In early 1934, Southern California experienced one of the most tragic and devastating natural disasters in its history as a populated region: the Los Angeles flood of 1934. This flood, largely forgotten today outside of the areas directly affected, struck La Crescenta, Montrose, and other foothill communities with devastating force, reshaping not just the landscape but the way California approached flood management and disaster preparedness. It was one of the deadliest floods in Los Angeles history.
The catastrophe took shape in early January after a period of intense rainfall, likely the product of an atmospheric river, a weather phenomenon that can deliver extreme, concentrated rainfall over a short period. In this case, a series of storms in early 1934 carried moisture from the Pacific Ocean directly into Southern California. The storms brought unusually heavy rain to the region, especially to the steep, fire-scarred San Gabriel Mountains.
Nearly 12 inches of rain poured over the foothills in a span of a few days, saturating the steep slopes of the San Gabriel Mountains. The natural landscape was already vulnerable, scarred by wildfires that had burned through the mountains in recent years, leaving slopes exposed and unable to hold the sudden deluge. At this time, the practice of fire suppression had only just begun, meaning that the region’s dry, chaparral-covered mountainsides were naturally prone to burns, which often created perfect conditions for flash floods in winter. Once the rainfall reached a critical level, water, mud, and debris barreled down the mountains, channeled by steep canyons that funneled the destructive flow toward the communities below.
A worker digs out a car and the remains of a home on Glenada Ave. in Montrose. (LA Times)
La Crescenta and Montrose were hit hardest, with residents astonished by walls of mud and rock rushing down their streets. Homes were swept from their foundations; trees, rocks, and debris clogged roadways, and massive boulders tumbled down, crushing cars, smashing into homes and rolling into the middle of once-busy streets. The disaster destroyed over 400 homes and claimed dozens of lives, and numerous people were injured. The streets were piled with silt and debris, several feet thick, which made rescue efforts nearly impossible at first. Additionally, infrastructure like power lines and bridges was obliterated, leaving the communities isolated and in darkness. The floodwaters, swollen with debris, rushed into homes, sweeping families out into the chaos, while cars and buildings alike were left buried or carried off entirely.
Believing it to be a secure shelter for the night, a dozen people took refuge in the local American Legion Post 288. Tragically, the building lay squarely in the path of a powerful debris flow that swept down from Pickens Canyon. The force of the flood shattered the hall’s walls, filling it with thick mud that buried everyone inside before surging on its destructive path. Today, a modest memorial honors those lost to the 1934 flood, overlooking the site of the former hall, which has since been converted into part of the flood control infrastructure.
American Legion Hall damaged by flood and mudslide, La Crescenta-Montrose, 1934 (LA Times)
In the aftermath of the tragedy, local and state governments were forced to confront the region’s vulnerability to such floods. At that time, Los Angeles was in the throes of rapid expansion, with more people moving to suburban areas near the San Gabriel Mountains. The flood, along with an even more destructive one in 1938, firmly swayed public opinion toward a comprehensive flood control strategy. The concrete channels that cut through Los Angeles today are part of this system, designed to swiftly carry water past the city and out to the ocean. brought a clear message: these communities needed better protection. As a result, California embarked on an ambitious flood control plan that would shape Los Angeles County’s infrastructure for decades. Engineers and city planners constructed a network of dams, basins, and concrete channels, including structures like the Big Tujunga Dam, to control water flow from the mountains. The Los Angeles River was channeled and paved, transforming it from a meandering, unpredictable river into the hard-lined, brutalist urban waterway we see today. The Arroyo Seco and other channels were also developed as part of this system to divert stormwater, preventing future flood damage in surrounding communities.
People survey the damage to their cars and roads in the aftermath of the flood. (LA Times)
Over the years, this engineering effort proved largely effective in preventing a recurrence of the devastation that struck La Crescenta and Montrose. However, modern critics argue that these concrete channels, while functional, have disconnected Los Angeles from its natural water systems, affecting both wildlife habitats and the local ecosystem. In recent years, the focus has shifted toward exploring more sustainable flood management techniques, with an eye toward revitalizing some of the natural waterways. This includes restoring parts of the Los Angeles River with green spaces, enhancing biodiversity, and creating flood basins that can handle overflow while supporting ecosystems. In this way, the 1934 flood has left a long-lasting impact, as it continues to influence flood control policies and urban planning in the region.
