Looking back at John McPhee’s Assembling California: A Journey through Geology and Time

Sierra Nevada Mountains and Hot Creek Geological Site (Erik Olsen)

California’s diverse landscapes, rich history, and abundant natural phenomena have inspired many scientific-themed popular books, ranging from John Steinbeck’s “The Log from the Sea of Cortez,” with its focus on marine biology, to Mary Austin’s “The Land of Little Rain,” a lyrical examination of California’s desert environment, not to mention the late Marc Reisner’s Cadillac Desert, an epic history of California’s contentious relationship with water. (I’ve read it twice.)

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But when it comes to exploring the state’s geology – its mountains, coastlines, and, most notably, its fault lines – few books can match the prowess and eloquence of John McPhee’s “Assembling California“. Part of his Pulitzer-winning series, “Annals of the Former World,” the book offers a comprehensive and accessible tour through the geological history of California, crafting a fascinating narrative that is as engaging as it is informative.

John McPhee is an acclaimed American writer and pioneer of creative nonfiction, renowned for his deeply researched and beautifully crafted works that often explore topics related to nature, science, and geography. A long-time staff writer for The New Yorker and the author of over 30 books, McPhee is celebrated for his ability to turn seemingly ordinary subjects—such as geology, oranges, or transportation—into compelling narratives. His distinctive style blends meticulous research with accessible, often poetic prose that has been widely immitated. I’ve read several of McPhee’s books and while some of the work can be hard going, I’m usually very satisfied once I’m done. Assembling California is, in my opinion, one of his best.

Here’s an excerpt:

An old VW bus is best off climbing the Sierra from the west. Often likened to a raised trapdoor, the Sierra has a long and planar western slope and—near the state line—a plunging escarpment facing east. The shape of the Sierra is also like an airfoil, or a woodshed, with its long sloping back and its sheer front. The nineteenth-century geologist Clarence King compared it to “a sea-wave”—a crested ocean roller about to break upon Nevada. The image of the trapdoor best serves the tectonics. Hinged somewhere beneath the Great Valley, and sharply faulted on its eastern face, the range began to rise only a very short geologic time ago—perhaps three million years, or four million years—and it is still rising, still active, continually at play with the Richter scale and occasionally driven by great earthquakes (Owens Valley, 1872). In geologic ages just before the uplift, volcanic andesite flows spread themselves over the terrain like butterscotch syrup over ice cream. Successive andesite flows filled in local landscapes and hardened flat upon them. As the trapdoor rises—as this immense crustal block, the Sierra Nevada, tilts upward—the andesite flows tilt with it, and to see them now in the roadcuts of the interstate is to see the angle of the uplift.
John McPhee in Assembling California

The Sierra Nevada, a massive mountain range stretching like a spine nearly the length of California, provides the central geological narrative in “Assembling California”. Known for its stark beauty and dramatic peaks, the Sierras are also a textbook example of the immense forces that shape our planet. (We’ve written and will continue to write about them.) McPhee masterfully explicates how tectonic activity shaped this terrain over millions of years, giving readers a sense of the awe-inspiring age and dynamism of the Earth.

A brief bit about the man: Born in 1931, McPhee studied at Princeton University and Cambridge, and his writing straddles diverse topics from basketball to nuclear energy. His primary strength lies in his ability to seamlessly interweave complex scientific principles with engrossing human stories (there’s always an interesting character and the heart of his work), making the intricate world of science both comprehensible and enjoyable to the lay reader. His skill and prolificacy have earned him numerous accolades, including the Pulitzer Prize.

Assembling California stands out for its illuminating journey through California’s intricate geological history. Traveling with the late geologist Eldridge Moores of the University of California Davis, McPhee unpacks the layered story of California’s geology from its seismic activity to its unique rock formations. There is an excellent excerpt in a 1992 issue of the New Yorker.

Moores was a renowned geologist known for his significant contributions to understanding the geological history and structure of the Earth, particularly in relation to plate tectonics. Born in 1938 in Phoenix, Arizona, he spent the bulk of his career as a professor of geology at Davis, where his research significantly advanced the theory of plate tectonics. He was particularly interested in the geology of his adopted home state, California. Moores also held the position of President of the Geological Society of America in 1996. Apart from his boundless energy, Moores’ real gift was his vision: his ability to “see” geologic history in a pile of rocks. His passionate teaching style and profound knowledge made him a beloved figure in the field of geology. Moores died in a tragic accident in 2018 while on a field trip in Greece, leaving a significant void in the geology world.

Moores explains to McPhee how the Sierra Nevada range didn’t just emerge from the Earth’s crust, as geologists long thought. Instead, the building blocks bubbled up from faraway rifts in the ocean floor called “spreading centers,” then transported thousands of miles on moving plates and piled up onto the North American continent.

Sierra Nevada Mountains and Owens River (Erik Olsen)

The movement of the Earth’s crust along fault lines, as in the well-known San Andreas Fault, is a central theme of the book. By explaining the shifting of tectonic plates, McPhee brings to life the reality of living in California: a landscape that is constantly, if imperceptibly, in motion. His descriptions of earthquakes, both historic and potential future ones, vividly underscore the seismic hazards associated with residing in the state. McPhee’s ability to humanize these impersonal geologic processes is a testament to his storytelling prowess. You will learn a lot about what happens to the California beneath your feet.

However, “Assembling California” is not just a tale of geological forces. McPhee also weaves in fascinating narratives about gold prospectors and vineyard owners, infusing the state’s human history into its ancient geological story. You really can’t tell the story of modern California without delving into the resource-driven economic narratives that are a fundamental part of the state’s history. We try to do a lot of that in this magazine.

For those who want to go beyond McPhee, another fine author is Simon Winchester, whose “Crack at the End of the World” picks up where McPhee left off, both in terms of theme and approach. Winchester, a British author and journalist known for his popular science writing, explores the devastating 1906 San Francisco earthquake. Like McPhee, Winchester expertly merges detailed geological explanations with human stories, providing a compelling account of one of the most significant natural disasters in American history. This is also a very fine book.

