlike the Farallon Plate), and a transform fault formed, such that the Pacific Plate began slipping to the north, rather than subducting.
Trouble is (even though the title of the article is “Evolution of the San Andreas Fault”), the author never clearly explains exactly why it is that the Pacific Plate didn’t subduct. Oh, well.
So it’s time for some fun San Andreas Fault pictures. Here’s one from Geology.com, with the caption beneath:
Photo of the San Andreas Fault near Gorman California, showing gray rocks of the Pacific Plate along side the tan rocks of the North American Plate. Photograph copyright by David Lynch.
What an amazing location. I believe that only in California can you see the boundary between two tectonic plates so clearly. And yes, if I went there, I’d have someone take a picture of me standing astride the fault.
Here’s a silly shot from San Andreas.org (it’s not about the people, it’s about the sign):
And here’s a close-up of the fault in the Carrizo Plain (Pano by Dusty Trail):
I stumbled on a blog (Geotripper) with a cool series of photos (through a 12-year period) where the fault crosses a road. Here’s one of the shots:
Click HERE to check it out.
Just for the heck of it, you might want to check out this “Culture of Life News” website, entitled “We Visit Doomed Homes on the San Andreas Fault.” It’s not written by a scientist, but it is certainly interesting. Here’s one of the photos:
Click HERE for the whole piece.
So, it’s time to post some GE Panoramio shots. I’ll start with this shot by Douglas Page of the road just east of my landing. My landing would be just off the photo to the left:
Here’s a shot about a mile northeast of my landing (also by Mr. Page), showing a rainbow over the San Andreas Fault:
It’s time to move a little further northeast, to the Carrizo Plain. Here’s an amazing landscape captured by peace-on-earth.org:
Check out this valley overview by Jeffrey A. Hart:
And this other-worldly shot by NatureNerd:
I’ll close with this, by Bakersfield Cactus:
Worth a trip, eh?
That’ll do it.
© 2015 A Landing A Day