Mud, rocks, and wrecked cars littered Montrose Avenue in Montrose after the New Year’s flooding. (LA Times)
Today, with climate change bringing more extreme weather, Los Angeles is once again reflecting on its flood infrastructure. The LA River Restoration Master Plan is an ambitious project aimed at transforming the Los Angeles River from a concrete flood channel back into a vibrant, naturalized waterway that serves as a green space for local communities. The plan envisions revitalizing the river’s ecosystems, improving water quality, and creating public parks, walking trails, and recreation areas along the river’s 51-mile stretch. By reconnecting neighborhoods and restoring wildlife habitats, it seeks to bring nature back into the urban core. However, the plan comes with significant challenges, including an estimated cost of up to $1.5 billion and complex engineering demands to ensure flood safety while restoring the river’s natural flow and ecology.
Rendering of a section of the LA River part of the Los Angeles River Revitalization Master Plan (Wenk Associates)
The 1934 flood serves as a sobering reminder of the dangers posed by sudden, intense rainfall in fire-prone mountainous regions. As California experiences more intense wildfire seasons, the cycle of fire followed by flood continues to be a significant threat. The legacy of the Los Angeles flood of 1934 underscores the delicate balance required in managing natural landscapes and urban expansion and remains a critical part of understanding how communities can—and must—adapt to an unpredictable climate future.
From Battlefront to Atomic Legacy: The Journey of the USS Independence to Its Final Resting Place off Northern California
The U.S. Navy light aircraft carrier USS Independence (CVL-22) in San Francisco Bay (USA) on 15 July 1943. Note that she still carries Douglas SBD Dauntless dive bombers. Before entering combat the air group would only consist of Grumman F6F Hellcat fighters and TBF Avenger torpedo bombers. (Wikipedia)
The waters off California’s coast are scattered with relics of wartime history, each telling its own story of conflict and survival. Among these wrecks is the USS Independence, a WWII aircraft carrier whose journey took it from the heights of naval warfare to the depths of nuclear experimentation. Today, it lies as an underwater monument to both wartime heroics and the nascent atomic age.
Converted from the hull of a Cleveland-class light cruiser, the USS Independence was built by the New York Shipbuilding Corporation and commissioned in January 1943. She quickly became a key player in the Pacific Theater. She took part in early attacks on Rabaul and Tarawa before being torpedoed by Japanese aircraft, necessitating repairs in San Francisco from January to July 1944. After these repairs, the Independence launched strikes against targets in Luzon and Okinawa, and was part of the carrier group that sank remnants of the Japanese Mobile Fleet during the Battle of Leyte Gulf, as well as several other Japanese ships in the Surigao Strait.
It took part in pivotal operations such as those at Tarawa, Kwajalein, and the Marianas, contributing significantly to the success of Allied forces. Until the surrender of Japan, she was assigned to strike duties against targets in the Philippines and Japan, and she completed her operational duty off the coast of Japan, supporting occupation forces until being assigned to be a part of Operation Magic Carpet, an operation by the U.S. War Shipping Administration to repatriate over eight million American military personnel from the European, Pacific, and Asian theaters. The ship’s role in supporting invasions and launching strikes helped secure a strategic advantage in the Pacific, establishing the Independence as an integral part of the U.S. Navy’s war effort.
Aerial view of ex-USS Independence at anchor in San Francisco Bay, California, January 1951. There is visible damage from the atomic bomb tests at Bikini Atoll. (San Francisco Maritime National Historical Park)
After WWII ended, the Independence was not destined for a peaceful decommissioning like many of her sister ships. Instead, it was selected for an unprecedented mission: to test the effects of nuclear explosions on naval vessels. In 1946, the Independence became part of Operation Crossroads at Bikini Atoll, a series of nuclear tests aimed at understanding the power of atomic bombs. Positioned near ground zero for the “Able” and “Baker” detonations, the carrier survived but sustained heavy radioactive contamination. Towed back to the United States, it became the subject of further scientific study, focusing on radiation’s effects on naval ships.
Thermonuclear blast part of Operation Crossroads
Ultimately, in 1951, the Navy decided to scuttle the Independence off the coast of California, within what is now the Monterey Bay National Marine Sanctuary and near the Farallon Islands. The ship was intentionally sunk in deep waters, where it would remain hidden for over sixty years. In 2015, researchers from NOAA, in partnership with Boeing and other organizations, used advanced sonar technology to locate the wreck. Lying nearly 2,600 feet below the surface and approximately 30 miles off the coast of San Francisco, the Independence was found in remarkably good condition. The cold, dark waters of the Pacific had preserved much of its hull and flight deck, leaving a ghostly relic that continued to capture the imagination of historians and marine scientists alike.