The legacy of “Assembling California” lies not just in its rich storytelling but also in the path it blazed for a new kind of popular science writing – one that’s engaging, comprehensive, and profoundly human. By understanding our planet’s past and the forces that shape it, we are better prepared to navigate its future. As readers, we owe a debt of gratitude to writers like McPhee and Winchester who, through their craft, help us appreciate the intricate dance between the Earth’s geological processes and human civilization.

Since McPhee wrote “Assembling California,” technology has made leaps and bounds in the field of geology. Advancements in technology like LIDAR (Light Detection and Ranging), which uses lasers to measure distances and can create high-resolution maps of the Earth’s surface, and improvements in seismograph technology and satellite imaging, have allowed scientists to study geological phenomena in greater detail and with better accuracy.

Geology, like all scientific disciplines, evolves over time as new techniques and technologies become available. This progress often refines our understanding of geological phenomena and can lead to new theories and models. We’re still learning a lot about how our state literally came together, with new research being done all the time that sheds light on our mountains, coasts and valleys.

More recent studies of the San Andreas Fault, for instance, have allowed us to better understand the fault’s behavior, including how frequently significant earthquakes occur and what triggers them. For example a 2022 study from Lamont-Doherty Earth Observatory suggests that the San Andreas Fault moves slowly in a process called “creep,” which was previously thought to release tectonic stress and reduce earthquake risk. However, this new research suggests that this creeping segment might instead be accumulating stress, potentially leading to larger and more destructive earthquakes than previously anticipated.

Not exactly good news, but it’s always better to know what’s happening and to have science that backs it up, and McvPhee was a master at helping us understand he way the world works.

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California’s Monterey Formation: Unraveling the Secrets of a Fossil-Rich, Oil-Bearing Geological Wonder

Monterey Formation rocks near Newport Beach (Erik Olsen)

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California’s Monterey Formation is one of the most fascinating geological formations in the United States. Stretching along the California coast from San Francisco to Los Angeles, this formation is notable for its incredible diversity of siliceous rocks—rocks rich in silica, such as shale, chert, diatomite, and porcelanite. While these rocks are interesting to geologists, the Monterey Formation is also significant for its potential to explain the origins of petroleum deposits that have fueled California’s economy for over a century. NASA’s Jet Propulsion Laboratory once called it “California’s primary petroleum source rock.”

Fracture network of joints and cross-joints exposed on bedding surface of siliceous shale. Note linked, larger-aperture fracture in center with oxidation rim. Montaña de Oro State Park. (NASA JPL)

At the heart of the Monterey Formation’s geology is the unique composition of many different types of rock that come together in such a way that they create an ideal environment for trapping oil. The intricate layering of organic-rich shales, siliceous rocks, carbonates, and diatomites forms a complex network of porous and permeable spaces, allowing oil to migrate into these reservoirs. Over time, these rocks act like natural sponges, effectively capturing and holding large quantities of oil within their formations, making the Monterey Formation one of California’s most significant petroleum sources. It is estimated that over 38 billion barrels of oil have been produced to date from fields whose source rock is the Monterey.

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Diatomite, a light, porous rock formed from the fossilized remains of diatoms, is a dominant feature. Diatoms, microscopic algae with silica-based cell walls, thrived in nutrient-rich waters, leading to the thick layers of sediments that later became diatomite. Chert, another key rock type in the formation, is formed from the recrystallization of biogenic silica, adding to the complexity of the geological record. Interspersed with these are organic-rich shales, which contain substantial amounts of organic material called kerogen. Over millions of years, kerogen undergoes a biological transformation becoming the oil and gas that now serve as the backbone of California’s petroleum industry (see our story on the history of the Long Beach oil industry).

The Monterey Formation displays a fascinating and unusual mixture of geological deposits, from deep ocean basins to shallow continental shelves. During the Miocene, upwelling currents along the California coast brought nutrient-rich waters to the surface, fostering high biological productivity and depositing vast amounts of biogenic silica, a form of silicon dioxide (SiO₂) that is produced by living organisms. Periods of fluctuating sea levels, driven by climate changes and tectonic shifts, further shaped the environment. During low sea levels, parts of the continental shelf were exposed, allowing for erosion from wind and sun. These would shift to periods of high sea levels, which allowed for denser, deep-water sedimentation. In some layers, the presence of evaporites—minerals that form from the evaporation of water—suggests extensive episodes of arid conditions, similar to what we are experiencing now with California’s recurring periods of drought.

Offshore oil platforms along California’s coast drill into the Monterey Formation, either tapping directly into its fractured shale or extracting oil that has migrated into more porous sandstone reservoirs. (Photo: Erik Olsen)

Much of the pioneering research on the geology, formation, and unique composition of the Monterey Formation was conducted by the late Robert Garrison, a distinguished professor of oceanography at the University of California, Santa Cruz. Garrison was considered the foremost expert on the Monterey Foundation, and his work was instrumental in revealing how the Monterey Formation’s diatomaceous and phosphatic deposits were shaped by a combination of oceanographic upwelling, climatic shifts, and tectonic activity during the Miocene epoch.

Petroleum geologists find the Monterey Formation especially intriguing because it serves as both a source and a reservoir for oil and gas, allowing them to better understand the processes of oil and gas generation, migration, and accumulation, as well as to develop more efficient extraction methods to maximize its economic potential. They are also quite beautiful. Walk along the beach near Crystal Cove in Orange County, for example, and examples of Monterey Formation rocks abound.

Monterey Formation rocks near Little Corona in Newport Beach (Erik Olsen)

Oil is formed from the remains of ancient marine organisms, such as plankton and algae, that were buried under layers of sediment and subjected to heat and pressure over millions of years, transforming them into hydrocarbons. Some of these hydrocarbons migrated into more permeable rocks, creating substantial oil fields that have been exploited for decades in Southern California. Certain layers of the Monterey Formation, particularly the fractured chert and dolomitic sections, also serve as excellent reservoirs due to their porosity and permeability, allowing them to store oil and gas for long periods of time.

