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.

Explore the Pacific Northwest and Northern Rocky Mountains with Geotripper! June 18-July 2, 2026

Grand Tetons National Park, Wyoming

Be forewarned. This post is a TRAP! It is designed to draw you in, weaken your defenses, and cause you to do something different than everyday life. Warning given...

Have you ever dreamed of hitting the open road and finally seeing those places you've dreamed about, but haven't acted on that dream yet? What if you found out about an excursion that doesn't just tour, but allows you to learn the geology and history of those wild places? A tour on which you can even earn college credit? AND, a tour that is affordable? Maybe this is the one...

Mt. Shasta, a Cascade volcano in northern California

From June 18-July 2, 2026, the geology and anthropology departments of Modesto Junior College will be conducting a field studies course (Geology 192/Anthropology 192) in the Pacific Northwest and Northern Rocky Mountains. It will be a six semester unit course designed for our community college clientele: first year geology/anthropology majors, potential majors, as well as community members (especially teachers) and life-long learners interested in geology, archaeology, and natural history. We will develop the necessary geological/anthropology background prior to and in the early days of the trip, so people of all backgrounds are encouraged to attend. The total cost is $850 which will include all food, camp fees, entrance fees, transportation costs for the trip. The tuition cost for the six units of semester credit will be around $380 (out of state tuition is higher). The only additional costs should be for showers, laundry, books and other souvenirs, and junk food (we provide healthy food for the most part; if you want Twinkies you are on your own!). We will be camping each night, and the school provides the transportation (vans). The excellent meals are planned by our professional volunteer staff, and cooked by the participants under their watchful eyes.

Lava Tube in Lava Beds National Monument

What will you see and experience? On the 18th we'll leave MJC and drive north through the Great Valley of California and arrive at the south end of the Cascades Range. The huge edifice of Mt. Shasta looms over the north state at 14,163 feet, and still is potentially active. It last erupted in 1786. Depending on snow conditions, we'll climb to the 8,000 feet level at the old ski bowl and have a close look at the rock and ash deposits. We'll continue north and end the day at Lava Beds National Monument near the Oregon border. There will be chance to explore some lava tubes while we are there.

The view from Smith Rock State Park in Oregon

We drive through Oregon the next day, with possible stops at Crater Lake National Park and Newberry Crater (depending, once again, on snow conditions). Camp will be at Tumalo State Park. The following day we will explore Smith Rock State Park (above), Mt. Hood, and the Columbia River Gorge (if there is time we will climb Beacon Rock in the gorge). The third camp will be at Seaquest State Park at the foot of Mt. St. Helens in southern Washington.

Mt. St. Helens in Washington. It erupted in 1980 and 2004

The following day will be devoted to the exploration of Mt. St. Helens (weather allowing!). We'll then move on to the Pacific Coast and the temperate rainforests of Olympic National Park. We'll visit some tribal lands near the westernmost point of the lower 48 states and explore Hurricane Ridge at Olympic's north side. 

We'll then descend the eastern flank of the Cascades (including a close look at Mt. Rainier) and drive onto the Columbia River Plateau, a vast basalt plain that covers much of eastern Washington and Oregon. Camp will be at Sportsman's State Park in Yakima.

Dry Falls State Park in Washington. The floodwaters covered this entire landscape to a depth of 300 feet during the Spokane floods.

The next day we will view the evidence for vast floods that swept across the plateau during the Pleistocene ice ages. The discovery of these floods by J Harlan Bretz in the 1920s and the long road to acceptance of the hypothesis by the geological community is one of the great stories in the history of geology as a science. We'll have a look at the Channeled Scablands, Soap Lake, and Dry Falls as we travel east through Washington. We'll spend the night at Riverside State Park in Spokane, Washington.

We'll head through the copper mining districts of Idaho and into Montana where we'll see more evidence of the ice age floods. We'll drive east to Lewis and Clark Caverns and stay near Bozeman, Montana. We'll check out the Museum of the Rockies and move on to explore Yellowstone, America's oldest national park. We'll spend two days exploring this incredible park.

Yellowstone Falls in the Grand Canyon of the Yellowstone River

There is the Grand Canyon of Yellowstone, and a menagerie of incredible animals, including elk, bison, moose, bighorn sheep, and if we get really lucky, wolves.

Wolf near Norris Geyser Basin, Yellowstone National Park

Then there are geothermal features for which Yellowstone is so famous. Grand Prismatic Spring, for instance, and 70% of the world's geysers (there's lots more besides just Old Faithful!).

Grand Prismatic Spring, Yellowstone National Park

We'll then head south and spend two days at Grand Tetons National Park with time for some spectacular hikes. Then we start the road home with a drive through northern Nevada.