The U.S. Navy light aircraft carrier USS Independence (CVL-22) afire aft, soon after the atomic bomb air burst test “Able” at Bikini Atoll on 1 July 1946. (US NAVY)
In 2016, the exploration vessel Nautilus, operated by the Ocean Exploration Trust, conducted detailed dives to study the wreck. The exploration utilized remotely operated vehicles (ROVs), equipped with high-definition cameras and scientific tools, to capture extensive footage and data. The mission was led by a multidisciplinary team of researchers, including marine biologists, archaeologists, and oceanographers from NOAA and the Ocean Exploration Trust, highlighting the collaborative effort necessary for such an in-depth underwater expedition. Remotely operated vehicles (ROVs) provided stunning footage of the carrier, revealing aircraft remnants on the deck and bomb casings that hinted at its atomic test history.
Part of an aircraft on the USS Independence seen during the NOAA / Nautilus expedition off the coast of California. (NOAA)
Despite its radioactive past, the wreck had transformed into a thriving artificial reef. Marine life, including fish, crustaceans, and corals, had made the irradiated structure their home, providing researchers with a valuable opportunity to study how marine ecosystems adapt to and flourish on man-made, contaminated structures. Among the biological discoveries, researchers noted a variety of resilient species that had colonized the wreck, including deep-sea corals that appeared to be unaffected by the radiation levels. Additionally, biologists observed that some fish populations had become more abundant due to the complex structure offered by the wreck, which provided shelter and new breeding grounds. This adaptation indicates that artificial reefs—even those with a history of contamination—can become crucial havens for marine biodiversity. Studies also identified microorganisms capable of thriving in irradiated environments, which could help inform future research into bioremediation and the impact of radiation on biological processes. These findings collectively reveal the remarkable ability of marine life to adapt, demonstrating resilience even in challenging conditions shaped by human activities.
The shipwreck site of the former aircraft carrier, Independence, is located in the northern region of Monterey Bay National Marine Sanctuary.
The ship’s resting place has also become an important case study for understanding the long-term effects of radiation in marine environments. Researchers have found that despite the contamination from the atomic tests, the marine life around the Independence has flourished, suggesting a remarkable resilience in the face of human-induced challenges. This has provided invaluable information on how marine ecosystems can adapt and endure even in seemingly inhospitable conditions, shedding light on ecological processes that could inform conservation efforts in other marine environments.
Guns on the USS Independence off the coast of California. An array of corals sponges and fish life are a remarkable testament to manmade reefs to attract sea life (NOAA)
The exploration of the Independence also stands as a technological achievement. The discovery and study of the wreck required advanced sonar imaging and remotely operated vehicle technology, showcasing the capabilities of modern marine archaeology. The collaboration between NOAA, the Ocean Exploration Trust, and other organizations has underscored the importance of interdisciplinary approaches in uncovering and preserving underwater cultural heritage.
Ultimately, the USS Independence is more than just a sunken warship—it is a chapter of American history frozen in time beneath the waves of the Pacific. As a subject of study, it bridges past conflicts with modern scientific inquiry, providing a rich narrative that combines warfare, innovation, and nature’s adaptability. Its story continues to evolve as researchers uncover more about the vessel and the surrounding ecosystem, making it not only a relic of history but also a symbol of discovery and resilience.
Update (February 2025): The Ivanpah Solar Electric Generating System, once a milestone in renewable energy, now faces possible closure. Pacific Gas & Electric has agreed to terminate its contracts, citing the higher cost of Ivanpah’s solar-thermal technology compared to photovoltaics. If approved, two of the plant’s three units could shut down by 2026. Southern California Edison is also considering a contract buyout, adding to uncertainty. Environmental concerns, including bird and tortoise deaths from intense solar radiation, have further complicated Ivanpah’s legacy, reflecting the challenges of large-scale clean energy projects.
In the heart of the Mojave Desert, a glittering sea of mirrors sprawls across 3,500 acres, harnessing the relentless desert sun to power homes and businesses across California. As you drive to or from Las Vegas to the West, the facility rises from the desert, resembling an alien spaceport in the distance. From the air, passengers on flights over the desert can easily spot the plant, with its three towering structures gleaming nearly as brilliantly as the sun.
This ambitious undertaking, known as the Ivanpah Solar Electric Generating System, stands as one of the largest concentrated solar power (CSP) plants in the world. Since its completion in 2014, Ivanpah has been celebrated as a major milestone in renewable energy innovation, while also facing considerable scrutiny and challenges.