Beyond its geological and economic importance, the Monterey Formation is a treasure trove for paleontologists. Its layers preserve a variety of marine fossils, including diatoms, radiolarians, foraminifera, and coccolithophores. These microfossils offer a detailed look at past ocean conditions, helping scientists reconstruct the climatic and oceanographic history of the Miocene epoch. Additionally, the formation contains fossils of larger marine vertebrates, such as whales, seals, and fish, providing further insight into the ecosystems of ancient oceans.

Microscope image of microfossils and organic matter in Monterey rocks. (Cal State Long Beach)

However, the Monterey Formation is not just a source of knowledge and resources; it also presents challenges, particularly in terms of potential environmental harm and geohazards like landslides. The soft, diatomaceous earth layers within the formation are prone to landslides, especially when water-saturated or fractured by tectonic action. This makes some coastal areas of California, where the Monterey Formation is exposed, particularly vulnerable to slope instability, posing risks for construction and development. Many recent news stories have documented the increasing rate at which the California coast is tumbling into the sea. An excellent recent book on the subject is Rosanna Xia’s California Against the Sea: Visions for Our Vanishing Coastline.

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California’s geology is a remarkable mosaic that tells a story of immense geological diversity and dynamic processes. Among its many treasures, the Monterey Formation stands out as a geological marvel—its intricate layers, rich fossil beds, and significant economic potential continue to captivate scientists and researchers from around the world. This unique formation is more than just rock; it is a time capsule that preserves millions of years of Earth’s history, from ancient marine ecosystems to dramatic shifts in climate and tectonic activity. As geologists, paleontologists, and environmental scientists delve deeper into its mysteries, the Monterey Formation reveals invaluable clues about the past while shaping our understanding of California’s ever-evolving landscape. It serves as a profound reminder of the powerful forces that have sculpted one of the most geologically varied regions on the planet and continues to inspire exploration and discovery in the fields of Earth science.

Why Parkfield, California is the Nation’s Earthquake Capital

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When Big Joe Turner sang “Shake, Rattle and Roll,” he probably wasn’t thinking about a dusty little town in Central California, but in Parkfield, it’s practically the town motto.

Parkfield, California, is a quiet, dusty farming town tucked into the rolling hills of the Cholame Valley, just off Highway 46 (worth the drive if you ever have the chance). A few miles down the road lies an historic intersection, the place where James Dean was killed in a near head on collision crash in his Porsche 550 Spyder on September 30, 1955. The collision ended a blazing young career just as it was taking off and cemented Dean’s image as a tragic icon of American cinema. While tourists still visit the nearby memorial, Parkfield itself is better known to scientists than to star-watchers.

Parkfield is an unremarkable town, with one exception: it lies directly atop the San Andreas Fault and is known as the Earthquake Capital of the World. This is not because there are so many earthquakes there, although there are, but because it has one of the highest densities of seismic technology anywhere. In addition to the larger magnitude 6.0 earthquakes that tend to strike about every 22 years, Parkfield also experiences a steady rhythm of smaller quakes. These minor tremors, often below magnitude 1.0, happen with such regularity, that scientists have compared them to “seismic pulsars” for their consistent, almost clock-like behavior. (And for what it’s worth, Petrolia, California actually has the most earthquakes).

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The San Andreas Fault is one of the best known, and most active faults in the world. In the Parkfield area, the San Andreas Fault is constantly shifting—millimeter by millimeter, day by day. This continuous movement is unique to the region, as the fault remains relatively locked in both the northern section around San Francisco and the southern section near Palmdale. While the fault in these other areas stays immobile, the central part near Parkfield steadily creeps, creating a contrast that puts pressure on the locked sections to the north and south.

Parkfield’s main strip, stretching just a quarter mile, hosts a small collection of buildings, including a one-room elementary school, the USGS-Berkeley earthquake monitoring site, a Cal Fire station, and the Parkfield Cafe and Lodge. Outside the cafe, a row of mismatched mailboxes serves the dozen or so homes scattered along a few dirt roads branching off the main street. Parkfield might be a small, obscure town to most Californians, but to geologists fascinated by the workings of the Earth, it’s the epicenter of seismic research.

Every hillside and valley, grassy nook and riverbed is home to some kind of instrument that measures earthquakes. Over the years, these instruments have become more sophisticated and expensive, making it necessary in many cases to fence them off with the threat of arrest. These instruments monitor, hour by hour, or better, millisecond by millisecond, the stirrings of the earth. To geologists, it is ground zero for seismic measurement.

The town is proud of its reputation. A water tower boasts the tourism slogan: BE HERE WHEN IT HAPPENS (see photo). There is also an iron bridge in the town that has the distinction of standing astride the San Andreas Fault. One one side of the creek that runs beneath the bridge is the North American tectonic plate. On the other is the Pacific tectonic plate. Those two plates are moving south and north respectively at a rate of about 2 inches a year. As we all know, that movement creates immense pressure as the two plates seem otherwise locked in place. That pressure will have to be released at some point. It always has. When that happens, we can expect a potentially devastating earthquake that will rock the state from top to bottom.

The writer Simon Winchester calls the fault an “ever-evolving giant that slumbers lightly under the earth’s surface and stirs, dangerously and often, according to its own whims and its own rules.”

Since 1985, a focused earthquake prediction experiment has been in progress in Parkfield. Known as “The Parkfield Experiment“, the project’s stated purpose is to “better understand the physics of earthquakes — what actually happens on the fault and in the surrounding region before, during and after an earthquake.”

