Why did the Road Cross the San Andreas Fault? 24 Years of Geologic Change (a new Update)

2002

I've been leading geology field studies trips to lots of places in the American West for 38 years and started to take digital pictures in 2001. I sometimes struggle to find new things to photograph when I visit a place for the 38th time, but in some cases, it is not a problem. There are geologic changes that happen on a yearly basis, and with twenty-four years of photos (minus two due to Covid), the changes become obvious. This is a continuing update from a post in 2013, and I'll probably continue updating for the foreseeable future.

2004

Highway 25 in the California Coast Ranges connects the town of Hollister with the access road to Pinnacles National Park (formerly Pinnacles National Monument). Along the way the highway crosses the San Andreas fault in a section where the fault creeps an inch or so each year (36°35'54.27"N, 121°11'40.19"W). Most years we've stopped to have a look at the effect the movement has on the pavement. In 2002 and 2004, the damage was obvious.

2008

By 2008 someone had patched the road, and no fault motion was evident.

2009

Little damage was evident in 2009 either. But by 2010 cracks had begun to appear as the fault stressed the pavement.

2010

The fact that the fault creeps in this region is a good thing. It means that stress is not building along the fault surface but instead is being released gradually. The sections of the fault to the north and south of the creeping section are locked by friction and are building up the ominous stress that will eventually produce quakes with magnitudes in the range of 7.5 to 8.0. The quakes are coming and we need to be as prepared as possible.

2012

By 2012, the road had been completely repaved, and  yet the shearing was already evident.

2013

It became even more pronounced by 2013 and in 2014. Just by chance, the person working as a scale was the same individual as in 2004.

2014

In 2015 the fractures were moderately larger. They'll need to start thinking of road repairs before long.

2015

In 2016 Laura once again provided scale, as she did in 2014 and 2004.

2016

Here in 2017, long-time trip volunteer Mary provides scale. The cracks in the road are just a bit larger, but they didn't look appreciably different than the previous year except for a twist (pun intended).

2017

On Dec. 2, 2018, the break to my eye seems more continuous. It's now been six years since the road was completely repaved.

2018

That year the paint was deformed (twisted) but not split (below).

2017

The offset paint strip reminds me of illustrations of elastic rebound theory, the idea that stress builds up on a fault line over time. In that model, the land on either side of the fault is distorted over time until the frictional resistance is overcome and the rock snaps back to its original shape. That won't be happening with the paint. Last year in 2017 I said "if they don't repair the road (as they often do; see above), it will probably show a clear break by next year." Here's what transpired:

First, a close-up on 2017's center stripe...

2017

And here's how it looked on Sunday, Dec. 2, 2018:

2018

As predicted, the break in the paint is complete...

In 2019 (those last few halcyon days before Covid) long-time volunteer Paul provided scale (he has been assisting MJC with field trips for 25 years!). The crack continues to grow, and I wouldn't have been surprised if it was patched by next year.

 The paint on the center strip is split even more.

November 2019

And then Covid happened and for a few years we were not able to conduct our field studies classes. In 2022 we made a return visit with our students and here is the then-current condition of the highway. It didn't appear that any repairs have been conducted yet. Our host is once again Laura, who was with us back in 2004 and subsequent years!

November 2022

Fault creep is not a constant. I didn't see a whole lot of change over the last three years, although I didn't get as many close-up shots. Here's a closer look with Paul, our other long-time volunteer. What do you see that is different?

November 2022

In 2023 the road continued to become more deformed, and the passing traffic produced an audible thump as it passed over the fault. Our host since 2004, Laura, was not able to join us, so her husband Ryan stood in her place.

Oct. 28, 2023

And then it was 2024, October 12 to be specific. Once again our guide is Laura, who has assisted on these trips since at least 2004. The crack continues with minor changes, and it may be overdue for another repaving job.

October 12, 2024

They may not have repaved the highway, but they did in fact repaint the center line, which obscures about two inches of right lateral offset.

That brings us to 2025 (October 11). Our long-time volunteers weren't on the trip this year, so River and Makayla jumped in to provide scale. 

Oct. 11, 2025

Oct. 22, 2025

The road hasn't been repaved since 2012, and the crack is continuing to slip and fracture. The pavement at the road median has fragmented, and completely repainted which hides the offset a bit.