The idea behind Ivanpah was born from the vision of BrightSource Energy, led by Arnold Goldman, who was an early pioneer of solar thermal technology. Goldman had previously been involved with Luz International, a company that attempted similar solar ventures in the 1980s. Those early projects struggled due to high costs and limited efficiency, eventually falling victim to the market forces of low fossil fuel prices and a lack of policy support. But by the mid-2000s, the winds had shifted. California, driven by its Renewable Portfolio Standard (RPS), began pushing aggressively for renewable energy sources, setting ambitious targets that mandated utilities procure a large percentage of their electricity from clean sources. This provided fertile ground for a revived effort in concentrated solar power.
Ivanpah Solar Power Facility, a glittering sea of mirrors sprawls across 3,500 acres, harnessing the relentless desert sun to power homes and businesses across California. (Erik Olsen)
With significant financial backing from NRG Energy, Google—which has a strong interest in promoting renewable energy as part of its sustainability goals—and the U.S. Department of Energy (which provided a $1.6 billion loan guarantee), the Ivanpah project broke ground in 2010 and began operation in 2014. By its completion, it had become a landmark renewable energy installation—a bold attempt to demonstrate the viability of CSP technology at scale, with a capacity of 392 megawatts (MW), enough to power around 140,000 homes at peak production.
Ivanpah’s CSP technology differs significantly from the more common photovoltaic (PV) solar panels that typically sprawl across rooftops and solar farms. Instead of directly converting sunlight into electricity, Ivanpah employs a central tower system that uses concentrated solar power to generate steam. The facility harnesses the reflections of 173,500 heliostats (large mirrors) spread across the desert floor, each of which tracks the sun throughout the day using computer algorithms, reflecting sunlight onto a central receiver at the top of Ivanpah’s three 450-foot towers.
Photovoltaic solar array in the Mojave Desert in California (Erik Olsen)
Inside these towers, the intense, concentrated sunlight heats water to temperatures of over 1,000°F (537°C). This heat turns water into steam, which drives turbines to generate electricity. This process—turning solar energy into heat, then into steam, and finally into electricity—requires multiple stages of energy conversion, introducing inefficiencies along the way. While innovative, these conversions come with inherent energy losses that ultimately affect overall efficiency. Some of these inefficiencies and energy losses were unanticipated, demonstrating the complexities of scaling concentrated solar power to this level.
The theoretical efficiency of CSP systems like Ivanpah is generally around 15-20%. By comparison, modern PV panels convert sunlight directly into electricity, achieving efficiencies of 15-22%, with some high-end models exceeding 25%. The direct conversion of sunlight by PV systems avoids the multiple stages of transformation needed by CSP, making PV generally more efficient and cost-effective. That is not to say the project was not an unworthwhile effort, just that it has not yet met the early expectations for the technology.
Ivanpah Solar Power Facility from an airplane. (Erik Olsen)
While Ivanpah was a leap forward in solar technology, it has faced several challenges, both technical and environmental. One of the first issues arose in the initial years of operation: the plant produced less electricity than anticipated, often falling short of its projected targets. This shortfall was attributed to a combination of technical complications, lower-than-expected solar irradiance, and operational adjustments as engineers sought to optimize the plant’s complex systems.
In addition, Ivanpah relies on natural gas to preheat its boilers in the early morning or during cloudy weather, ensuring the turbines are ready to operate as soon as the sun provides enough energy. This auxiliary use of natural gas has sparked criticism, with some questioning whether Ivanpah can truly be considered a clean, renewable energy source. While the natural gas usage is minimal relative to the plant’s total output, it highlights a practical limitation of CSP systems, which need to overcome the intermittent nature of sunlight.
Environmental impacts have also drawn attention. Ivanpah’s vast array of mirrors produces a phenomenon known as solar flux, a concentrated field of heat that can reach temperatures high enough to injure or kill birds flying through it. Dubbed ‘streamers,’ because of the smoke that comes from their wings when they burn in midair, birds that enter this concentrated beam often die. (Here’s a video about it.) A report from the California Energy Commission refers to what they call a “megatrap,” where birds are drawn to insects that are attracted to the intense light emitted from the towers. This unintended effect on wildlife has been a significant concern for conservation groups, prompting Ivanpah to work on mitigation measures, including testing visual deterrents to keep birds away.
A burned MacGillivray’s Warbler found at the Ivanpah solar plant during a visit by U.S. Fish and Wildlife Service in October 2013. U.S. Fish and Wildlife Service/AP Photo
Moreover, the sheer size of Ivanpah, covering a significant area of desert land, has raised concerns about the impact on local ecosystems. The Mojave Desert is a delicate environment, and constructing such a large facility inevitably affected the flora and fauna, prompting debates about whether renewable energy projects should be balanced with efforts to preserve pristine habitats.