Since the mid-1980s, scientists have deployed an array of advanced monitoring devices, including seismometers, strainmeters, creepmeters, and GPS sensors, to capture detailed data on ground movement and strain accumulation. These instruments are designed to measure subtle changes in the Earth’s crust, helping researchers predict seismic events and understand the processes leading up to an earthquake. By continuously collecting data, the experiment has provided valuable insights into the mechanics of fault movement and the potential for earthquake prediction.

An art installation, known as the Parkfield Interventional EQ Fieldwork (PIEQF), used earthquake waves recorded by the USGS seismic network in California to trigger a hydraulic shake table which was installed in an excavated trench. (USGS)

Experts also once bored a 10,000-foot-deep hole into the ground in Parkfield, into which they placed a large array of sensors to measure the earth’s movements. The goal of the $300 million project, called the San Andreas Fault Observatory at Depth, or SAFOD, was to allow scientists to study how faults work and how earthquakes happen. The drilling stopped in 2007, but Parkfield remains a hot spot for geologic research.

Additionally, the Berkeley Seismological Laboratory operates the High-Resolution Seismic Network (HRSN) in the Parkfield area. This network comprises geophone arrays aimed at monitoring microseismicity along the San Andreas Fault, providing valuable data on the fault’s behavior.

Parkfield remains critical to better understanding seismic dangers in California. The fault zone is poorly understood at depth and so far, the predictability of earthquakes in the near term is pretty limited. But devices like these could help improve prediction, especially if there is a large quake. But that’s the rub, really. We need to experience a large earthquake to get the best data to know how to predict later ones. So it is in California.

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The Pacific Coast Highway (PCH): Icon of American Scenic Roadways

Pacific Coast Highway near Big Sur (Erik Olsen)

The Pacific Coast Highway (PCH), also known as California State Route 1, is one of the most iconic roads in the United States, renowned for its breathtaking views of the Pacific Ocean and rugged coastline. This scenic highway stretches over 650 miles from Dana Point in Orange County in Southern California to Mendocino County in Northern California, offering travelers unparalleled vistas and a quintessential Californian road trip experience. While some suggest that PCH runs from Mexico to Canada, that is mistaken. U.S. Route 101 continues north from California, running along the coast through Oregon and Washington, up to the Olympic Peninsula. That said, it is still the longest state route in California and the second-longest in the US after Montana Highway 200. The story of its construction is as dramatic and intricate as the landscape it traverses.

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The origins of the Pacific Coast Highway date back to the early 20th century, when the automobile was becoming an essential part of American life. The idea for a coastal highway was initially conceived to connect the state’s isolated coastal communities and improve access to California’s scenic beauty. The concept gained traction in the 1910s and 1920s, and construction began in earnest in the 1930s, to provide jobs during the Great Depression.

Lovely aerial of Pacific Coast Highway in Central California

“It took decades to get the highway built,” Carina Monica Montoya told the Los Angeles Times. Montoya is the author of, “Pacific Coast Highway In Los Angeles County” (The History Press, 2014).

The construction of the PCH was an engineering marvel, given the challenging terrain it had to navigate. The road had to be carved out of steep cliffs, cross numerous rivers, and be supported by bridges spanning deep ravines. One of the most significant and iconic portions of the highway, the Big Sur section, presented formidable challenges. This stretch of the road, which runs between San Simeon and Carmel, required extensive blasting and drilling into the rugged coastal mountains. The effort was spearheaded by the California Division of Highways (now CalTrans), with a workforce comprising both state employees and workers from the Civilian Conservation Corps (CCC), a New Deal program.

Key figures in the design and construction of the PCH included engineers and architects who had to innovate continuously to address the formidable natural obstacles. One notable engineer was John D. Isaacs, a prominent builder who contributed to the design and construction of several key bridges along the PCH, including the famous Bixby Creek Bridge. His innovative approach to bridge engineering helped overcome the difficulties presented by the steep canyons and coastal bluffs.

The Pacific Coast Highway took decades to complete fully, with different sections being opened to the public at various times. The Big Sur segment, for example, was officially completed in 1937 after nearly 18 years of labor. The total cost of constructing the highway is difficult to pinpoint precisely, given its piecemeal development, but it ran into tens of millions of dollars—an immense sum at the time.

The Pacific Coast Highway near Santa Monica, California, circa 1930s.

Several colorful characters also play a role in the highway’s history. The Pacific Coast Highway might not exist today if May Rindge, a resolute landowner, had succeeded in her long battle against the county. Since at least the 1890s, a primitive road, often submerged at high tide, hugged the rocky coast between Santa Monica and Malibu, passing under a natural arch and ending at a locked gate on Rindge’s 17,000-acre ranch.

As the owner of Rancho Topanga Malibu Sequit, Rindge was determined to protect her property. She and her late husband had long fought to keep homesteaders off their land. In 1906, she even forced the Southern Pacific Railroad to divert its Santa Barbara line around Malibu and through the San Fernando Valley.

In 1907, when the county proposed extending the coastal road through Malibu, Rindge posted armed guards at the entrances to her ranch and contested the county’s power of eminent domain in court. A stalemate ensued for years, but the road’s prospects improved in the early 1920s when it was included in the planned Roosevelt Highway. In 1923, the U.S. Supreme Court upheld the county’s right to appropriate the land for the highway, and in 1925, a superior court judge granted the county title to the right-of-way in exchange for $107,289, finally ending the dispute.

The book “The King and Queen of Malibu: The True Story of the Battle for Paradise” by David K. Randall (2016) tells the story of Ringe and a wonderful history of Malibu.

Today, the Pacific Coast Highway is one of the most famous and iconic strips of road in the world. Featured in countless commercials as well as movies and TV shoots, sections of PCH are immediately recognizable. Of course, it helps a lot that the highway in in such close proximity to legions of DPs (Directors of Photography) who live in Los Angeles and work in commercials and film. Shooting on the highway is an easy day trip from LA and Hollywood, although it can be difficult to get permits to film on the highway given it is such a busy working road.