Big Geyser (not Old Faithful!) in Lower Basin, Yellowstone National Park

It's hard to describe the wonders that exist across the Pacific Northwest and Northern Rocky Mountains without getting an overwhelming urge to get up and leave right away. If you are in the Modesto region, we are having our first information meeting on Monday, March 23 in the Science Community Center on the west campus of the Modesto Junior College at 7 PM in SCC 325 (attendance is not mandatory to go on the trip). We hope you will join us!

I Got Up at 3am So You Wouldn't Have To: The Last Lunar Eclipse Before 2029

I didn't really feel like it, but lunar eclipses are dramatic, and this was the last one to take place until 2029, so I got up a few times between 2am and 4am to snap a few shots of the event

Lunar eclipses happen when the Earth moves in-between the Sun and the Moon, and casts a shadow across the face of the Moon. The shadow is spherical, by the way, so flat-earthers can re-examine their belief system.

The darkened portion of the lunar disk is much darker than the lit portion, and was hard to focus on with my limited photographic equipment.

The red color is due to the red edge of the visible light spectrum being bent through the Earth's atmosphere. It could be kind of cool to see a lunar eclipse from the Moon itself. I assume the Earth would have a red ring around it.

I would have stayed up longer, but my camera (based on previous experience) probably wouldn't focus right, and I had to work today.

One cool aspect of lunar eclipses is that many more stars appear during totality. My phone couldn't focus so much on the Moon, but did show how many stars were visible near the Moon that wouldn't otherwise be visible.

 

Revisiting the Wrightwood Mudflows of Ages Past: That Slope Won't Be a Problem Will It?

Like many others, I've been astonished by the storms of the last few days and the effects across all of California and the Pacific Northwest. It's not quite over, and if you are in one of the danger zones, listen to the emergency workers. They know what they are doing. 

I've been especially attentive to the stories coming out of Wrightwood in Southern California. It's been a well-known trouble spot for many years. Back in 2013, I paid a visit and had a look at the geological conditions that have plagued the area. What follows was posted in March of 2013.

You learn something new everyday. At least I hope you do. I learned something astounding revealed by satellite imagery of the Mojave Desert.

We were headed home a week or two ago, and were taking a "short cut" along the San Andreas fault in Lone Pine Canyon and through the town of Wrightwood. That's right, "through" the town. The village is built on top of the San Andreas! But that's not what I learned. I've known of the close proximity of the fault and the town for years.

It had something to do with the town's other famous natural hazard: the Wrightwood mudflow. There is a slope south of the town heading at an elevation of more than 8,000 feet composed of deeply weathered and crushed Pelona Schist. As can be seen in the picture below, the slope is so steep that trees and shrubs can't gain a roothold, and failures are constant, especially during the spring snowmelt and during heavy rainstorms.
The Pelona schist formed in the accretionary wedge of the subduction zone that lay off the California coast during the Mesozoic Era, and as such may be similar to the Franciscan Complex farther to the north. It is an attractive muscovite mica quartz albite schist in hand samples, but it doesn't do well on steep slopes.

We passed several channels that were clearly designed to send the flows through town without causing further damage.

In May of 1941, just over a million cubic yards of mud and boulders flowed down Heath Canyon and into the town of Wrightwood, damaging and burying a number of structures. No deaths or injuries were reported. The immediate cause was the rapid melting and runoff of the heavy snowpack during a period of unseasonably warm temperatures. Surges of mud continued for a week. Other damaging mudflows occurred in 1969 and 2004.

This basic information was something I was made aware of during my first geology class at Chaffey College many years ago. One thing I didn't know is that the mud passed beyond Wrightwood and continued for 15 miles into the adjacent Mojave Desert. The flow traveled a vertical mile, from 8,000 feet to 3,000 feet.

Source: http://www.wrightwoodcalif.com/mudflows/53SharpRptMud.pdf

The other thing I didn't know is that Wrightwood mudflow has been active for at least five centuries, and that the results of the slide are clearly visible from space! Check out the Google earth image below and note the dark gray alluvial fan just right of center. The gray colored fan is composed of the Pelona schist, which is much darker than the sediments in adjacent fans which contain more granitic rock.

Source: http://epod.usra.edu/blog/2009/06/heath-canyon-landslide.html

The town of Wrightwood is easy to visit. It is just off of Highway 138 west of Cajon Pass on the Angeles Crest Highway. As noted previously, the town sits on the San Andreas fault, so the locality is a good spot to visit and reflect on the many hazards that must be dealt with when one decides to take up residence in the state. For more information on the mudflow, check out this state report: http://www.wrightwoodcalif.com/mudflows/79MortonMudRpt.pdf

The Other California is my on again-off again blog series on the geologically interesting places in our fair state that don't show up on the tourist guides.

Why did the Road Cross the San Andreas Fault? 23 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 37 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 37th time, but in some cases it is not a problem. There are geologic changes that happen on a yearly basis, and with twenty-three 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

Last 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.

And 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

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.

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?