Ivanpah is just one of several large-scale CSP projects around the globe. Another notable example is the Noor Ouarzazate Solar Complex in Morocco, which is one of the largest CSP installations in the world. The Noor Complex uses both parabolic trough and solar tower technologies and, crucially, incorporates molten salt to store heat, allowing it to generate electricity even after the sun has set. The use of molten salt offers several advantages over water-based systems like Ivanpah. Molten salt can retain heat for longer periods, enabling the plant to continue generating power during periods of low sunlight or even after sunset, which greatly improves grid reliability and helps balance energy supply with demand.
The Crescent Dunes Solar Energy Project, once a symbol of cutting-edge solar technology with its 640-foot tower and field of over 10,000 mirrors, now stands as a cautionary tale of ambitious renewable energy efforts. Despite its initial promise, the project was plagued by technical issues and ultimately failed to meet its energy production goals, leading to its closure. (U.S. Department of Energy)
Similarly, the Crescent Dunes project in Nevada was another attempt to utilize molten salt for energy storage. It initially showed promise but struggled with technical setbacks and eventually ceased operation in 2019 due to persistent issues with the molten salt storage system and failure to meet performance expectations. The technology, although innovative, struggled with high maintenance costs, particularly with the heliostat mirrors and salt storage tanks. The company behind Crescent Dunes, SolarReserve, went bankrupt after being sued by NV Energy for failing to meet its contractual obligations.
Despite these setbacks, the project has not been fully decommissioned. ACS Cobra, the Spanish firm involved in its construction, now operates the plant at reduced capacity, mainly delivering energy during peak demand at night. Although Crescent Dunes has never reached its full potential, it continues to produce some electricity for Nevada’s grid, albeit far below the originally planned levels.
Crescent Dunes underscored the challenges associated with large-scale CSP projects, particularly the difficulty of balancing complexity, maintenance, and operational costs. However, the use of molten salt in Crescent Dunes demonstrated the significant potential for improving CSP efficiency through effective thermal storage, highlighting a critical advantage over water-based systems like Ivanpah that lack extensive storage capabilities.
While CSP holds the advantage of potential energy storage—something PV cannot inherently achieve without additional batteries—PV technology has seen a steep decline in cost and significant improvements in efficiency over the past decade. This rapid evolution has made PV panels more attractive, leading to widespread adoption across both utility-scale and residential projects. Hybrid projects, like Phase IV of the Mohammed bin Rashid Al Maktoum Solar Park in Dubai, are now combining PV and CSP technologies to maximize efficiency and output, utilizing each technology’s strengths.
Ivanpah remains operational, continuing to contribute renewable energy to California’s grid.
Photovoltaic solar array in the Mojave Desert in California (Erik Olsen)
Governor Gavin Newsom has commented on the importance of renewable projects like Ivanpah in meeting California’s ambitious clean energy goals. Newsom has praised Ivanpah as a vital component of the state’s effort to transition away from fossil fuels, emphasizing the need for innovative projects to meet California’s target of achieving 100% renewable energy by 2045. He has highlighted the symbolic value of Ivanpah, not only as a source of clean energy but as a testament to California’s leadership in renewable technology and environmental stewardship. Its story is one of both ambition and caution, highlighting the promise of concentrated solar power as well as its practical and environmental limitations. In many ways, Ivanpah serves as a testbed for CSP technology, providing valuable insights into the challenges of scaling such systems to utility-level production. It has also sparked discussions on the role of CSP compared to other forms of renewable energy, especially as battery technology advances to address PV’s storage challenges.
While CSP is unlikely to overtake PV in terms of widespread adoption due to its complexity and cost, it still has a role to play, particularly in regions with intense sunlight and a need for energy storage. The lessons learned at Ivanpah—both the successes and the setbacks—will inform the next generation of solar projects, driving innovation and helping policymakers, engineers, and investors make more informed decisions about the future of renewable energy infrastructure.