Oct. 10, 2026

It's now 2026 and the road continues to buckle. Tsing and Jo provide scale this year. I'm mildly surprised that the road maintenance crews haven't fixed this section yet.

These little changes that happen at a rate visible in human lifetimes add up to huge changes when multiplied by thousands or millions of years. The nearby eroded volcano of Pinnacles National Park has been displaced 195 miles (315 kilometers) in the last 20 million years or so by movement along the San Andreas.

How will it look next year?

Geotripper Rates Hollywood Movie Geologists (AND, see "Tremors" at the State Theatre on May 20!)

One of my earliest blog posts (in 2008) was a list of my favorite depictions of geologists in movies. I've revisited it once or twice. It came to mind as we prepare to offer a showing of "Tremors" as a geology field studies fundraiser at the State Theatre in Modesto on May 20th at 7 pm. If you would like to attend or donate to our field studies fund, please check out the first comment!

What are the best depictions of geologists in movies? I have the definitive list below! I listed my number one choice, but the others are in random order.

As will be seen from my list, my taste in movies runs towards action-adventure as opposed to the "sophisticated" cinema ("There will be Blood" with Daniel Day-Lewis would otherwise take the top spot). But frankly, no movie with a geologist can exist without action and adventure...

Despite having grown up in southern California, and having lived through the 1971 Sylmar quake, I have never taken a picture of the Hollywood sign, so I offer a photo of a favorite Hollywood set, especially in the old westerns: the cliffs of Red Rock Canyon State Park on Highway 14 in the Mojave Desert. The rocks are Miocene continental floodplain sediments lifted up by fault motions on the Garlock and El Paso fault systems. Dr. Grant should be scaring that little kid with a velociraptor claw any moment now!

My favorite geologists in the movies:

And the winner is: Finn Carter as seismology graduate student Rhonda LeBeck!

1) Tremors (1990): Finn Carter as seismology student Rhonda LeBeck.

Speaking from an entirely gender-biased point of view, Finn wins my vote as the finest portrayal of a geologist in a Hollywood movie. Intelligent and creative, and cute, too. And finding strange underground worm things using a seismometer. The backdrop of the Eastern Sierra Nevada and Alabama Hills was an extra-special plus.

2) San Andreas (2015): Rock (Dwayne Johnson) as a character of some sort, and Paul Giamatti as a paunchy bearded hero geology professor named Hayes. I reviewed the movie in this post from 2015. I was struck that the "hero" of the movie saved around four people, while the "B"-plot geologist saved maybe millions of lives. The movie was also notable for showing a fellow geologist who was Asian (but he died in the movie, of course). 

The real hero of "San Andreas"

3) Volcano (1997): Laurie Latham as Rachel, Anne Heche as Dr. Amy Barnes (honorable mention)

Rachel didn't get much credit for being the first Hollywood geologist to get sucked into a volcano, but she displayed many of the traits of the real geologist: self-effacing, nervous in front of cameras, and yet a good and perceptive researcher. Of course, she wasn't a leading character. The actual 'star' of the film, Anne Heche gets honorable mention for looking at a topographic map on-screen, but then using a basketball to confirm that a street does in fact slope downhill the wrong way.

The smarter of the two geologists in "Volcano" (other than getting sucked into the lava)

4) Dante's Peak (1997): Pierce Brosnan (!) as Dr. Harry Dalton, Charles Hallahan as Paul Dreyfus, Grant Heslov as Greg and others

James Bond as volcanologist?? Well, I dunno...too clean-cut, too shaven, too cultured. Now, the rest of his team, though, they were more like the people I see and work with on a regular basis. Coffee addicts, intense, and lovers of volcanoes. Some of the portrayals of geological processes were done pretty well, except for that really fast-moving Hollywood lava, and driving a truck through said flow without dying from the radiant heat. And that acid lake that killed grandma. And that overly steep giant Hollywood volcano in Idaho (!). I really liked the bridge that got washed out at the end of the movie, though.

Well done, special effects people! Seems like they should have let the van go first, though.