That said, the highway faces significant challenges due to climate change and coastal erosion. Rising sea levels and increased storm activity are accelerating the natural erosion processes along California’s coast. This has led to frequent landslides and road closures, particularly in the Big Sur region. One notable event was the massive landslide in 2017 at Mud Creek, which buried a section of the highway under 40 feet of debris, closing it for over a year and requiring extensive repairs. A timelapse of the landslide produced by the United States Geological Service can be seen here.

The Pacific Coast Highway in Newport Beach (Erik Olsen)

The New Yorker ran a piece on the concerns about the highway’s future viability as a means to travel long distances along the coast.

The Washington Post wrote back in 2021, “the engineering folly of a road built on sheer cliffs has meant that closures are annual events — the “whens,” not “ifs” — for the people and the economy it supports.”

The most recent slide to afflict the region took place in April 2024 following heavy rains, when large chunks of the road broke off, tumbling down a cliff and into the ocean near Rock Creek Bridge. Safety officials closed off about 40 miles of road as crews worked to assess the damage and stabilize the road.

Rosanna Xia, a reporter for the Los Angeles Times, masterfully chronicles the problems facing PCH and the California coast in general due to climate change and erosion in her book California Against the Sea: Visions for Our Vanishing Coastline.

Although the Pacific Coast Highway remains one of the greatest road trip routes of all time, the challenges in maintaining its full length are significant for the state and its residents. Despite its enduring popularity, the highway often operates in sections due to frequent closures and repairs caused by natural disasters like landslides, erosion, and wildfires. These ongoing issues demand substantial resources and effort to keep the entire highway operational, making its full-length service a constant struggle.

Still, it remains a pretty excellent place to take a drive. As the Boss once put it, roll down the window and let the wind blow back your hair.

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Black Gold Beach or How Oil Transformed Long Beach and Built the Southern California Economy

Signal Hill oil development (Photo: The Huntington Library, Art Museum, and Botanical Gardens)

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Southern California is best known for its sun-soaked beaches and Hollywood glamour, but it also has a wilder, largely forgotten past: it was once an oil kingdom. It’s a story even many Californians don’t know, a tale of spectacular gushers, fortunes won and lost, and larger-than-life characters straight out of a movie. Without oil, Los Angeles, and much of Southern California, would be very different places today.

The story of oil in Southern California is inextricably linked to the Long Beach fields, an area that once seemed more like a scene from Texas or There Will Be Blood than the Golden State. The discovery of oil in this region wasn’t just a footnote in economic journals; it was a seismic event that transformed the landscape, both literally and metaphorically. And it provided an industrial center of gravity to a region of the state that was just beginning to emerge as one of the world’s great gateways of commerce.

The early 20th century was the beginning of the era of oil in California. On June 23, 1921 at 9:30 a.m., the Alamitos No. 1 oil well on Signal Hill in Long Beach was drilling 2,765 feet beneath the surface when the drill struck an underground oil deposit. This oil was under high pressure due to natural gas, blowing a gusher of oil over 100 feet high, and heralding the start of the Long Beach oil boom.

This event marked the discovery of one of the most prolific oil fields in the Los Angeles basin. Throughout the 1920s, Signal Hill, along with the nearby Santa Fe Springs field, experienced numerous blowouts, which erupted into dramatic pillars of flame that could be seen for miles. These incidents eventually prompted calls for stricter safety regulations. Consequently, in 1929, the state mandated the use of blow-out prevention equipment on all oil wells drilled in California.

Signal Hill quickly mushroomed into a forest of oil derricks, with fortunes being made overnight. As one of the most productive oil fields in the world, the Long Beach field was at one point yielding a staggering one-third of California’s total oil production. By the mid-1920s, California was producing nearly a quarter of the world’s entire petroleum supply, much of it from the Long Beach area.

Signal Hill, Long Beach oil development. (Public domain)

That so much oil is present beneath the surface of this stretch of Southern California is a gift of geology. Millions of years ago, the area that is now Long Beach was covered by the ocean. This marine environment was ideal for the accumulation of organic material, such as the remains of tiny plants and animals, on the ocean floor.

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Over time, layers of sediment buried this organic matter. The high pressure and temperatures associated with deep burial initiated the transformation of this organic material into hydrocarbons – essentially, the formation of oil. Southern California is, of course, known for its active tectonics, influenced by the Pacific and North American Plate boundary. This tectonic activity has created a complex network of faults and folds in the earth’s crust in the Long Beach area.

The folding of the earth’s layers into anticlines (a type of fold that is convex up and has its oldest beds at its core) and the formation of fault traps (where displaced rocks create a seal that traps oil) are particularly important. These structures create reservoirs where oil can accumulate and be preserved over geological time scales.

As the oil flowed, so did the stories of those who sought their fortune in black gold. Perhaps the most famous of these was Edward L. Doheny, a name synonymous with California oil. Doheny, an ambitious prospector, was one of the first to recognize the potential of the Los Angeles Basin’s oil fields. His success in the oil industry was meteoric, but it was not without controversy, as he was later embroiled in the infamous Teapot Dome scandal.

Portrait of oil magnate Edward L. Doheny (Wikipedia)

The impact of oil production in Southern California extended beyond economics. It reshaped the region’s landscape, both physically and culturally. Towns sprung up around oil fields, and workers flocked to the area, drawn by the promise of jobs and prosperity. Long Beach, once a sleepy coastal town, burgeoned into a bustling city.

During the 1920s, regulations on well spacing were minimal, allowing Signal Hill to market narrow town lots. These lots were swiftly purchased by aspiring oil tycoons who installed wells so close to each other that they almost touched. Despite the dense placement, the wells generally remained profitable, though they rapidly depleted the oil field. The hill earned the nickname “Porcupine Hill” due to its appearance from afar, bristling with numerous wooden oil derricks since the more compact “nodding-donkey” pumpjack had not yet been developed.