Mohammed bin Rashid Al Maktoum Solar Park (Government of Dubai)
California’s solar and renewable energy installations have seen remarkable success in recent years, as the state continues to push toward its ambitious goal of 100% clean electricity by 2045. In 2024, California achieved several milestones that highlight the effectiveness of its clean energy initiatives. For example, the state has more than 35,000 MW of renewable energy capacity already serving the grid, with 16,000 MW added just since 2020. A key component of this growth is the rapid expansion of battery storage, which has become essential for balancing the grid, especially during peak demand times when solar power diminishes in the evening. In 2024 alone, battery storage capacity grew by over 3,000 MW, bringing the total to more than 13,000 MW—a 30% increase in just six months
In addition to storage, new solar projects like the Blythe Solar Power Project, which generates 485 MW of photovoltaic power and adds 387 MW of battery storage, are powering over 145,000 homes, further demonstrating California’s leadership in clean energy development. This continued investment not only strengthens the grid but also ensures resilience during extreme weather events, which have become more frequent due to climate change.
Despite these successes, California still has a long way to go. The state will need to bring an additional 148,000 MW of renewable resources online by 2045 to fully meet its goals. However, with the state’s rapid advancements in storage technology, solar capacity, and governmental support, California is well on its way to achieving a cleaner, more sustainable energy future.
Google arranged the mirrors at Ivanpah to create a tribute to Margaret Hamilton, the pioneering computer scientist who led the software engineering efforts for the Apollo space missions. (Google)
Beyond its role in renewable energy, Ivanpah has also found itself at the intersection of technology and art. One notable example is when Google arranged the mirrors at Ivanpah to create a tribute to Margaret Hamilton, the pioneering computer scientist who led the software engineering efforts for the Apollo space missions. This artistic alignment of mirrors highlighted Ivanpah’s versatility—not just as an engineering marvel for energy generation but also as a symbol of human achievement. The intricate choreography of heliostats to form an image visible from above served as a powerful visual homage, merging art, science, and technology in a striking way. Such projects have helped broaden the cultural significance of Ivanpah, presenting it not only as a source of renewable energy but also as an inspirational platform that celebrates human creativity and accomplishment.
The next time you’re driving to Vegas and spot the three massive, sun-like objects glowing in the desert, give a thought to the immense power—and challenges—of harnessing the sun’s energy in such a dramatic way.
Ansel Adams, with his iconic black-and-white photographs of Yosemite and the Sierra Nevada, likely never realized that his lens was capturing not just breathtaking landscapes but one of geology’s most fascinating phenomena—the Sierra Batholith, a colossal formation of granite that lies at the heart of the mountains he immortalized. The Sierra Batholith is a massive granite body that reveals the tale of ancient volcanic activity in California, showcasing nature and time as master artists, and the slow tectonic forces that have shaped the Earth’s crust over millions of years.
Discussing the Sierra batholith, the writer John McPhee wrote: “It lies inside the Sierra like a big zeppelin. Geologists in their field boots mapping outcrops may not have been able to find a bottom, but geophysicists can, or think they can, and they say it is six miles down. If so, the batholith weighs a quadrillion tons, and its volume is at least a hundred and fifty thousand cubic miles.”
The Sierra Batholith is unique because it represents a massive, exposed section of the Earth’s continental crust formed deep underground during the Mesozoic era, between 85 and 220 million years ago. Unlike typical mountain ranges that form through surface processes, the Sierra Batholith was created as molten rock, or magma, cooled and solidified far beneath the Earth’s surface.
A batholith is a gargantuan underground rock formation made up mostly of intrusive igneous rock, predominantly granite.” Intrusive” in this context doesn’t mean the rock is barging into conversations—it refers to rock that formed beneath the Earth’s surface as molten magma slowly cooled and solidified. The Sierra Nevada batholith is a titan among batholiths, covering an area of about 40,000 square kilometers (16,000 sq. miles).
How did this underground monolith come into being? Picture the Earth’s crust as a sort of geological lasagna, consisting of multiple layers of rock. When the Pacific Plate and the North American Plate crashed into one another—intense pressure and heat accumulated deep within the Earth. The result is the formation of magma, which then cooled and solidified slowly below the Earth’s crust. The slow cooling allowed minerals to crystallize, creating a texture in the rock that’s coarse and beautifully patterned—not unlike granite countertops for your kitchen, but on a monumental scale.
The Sierra Nevada Batholith was only revealed after vertical miles of Earth’s crust above it eroded away. Stretching from just north of Lake Tahoe to Tehachapi Pass, this massive formation resembles an air mattress—450 miles long, 60 miles wide, and about eight to nine miles thick, with six miles still buried underground and two to three miles towering above the surrounding landscape. The sheer size, scale, and immense mass are awe-inspiring—and it’s all right here in California.