5) King Kong (1976): Rene Auberjonois as Bagley

In his pre-"Deep Space Nine" days, Rene played a geologist who thought that the mysterious uncharted island was hiding a lot of oil. When shown to be wrong, he did what many geologists are known to do...he got drunk.

I think he would have been drunk even if it was oil.

6) Erin Brokovich (2000): Julia Roberts in the title role

The first scene of the movie had Julia Roberts saying "I love geology". I melted on the spot and was hers from that point on. Though she was actually a legal clerk and not a geologist, she was shown researching groundwater chemistry, taking samples of poisoned water, pulling dead rotting animals from wells, and running away from security guards after trespassing on company property. All in a day's work for any field geologist, I should think.

This is why I'm a geologist, not a biologist.

7) Raiders of the Lost Ark (1981): Harrison Ford as Indiana Jones

O.K., so he was really an archaeologist, but he dug in the earth a lot, and the character was said to be based on Roy Chapman Andrews, an adventuring paleontologist who explored the Mongolian deserts in search of ancient life in the 1920's. His expeditions found the now renowned Flaming Cliffs which contained fossils of protoceratops, oviraptor, and that most famous of movie dinosaurs, velociraptor. His party also discovered the nests of some dinosaurs, containing egg clutches in concentric circles, and some very rare Cretaceous mammals. They were chased by bandits and assaulted by horrible dust storms. And what geologist doesn't dream of dramatic adventures in the field? Also, in the third movie there were earthquakes, and the ground opened up and swallowed people!

8) Jurassic Park (1993) and Jurassic Park III (2001): Sam Neill as Dr. Alan Grant.

His character was ok, but I was most impressed by the office trailer for the paleontology dig in Montana; messy, dusty, newspaper clippings on the wall, lunch mixed with research; a true geology office! The third movie in the series mostly had people getting eaten, but as usual, the dinosaurs looked pretty cool.

This looks suspiciously like my own laboratory...

9) The Lost World: Jurassic Park 2 (1997):

Come to think of it, there weren't many paleontologists in this movie, except the guy in cowboy hat with the long beard who looked a lot like Robert Bakker. I think he got eaten by a velociraptor...(Update: I completely forgot that Julianne Moore was most certainly a paleontologist in the movie).

10) The Core (2003):

I don't really remember much about the geologists, but I loved the "element" they used to drill into the mantle and core in only two or three days; it was called "Unobtainium" (which was also in the plot for "Avatar"). And that giant mantle amethyst geode was pretty cool, even if the crystals killed some of the crew members.

11) Bringing Up Baby (1938): Cary Grant as Dr. David Huxley.

Handsome guy, looking for a dinosaur bone with beautiful Katherine Hepburn at her best, a pesky dog and a pair of leopards. What more could you ask?

12) Eight Below (2006): Bruce Greenwood as Dr. David McClaren.

A geologist willing to ride a dogsled for a week, face down avalanches, blizzards, crevasses, frostbite, a broken leg, and a fall into freezing cold water, all so he could find a meteorite in Antarctica. How he knew to look for that particular meteorite on a rocky mountainside as opposed to the surface of a glacier, I don't know. And they left those poor dogs behind....

13) 2012 (2009): Chiwetel Ejiofor as Adrian Helmsley.

2012 was notable for having an African-American as the lead geologist in an otherwise ridiculous movie. He provided the moral center for the hard decisions being made about the future of humanity. I give my students an assignment on finding geologists in movies, and this role comes up more than any other. Woody Harrelson, while not a geologist character, wins honorable mention for best geology-related death in a movie, as he is incinerated by the eruption of the Yellowstone Caldera.

If I'm 95 and sick, I want to go this way too.

While researching for this post, I came across an excellent review of geologists in movies in Earth Magazine which actually analyzes whether geologists were women or minorities, whether they were evil or not, and whether they survived to the end of the movie. I highly recommend it! 

Which movies did I miss? Please contribute to the comments!

George Lucas Had It Wrong. A Day of Intense Pride at Modesto Junior College Yesterday

Going to hyperspace? Not exactly...