The booming oil industry in the region attracted a massive influx of workers and investments. As oil fields expanded, Long Beach rapidly transformed from a seaside resort into an industrial powerhouse. The surge in economic activity and the availability of abundant oil fueled the growth of industries in and around Long Beach, including the burgeoning shipping and maritime sectors.

Container ships outside the Port of Los Angeles during the Covid lockdown in 2020. (Photo: Erik Olsen)

The construction of the Port of Los Angeles, which began in earnest in the early 1900s, was driven by the need to support the growing economic activities in Southern California, including agriculture, manufacturing, and oil. The proximity of Long Beach to the port, only about 20 miles south, meant that it was strategically positioned to benefit from and contribute to the port’s activities. The port served as a critical node for shipping oil, among other goods, which further integrated Long Beach, and Southern California as a whole, into the global trade system.

Signal Hill in Long Beach today. (Erik Olsen)

Moreover, the infrastructure developments necessary to support the oil industry, such as roads, railroads, and later pipelines, also facilitated the growth of the port. These developments enhanced the logistical capabilities of the region, making it more attractive for commercial and industrial activities. The oil boom thus not only transformed Long Beach but also had a cascading effect on the development of the Port of Los Angeles, cementing the region’s role as a vital hub in international trade and commerce.

As big and diverse in industry Los Angeles has become, it mostly started with oil. The fact that Los Angeles is now hardly known for oil, but better known for its massive entertainment and tourism economies is an astonishing transformation.

Of course, the influx of wealth and people also brought challenges, including environmental concerns and the need for regulatory oversight. It is well known that several major oil spills have taken place off the coast, ruining beaches and killing animals by the millions. In 1969, the Santa Barbara oil spill released vast quantities of oil into the ocean, creating an environmental disaster along the California coastline. This catastrophic event galvanized public awareness and activism, leading to the creation of the first Earth Day, as well as significant environmental legislation, including the establishment of the U.S. Environmental Protection Agency.

The oil slick visible around Platform A in the Santa Barbara Channel emanated from fissures in the seabed. (Photo: USGS)

Oil spills continue to take place in Southern California and the existence of 26 rigs off the coast are a reminder of that oil boom era. Those rigs are coming to the end of their productive life, however, and an on-gong controversy is what to do with them. Remove them or leave them — or part of them — as artificial reefs?

Over time, oil production in Southern California has waxed and waned. The easily accessible oil has largely been extracted, and production has declined from its mid-20th-century peak. Yet, the legacy of this era persists. It’s etched into the region’s physical and cultural landscape, from the bobbing oil derricks still dotting Signal Hill to the fortunes and institutions built on oil money.

The story of oil in Southern California, particularly the Long Beach fields, is a saga of geologic luck, ambition, ingenuity, and, at times, dangerous greed. It’s a chapter in the state’s history that’s as rich and complex as the oil that still lies beneath its surface, and yet it remains largely unknown to many people who think of Southern California as a paradise of sand and rolling waves.

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Geologist Thomas Dibblee Jr. and the Theory Behind Pinnacles National Park’s 200-Mile Tectonic Journey

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Pinnacles National Park’s open landscape of dramatic rock formations and craggy spires looks otherworldly, especially in golden hour light. But few people who visit the park, located in Central California, southeast of the San Francisco Bay Area, are aware that the rock formations were once at the center of a fierce debate in the history of California geology.

And at the center of the controversy was a young geologist named Thomas Dibblee Jr.

Pinnacles National Park, formerly Pinnacles National Monument, tells the story of ancient volcanic activity and the relentless geologic forces of the San Andreas Fault. This fault, a major boundary between the Pacific and North American tectonic plates, is the platform for the dramatic northward journey of the park’s volcanic remnants. Dibblee’s research illuminated how, over millions of years, the landscapes we see today were sculpted by the movements of these tectonic plates and how the shape of California as a state has changed dramatically as a result.

The crux of Dibblee’s discovery lies in the relationship between Pinnacles National Park and a volcanic source located near present-day Neenach, close to Palmdale in Southern California. The geological narrative that Dibblee pieced together revealed that the rock formations at Pinnacles originated from volcanic eruptions that occurred approximately 23 million years ago, near what is now Neenach. Over millions of years, the relentless movement along the San Andreas Fault has transported these formations over 195 miles (314 kilometers) to their current location. At the time, very few people, geologists included, believed that was possible.

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Dibblee had to be wrong. But it turned out, he was not, and his measurements and discovery launched a passionate debate about the speed of geologic forces.

Dibblee’s findings not only shed light on the significant distances that landscapes can travel over geological timeframes but also provided a tangible connection between the theory of plate tectonics and observable geological features. The juxtaposition of Pinnacles National Park and the Neenach volcanic formation serves as a clear indicator of the San Andreas Fault’s role in shaping California’s geological, indeed it’s physical, identity.

A key aspect of Dibblee’s methodology was his keen observational skills, which enabled him to recognize that the rocks at Pinnacles National Park were strikingly similar in composition and age to those near Neenach, even though these areas are separated by about 195 miles (314 kilometers) today. He noted the volcanic origins of these formations and, through detailed mapping, was able to correlate specific rock types and strata between these distant locations.

Another crucial element in Dibblee’s discovery was his understanding of the San Andreas Fault as a major geological feature capable of significant lateral movement (remember the San Andreas is a slip or sliding fault). By correlating the age and type of rocks across this fault line, Dibblee inferred that the only plausible explanation for the similarity between the rocks at Pinnacles and those near Neenach was that they had once been part of the same volcanic field, which had been split and displaced over millions of years due to the movement of the San Andreas Fault.

Rock formations at Pinnacles National Park (Brocken Inaglory)

Dibblee’s work also benefited from the broader scientific context of his time, particularly the emerging theory of plate tectonics in the mid-20th century. This theoretical framework provided a mechanism for understanding how large-scale movements of the Earth’s crust could result in the displacement of geological formations over vast distances. Dibblee’s findings at Pinnacles and Neenach became a compelling piece of evidence supporting the theory of plate tectonics, showcasing the San Andreas Fault’s role in shaping California’s landscape.