This creation process was far from uniform—the batholith is actually not a single mass, per se, but a cluster of blobs of molten rock fused at the edges. These blobs, called plutons, are clustered together like cobblestones in a street or the uneven domes of a bubble wrap sheet. What we now see are the rounded tops of about 20 oval-shaped plutons, each around 10 by 20 miles in size. Chemically, each blob varies slightly. Granite, made mostly of silica, which forms 60 to 80 percent of its mass, gets its whitish hue from silica, with black flecks of feldspar and hornblende, sometimes tinged with reddish iron oxide. The slower the cooling, the more time quartz crystals had to form.
One of the largest and youngest plutons in the Sierra is called the Whitney Intrusive Suite, and it is the foundation of the nation’s tallest peak outside of Alaska, Mt. Whitney.
A geologic map of Yosemite National Park showing the many intrusions that make up this part of the Sierra Nevada Batholith.
Natural forces like wind, water, and glaciers have gradually eroded the Earth’s surface, exposing the underlying granite. Imagine the work of an infinitely patient sculptor, slowly chipping away at a block of marble year after year, century after century. Except here, the sculptor is Mother Nature, and the time frame is geological, spanning epochs rather than mere decades or centuries.
One fascinating facet of this story is how glaciers have been among the most dramatic artists in nature’s magnificent art gallery. Their slow, relentless movement sculpted features like Yosemite Valley, one of the most breathtaking landscapes on Earth.
Half Dome in Yosemite, a granite giant of the Sierra Batholith, showcases millions of years of cooling magma and erosion. (Erik Olsen)
But the Sierra Nevada batholith isn’t just a stationary slab of rock—it’s also a dynamic part of California’s ecosystem. The granite affects the way water moves or stagnates in the region, influencing local hydrology and, by extension, water supply. When the snow in the Sierra Nevada mountains melts, it feeds rivers and lakes, many of which are essential to California’s agricultural and urban areas. Imagine the batholith as a silent but vital cog in the wheel of California’s complex water system.
One excellent resource to learn more about the Sierra and the Sierra batholith is Kim Stanley Robinson‘s The High Sierra: A Love Story. The book is an evocative blend of memoir, natural history, and environmental meditation, centered around the Sierra Nevada mountains, a region Robinson has deeply cherished for decades. Robinson, widely regarded as one of today’s greatest science fiction writers, has authored numerous books on topics ranging from space exploration to climate change. Yet one of his deepest passions is hiking in the Sierra.
Half Dome, carved from the granite of the Sierra Batholith, offers a glimpse into Earth’s deep history, where ancient magma chambers solidified beneath the surface and were gradually revealed through uplift and erosion. (Erik Olsen)
In the book, he explores the geologic grandeur, ecological richness, and personal significance of this mountain range, offering readers a vivid portrayal of its granite peaks, alpine meadows, and glacial valleys. Robinson intertwines his own hiking experiences with reflections on the Sierra’s geological formation, the indigenous histories of the land, and the environmental challenges it faces today. His narrative is as much an ode to the beauty and solitude of the Sierra as it is a call for greater environmental stewardship, showcasing his talent for combining science with a profound emotional connection to the natural world. (If you haven’t yet read one of his books, you should. Start with Red Mars.)
Sierra Nevada from Lone Pine (Erik Olsen)
If you’re the adventurous type with a penchant for rock climbing or hiking, the Sierra Nevada batholith serves as both your playground and your classroom. Whether you’re scaling the granite walls of El Capitan or hiking the trails near Lake Tahoe, you’re traversing a landscape that’s millions of years old. Each crevice, each outcrop, and each boulder tells a tale of geological drama spanning eons.
Last month, a video went viral showing a small pod of dolphins swimming at night off the coast of Newport Beach. Seeing dolphins off Southern California is not particularly unusual, but this was a very special moment. In the video, the dolphins appear to be swimming through liquid light, their torpedo-shaped bodies generating an ethereal blue glow like a scene straight out of Avatar. The phenomenon that causes the blue glow has been known for centuries, but that in no way detracts from its wonder and beauty. The phenomenon is called bioluminescence, and it is one of nature’s most magical and interesting phenomena.
A Caridean shrimp, Parapandalus sp., enveloped in bioluminescent spew emitted during an escape response. (NOAA/OER)
Bioluminescence is the production and emission of light by a living organism, and it is truly one of the great magical properties of nature. At its core, bioluminescence is the way animals can visually sense the world around them. It’s all built on vision, one of the most fascinating and useful senses in the animal kingdom. Seeing is impossible without light, and so it makes sense that in the absence of sunlight, some animals created a way to make their own light.