George Lucas had it wrong. No, I'm not talking about the prequels to Star Wars! It was something much earlier. People could be forgiven for not knowing this, but Star Wars was not George Lucas's first successful film. He was known for another great movie, American Graffiti, a semi-autobiographical film that recalled his days as a young man in Modesto, California. Yes, Lucas is perhaps our most famous native son. He also attended Modesto Junior College for a time.

So what was it that he got wrong? It was a fairly minor plot point, but in the movie, the two friends Curt and Steve were on the same pathways for their lives. They were planning to leave town to attend a "northeastern" college (let's presume an Ivy League school), but after a series of events over the space of one long night, Steve is convinced to stay in Modesto, attending the "junior" college, while Curt heads off to great success, and was eventually a writer living in Canada. Steve ended up selling insurance in Modesto.

What's wrong with this picture? It was the insinuation that attending a community college was somehow a lesser option for achieving success, that it is in some way a second-rate education. As I sat proudly through our graduation ceremony last night, I would fiercely argue that getting a degree at a community college is a wonderful achievement, and that I would proudly put my students up against any Ivy League student at the two-year mark in their academic career.

It doesn't take long to realize that a lot of (but certainly not all) the students at a Harvard or Yale are children of privilege, people who have never really had to struggle to get ahead in life. They started in private upscale schools, got in on the fast-track to an Ivy League school with the best preparation possible. It's hardly a surprise that they would excel and succeed. They have incredibly high standards for acceptance, and only admit a small percentage of those who apply.

At Modesto Junior College, we have a motto: "We Welcome All; We Serve All". We give anyone the chance to succeed, no matter the circumstances of the lives of our students. And last night 916 students walked the stage, proving they could succeed against all odds.

The students I work with come from many different backgrounds, and most of them are poor and disadvantaged. They come from many cultures. Our elementary and secondary schools are underfunded and sometimes dangerous, and alcoholism and drug use are epidemic in our region. The kids in our schools have the decks stacked against them at every turn. They come to us unprepared and unskilled. We have veterans suffering from PTSD, abused spouses, and laid-off laborers. Many of them are working at two or even three jobs, and are taking care of children. We have huge numbers of people who are the first in their families to ever attend college. We have resources at our school, but sometimes the challenges facing our students are overwhelming. And yet these students persist, and they fight, and they cry, and fail, and then they come back again. And in the end they master the skills required to pass their classes. When you see a group of these students decked out in blue robes, and receiving an AA or AS degree, you are looking at some of the most successful people in the world.

If you are an employer, and you see a community college on the resume of a potential employee, you are looking at a person with persistence, stamina, and an incredible work ethic. They've been through impossible challenges and they've succeeded.

I couldn't be more proud of my students on this great day.

Geotripper and two geology graduates!

One of California's Rarest Ecosystems: The Serpentine Soils of the Red Hills

 The Red Hills are blooming right now, so I am posting an abridged version of my post from May 21, 2021 explaining the geological conditions that formed the unique landscape.

Imagine a world turned upside down and inside out. A place where the underworld realm is exposed to view, where all is out of equilibrium. It sounds like the introduction to a dystopian horror movie, but in this case, it is a description of one of the truly rare and unique ecosystems in California: the serpentine soils. 

The Red Hills Area of Critical Environmental Concern is a rather clumsy name for one of the most unique places in all of California. It comes by the name righteously, as can be seen in the Google Earth image above. The soils have a distinct red-brown color, even though the serpentine-rich rocks they come from are generally green or black in color. And these are truly alien rocks. They are not part of the surface realm; they are the materials of the earth's depths, far below the crust that we live on. The earth's mantle lies at depths of 15 to 40 miles beneath the surface and is composed of iron and magnesium-rich minerals like olivine and pyroxene. These minerals may be stable deep within the earth's interior, but if they are exposed at the earth they are out of chemical equilibrium and subject to rapid reactions with oxygen, water, carbon dioxide, and acids in soils. The iron quite literally rusts during oxidation.

The thing about soils rich in iron and magnesium is that they are poor in macronutrients like potassium and calcite, and include some toxins like selenium or nickel. The vast majority of plants cannot tolerate these chemical conditions. But there are a few.