But Dibblee’s ideas were controversial at the time. Many in the scientific community were hesitant to embrace a theory that suggested such dramatic movement across the Earth’s crust, partly because it challenged existing paradigms and partly due to the limitations of the geological evidence available at the time. The prevailing theories favored more static models of the earth’s crust, with changes occurring slowly over immense periods. Dibblee’s insights into tectonic movements and the geological history of regions like the Pinnacles National Park were ahead of their time and laid the groundwork for the acceptance of plate tectonics.

This Pinnacles revelation was groundbreaking, emphasizing the dynamic and ever-changing nature of the Earth’s surface. Dibblee’s ability to piece together these monumental shifts in the Earth’s crust from his detailed maps and observations has left a lasting impact on our understanding of geological processes. His work at Pinnacles and the recognition of its journey alongside the San Andreas Fault underscores the importance of detailed geological mapping in unraveling the Earth’s complex history.

San Andreas Fault looking northwest onto the Carrizo Plain (John Wiley)

Born in 1911 in Santa Barbara, California, Dibblee’s life and work were deeply intertwined with the rugged terrains and picturesque landscapes of the Golden State, Dibblee’s journey into geology began at a young age, fostered by his natural curiosity and the geological richness of his native state.

After earning his degree from Stanford in 1936, Dibblee embarked on his professional journey with Union Oil, later moving to Richfield. It was during this period that his extensive field mapping efforts culminated in the discovery of the Russell Ranch oil field near New Cuyama. By 1952, Dibblee had meticulously mapped every sedimentary basin in California with potential for oil, cementing his legendary status as a petroleum geologist. His reputation for traversing the state’s backcountry on foot for extended weeks became a defining aspect of his character and contributed to his storied career in geology.

Dibblee moved on to a career at the United States Geological Survey (USGS) that would span over six decades, much of it spent with the agency and then later through independent projects. His work ethic and passion for fieldwork were unparalleled; Dibblee was known for his meticulous and comprehensive approach, often spending long days in the field, mapping out California’s complex strata with precision and care.

Over his career, Dibblee mapped over 240,000 square kilometers of California’s terrain, an achievement that provided an invaluable resource for understanding the state’s geological history and structure. He mapped large swaths of the Mojave Desert, the Coast Range and the Los Padres National Forest, earning a presidential volunteer action award in 1983 from President Reagan.

His maps are celebrated for their accuracy and detail, serving as critical tools for academic research, oil exploration, environmental planning, and education. The Dibblee Geological Foundation, established to honor his work, continues to publish these maps, ensuring that his legacy lives on.

Dibblee’s insights into the geology of California were pivotal in several areas, including the understanding of the San Andreas Fault, a major fault line that has been the focus of extensive seismic research due to its potential for large earthquakes. Dibblee’s mapping efforts helped to clarify the fault’s characteristics and behavior, contributing to our understanding of earthquake risks in California and aiding in the development of safer building practices and disaster preparedness strategies.

Furthermore, Dibblee’s work shed light on the process of plate tectonics and the geological history of the western United States. His observations and mapping of sedimentary formations and fault systems in California provided empirical evidence that supported the theory of plate tectonics, a cornerstone of modern geology that explains the movement of the Earth’s lithospheric plates and the formation of various geological features.

Thomas Dibblee Jr.’s contributions to the field of geology are not just confined to his maps and scientific discoveries. He was also a mentor and inspiration to many aspiring geologists, sharing his knowledge and passion for the Earth’s history through lectures, field trips, and personal guidance. His dedication to his work and his ability to convey complex geological concepts in an accessible manner made him a respected figure among his peers and students alike. Through his dedication and pioneering work, Dibblee has left an indelible mark on the field of geology, making him a true giant in the scientific exploration of California as well as our planet.

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Roadcut Revelations: Unearthing California’s Deep History Along the Highway

Roadcut in Southern California on Angeles Crest Highway (Photo: Erik Olsen)

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“Man is a geologic agent,” the late California geologist Eldridge Moores.

Roadcuts in California, those slices through hills and mountainsides made during the construction of roads, are like open books to geologists. They reveal the intricate and often dramatic geological history of the state. When you drive along the highways of California, you’re likely to pass by these exposed cliffs of rock. To the everyday traveler, they might just be a part of the landscape, but to geologists, they are invaluable windows into the Earth’s past.

““Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave,” wrote the great geology (and many other topics) writer John McPhee in his excellent book Annals of the Former World. “To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrane.”

Glacier carved domes tell the story of thousands of years of glaciation in California. (Photo: Erik Olsen)

Roadcuts expose layers of rock that have been hidden from view for millions of years. Each layer, or stratum, tells a story of what the environment was like when that layer was deposited. By studying these layers, geologists can reconstruct a timeline of events that shaped the region. For example, they can identify periods of volcanic activity, times when the area was submerged under an ancient ocean, or epochs when massive glaciers were carving out the valleys.

California is especially interesting due to its active tectonic setting. It’s not just the San Andreas Fault that captivates geologists; there are numerous lesser-known faults that crisscross the state, and roadcuts can expose these hidden fractures. By studying the composition of rocks along these faults, geologists learn about the nature of past seismic activity and can make predictions about future earthquakes.

The rock composition in California varies widely, offering a rich tapestry of geological history. In the Sierra Nevada, granite roadcuts tell of a time when massive chambers of magma slowly cooled and crystallized deep beneath the Earth’s surface. Elsewhere, roadcuts through sedimentary rocks like sandstone and shale may contain fossils, giving clues about the life forms that once inhabited the region.