At the west end of Red Hills the oak woodland gives way to a gray pine-ceanothus scrubland

The change is stark. Driving up Red Hills Road from the west, one passes through typical foothills oak woodlands, with a thick covering of grass. And then just like that the grass disappears along with the oaks. One enters an area dominated by Buckbrush with the occasional Foothills Pine (Gray Pine). In many areas, barely any vegetation covers the rocks at all.

The region was long seen as having no particular value. The ultramafic (mantle-derived rocks) were related to the gold-bearing lodes, but rarely had any valuable ores in and of themselves. Despite the Homestead Act in the late 1800s that sought to give citizens free land in the west, there were no takers in the Red Hills. No useful crops could be grown on the soils, which was a requirement for owning the property. For many decades the Red Hills were used as a de facto garbage dump and shooting range.

By the late 1980s the Bureau of Land Management, the federal agency in charge of the Red Hills area, belatedly recognized the unique nature of the ecosystem here, and declared it an "area of critical environmental concern". Clean-ups were organized, and minimal tourists facilities (trails, parking areas, vault toilets, and a nature trail) were constructed. Today the park (why not just call it a park, after all?) is a local favorite for wildflower enthusiasts, birdwatchers, and hikers, especially in the spring.

So what is the geologic story of this strange and wonderful landscape?

The Mother Lode is famous as the source of the ores during the Gold Rush in 1848-53, and many people know of the association of quartz veins with the gold. What is less known is that the Mother Lode consists mostly of metamorphic rocks like slate, greenstone, and marble, not the granite that is found in the higher parts of the Sierra Nevada. These metamorphic rocks are the twisted and baked remains of sea floor muds and silts, lime from tropical reefs and shelves, and volcanic rock from the oceanic crust. These collections of crustal rocks (called "exotic terranes") were transported across the Pacific Ocean and slammed (in the geologic sense; they moved at maybe 2 inches a year) into the western edge of the North American continent, mostly in the late Paleozoic and Mesozoic eras (the Mesozoic era, from around 251 to 65 million years ago, is best known as the "age of the dinosaurs"). The different terranes are separated from one another by major fault systems.

California Goldfields (Lasthenia californica)

The rocks of the Red Hills were part of the huge fault systems and included slices of the earth's mantle, consisting of the dunite and peridotite mentioned above. The original mantle rocks were mostly metamorphosed into serpentine on their upward journey along the fault systems.

Blue Dicks (Brodiaea) and Poppies

Serpentine (or more properly serpentinite) was declared the California State Rock in the 1960s, in part for its association with asbestos, which is a fibrous crystal form of serpentine. Asbestos was a "wonder mineral" from at least Roman times, as it was fireproof, and could be woven into a fabric. As fire insulation it no doubt saved many lives, but there was a cost. Those who were constantly exposed to asbestos were far more likely to contract a deadly disease called mesothelioma. It is now a cottage industry for people in the business of removing asbestos from older buildings.

There was a political brouhaha in 2010 when some groups tried to change the state rock to something else, but geologists objected on the grounds that it was an appropriate symbol of the state due to the research value of having mantle rocks at the surface, and the value as an ore for other important metals such as chromite (used in armor and stainless steel), and mercury (used original to separate gold from its host ore). The proposed bill was never voted on.

The Red Hills are semiarid with only a few creeks that dry up quickly as the summer progresses. But a few small springs and pools persist through the year and in those pools is an endemic fish, the Red Hills Roach, a distinct subspecies of the California Roach. It is found nowhere else in the world. We saw some of them a few weeks ago during our visit, but the video below is from an earlier, wetter year.

The rest of the photos are some of the flowers we saw this year, some old friends, and one or two new discoveries.

Poppies

Five Spot (Nemophila maculata)

Monkeyflower (Erythranthe sp.)

Bitter root (Lewisia rediviva)

The last flower was one we've not noticed before. It seems to be a Fort Millers Clarkia, but I am open to correction!

Fort Miller Clarkia (?) (Clarkia williamsonii)

There are just a few flowers left in the Red Hills as of last Friday, but to see the spectacular show you'll need to wait until next spring. But...the rocks are always there!

The Red Hills Area of Critical Environmental Concern is in the Sierra Nevada foothills near Chinese Camp off of Highway 120. If you want to learn more, or pay a visit, information about the Red Hills can be found on this BLM website, and the trail and road map can be found here.