The San Gabriel Mountains consist of granite rocks of several kinds and a variety of other crystalline rocks, mainly schists, some of which were originally shales and sandstones but have been altered (metamorphosed) by great igneous intrusions and compression. (Photo: Erik Olsen)

These man-made artifacts also reveal the forces that have shaped California’s diverse landscapes. In roadcuts, geologists might find evidence of powerful geological processes such as metamorphism, where existing rock types are transformed into new types due to high pressure and temperature conditions. For instance, the presence of metamorphic rocks like schist and gneiss can indicate ancient collision zones where Earth’s tectonic plates have crashed together.

The value of California roadcuts is wonderfully illustrated in John McPhee’s “Assembling California.” The book is an excellent narrative that weaves the tale of California’s complex geology with the lives of the geologists who study it. Eldridge Moores, a late prominent geologist from the University of California, Davis (Moores died in 2018), played a significant role in deciphering the geological history of the region, particularly through his fieldwork involving roadcuts.

Roadcut in San Gabriel mountains. (Photo: Erik Olsen)

At the time Eldridge Moores entered the field, the theory of plate tectonics was only beginning to gain traction. In the early 1960s, the idea that continents drifted and that vast slabs of the Earth’s crust moved over the mantle was still controversial, met with skepticism by many geologists trained in older, fixist models. Moores, however, embraced the theory early, recognizing in it an explanation for the chaotic structures he saw in California’s mountain belts. As a young researcher, he studied the Troodos ophiolite in Cyprus, an exposed section of ancient oceanic crust, and realized that similar rock assemblages—serpentinized peridotites, deep-sea sediments, and basaltic lavas—were scattered across California.

“It was a very exciting time. I still get goosebumps even talking about it,” Moores told KQED in 2017. “A turning point, I think it was, in the plate tectonic revolution, that was the watershed of geology.”

With plate tectonics as a guiding framework, Moores understood that these rocks were remnants of vanished oceans, relics of seafloor that had been uplifted and accreted onto the edge of North America. His work helped reveal that much of California had arrived in pieces, a geological patchwork of island arcs, deep-sea basins, and continental fragments welded together by subduction. While others were still debating the validity of plate tectonics, Moores was already applying it, using it to decode the assembly of an entire state.

*Eldridge Moores at the Cordelia fault.* (Photo: UC Davis)

Moores was renowned for his work on ophiolites, sections of the ocean floor that have been thrust up onto the continent. One of his notable discoveries was the identification of ophiolite sequences in the roadcuts along the highways of the Sierra Nevada. These discoveries were crucial in understanding the ancient tectonic movements that shaped western North America.

Through roadcuts, Moores and his colleagues were able to observe and study the juxtaposition of different rock types, providing further evidence for the theory of plate tectonics. They could literally walk along the cuts and see how different terranes—large packets of rock with a distinct geological history—were stitched together like a geological quilt, offering insight into the past locations of tectonic plates.

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“Nature is messy,” Moores once told McPhee. “Don’t expect it to be uniform and consistent.”

There are thousands of roadcuts across California, each exposing a fragment of the state’s chaotic geology. The Palmdale Roadcut, a striking geological feature along the San Andreas Fault, has been an invaluable resource for geologists studying the dynamics of this infamous fault line. This natural cut exposes a cross-section of the earth, revealing layers of rock and sediment that have been shifted and shaped by seismic activity over millions of years. The rock here is a chaotic mélange—fault gouge, shattered granite, and twisted layers of sedimentary rock that have been pulverized and ground together by the relentless motion of the Pacific and North American plates. By analyzing these layers, geologists can better understand the history and behavior of the San Andreas Fault, including the patterns of past earthquakes and the movements of tectonic plates. This, in turn, contributes significantly to the broader understanding of seismic risks and aids in preparing for future seismic events.

The Palmdale Road Cut on Hwy 14 in Southern California is a 90-foot slice through swirling sediments that have spent millions of years being squeezed and twisted by the San Andreas fault. Some say that this view of the fault is one of the best in all of California.
(Photo: Erik Olsen)

Another geologist, Garniss Curtis, used California roadcuts to study volcanic rocks and their embedded minerals, which allowed for the dating of geologic events with greater precision. His work on the potassium-argon dating method turned roadcuts into time machines, where the age of rocks could be determined with the help of exposed minerals.

One of California’s most well-known roadcuts, the Charlie Brown Outcrop (map), is a favorite among geologists. Located along Highway 178 near the Nevada border, it has been highlighted by geology teacher Garry Hayes, author of the acclaimed Geotripper blog. Hayes says of the roadcut (also known as the Shoshone Roadcut):

“There are really three stories told in this exposure, that of distant ash eruptions, a violent eruption close by, and earthquakes with associated mountain-building.”

Charlie Brown outcrop along highway 178 in California. (Google Maps)

These geologists, among others, have used roadcuts as a means to peel back the layers of time, revealing the processes that have operated to create the state’s diverse geologic scenery. Roadcuts have provided the evidence for groundbreaking theories and have been instrumental in mapping the geological evolution of California. The work of these scientists exemplifies the roadcut’s role as a natural laboratory, a place where Earth’s geologic history is on full display for those who know how to read the rocks.

Moreover, roadcuts are crucial for educating the next generation of geologists. They serve as natural laboratories where students can practice identifying rock types, deciphering the sequence of geological events, and understanding the dynamic forces that continue to shape the Earth.

Roadcuts in California, those slices through hills and mountainsides made during the construction of roads, are like open books to geologists. They reveal the intricate and often dramatic geological history of the state. (Photo: Erik Olsen)

In Assembling California, McPhee remarked that “geologists are like dermatologists: they study, for the most part, the outermost two per cent of the earth. They crawl around like fleas on the world’s tough hide, exploring every wrinkle and crease, and try to figure out what makes the animal move.”

Manmade creations like roadcuts greatly assist geologists in their work. In essence, roadcuts are not just incidental byproducts of infrastructure development; they are key to understanding California’s complex geological evolution. They tell stories of ancient environments, tectonic upheavals, and the slow but inexorable forces that continue to mold the landscape. For geologists in California, the roadcut is a portal into the deep past, offering a tangible connection to the processes that have made the state what it is today.

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