I have been fascinated by bioluminescence since I was a child growing up near Newport Beach when the occasional nearshore red tide bloom would illuminate the waves like a high tech LED light show. It’s a truly magical experience. I’ve also experienced bioluminescence in various places around the world, including Thailand, Mexico, and Puerto Rico. In fact, 13 years ago, I made the trip to Puerto Rico’s Vieques Island and its world-famous Mosquito Bay, for the sole purpose of seeing the bay in person and swimming and kayaking in its warm, glowing waters (there is a rental outfit there that does tours at night…it’s amazing. Trust me.)
The phenomenon of bioluminescence is surprisingly common in nature. Both terrestrial and sea animals do it, as do plants, insects (for example, fireflies), and fungi. Curiously, no mammals bioluminesce. That we know of, although several species fluoresce, which is when organisms absorb light at one wavelength and emit it at another, often under ultraviolet (UV) light. The platypus is an example. But the ocean is definitely the place that animals and plants bioluminesce the most. Which makes sense because deep in the ocean, there is little or no light. Light is absorbed very quickly in the water, so while on land you might be able to see a single streetlight miles away, after about 800 feet, light largely disappears in the depths of the ocean. I know. I’ve been there.
It’s estimated that nearly 90 percent of the animals living in the open ocean, in waters below 1,500 feet, make their own light. Why they do this is in part a mystery, but scientists are pretty sure they understand the basic reasons animals do it: to eat, to not be eaten, and to mate. In other words, to survive. And to communicate.
Credit: NOAA
The angler fish dangles a lighted lure in front of its face to attract prey. Some squid expel bioluminescent liquid, rather than ink, to confuse their predators. A few shrimp do too. Worms and small crustaceans use bioluminescence to attract mates. When it is attacked, the Atolla jellyfish (Atolla wyvillei) broadcasts a vivid, circular display of bioluminescent light, which scientists believe may be a kind of alarm system. The theory is that the light will attract a larger predator to go after whatever is attacking the jellyfish. While this is still a theory, a 2019 expedition that took the very first images of the giant squid used a fake Atolla jellyfish designed by the scientist Edith Widder to lure the squid into frame. I had the fortune of interviewing Dr. Widder, one of the world’s top experts on bioluminescence, several years ago for the New York Times.
Edith Widder holds a vial of bioluminescent plankton. Credit: Erik Olsen
Making light is clearly beneficial. That’s why, say evolutionary biologists, it appears that bioluminescence has arisen over forty separate times in evolutionary history. The process is called convergent evolution and is the same reason that bats and birds and insects all evolved to fly independently. Clearly, flying confers a major advantage. So does making light.
While the Internet is awash in images of bioluminescent creatures, very often the term is confused with fluorescence (mentioned above). Even reputable science organizations sometimes do this. Bioluminescence is not the same thing as fluorescence. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Many animals like scorpions and coral fluoresce, meaning that they appear to glow a bright otherworldly color when blue light is shone on them. The key idea here is that the animals are not generating their own light, but rather contain cells that reflect light in fluorescence.
Fluorescent (not bioluminescent) scorpion in Baja California, Mexico. Credit: Erik Olsen
So what about the recent explosion of bioluminescence in Southern California? The light we are seeing is made by tiny organisms, type of plankton called dinoflagellates (Lingulodinium polyedra) that occasionally “bloom” off-shore. Often, this is the result of recent storms that bring tons of nutrient-laden runoff into the ocean. The tiny plankton feed on nitrogen and other nutrients that enter the ocean from rivers and streams and city streets. A lot of the nutrients come from California’s vast farms, specifically the fertilizer used to grow California’s fruits and vegetables. With all that “food” coming into the ocean system, the algae rapidly multiply, creating red tides, or vast patches of ocean that turn dark brownish red, the color of pigment in the algae that helps protect it from sunlight. Michael Latz, a scientist at Scripps Institution of Oceanography at UC San Diego, says that the animals use bioluminescence as a predator avoidance behavior.
Sometimes red tides are toxic and can kill animals and make people sick who swim in the ocean. (That does not appear to be the case in California right now). At night, when they are still, the animals can’t be seen. But when the water is disturbed, which adds oxygen into the mix, a chemical reaction takes place in their bodies that causes luciferin (from the Latin lucifer or ‘light-bearer’) to oxidize and becomes catalyzed to make luciferase, which emits photons or particles of light. It’s not understood exactly how or why this happens, but we do know there are many kids of luciferase. In fact, scientists know the genes that create luciferases and have implanted them into organisms like mice, silkworms, and potatoes so that they glow. They’ve made bioluminescent plants, too. An Idaho-based start up called Light Bio, in fact, sells bioluminescent petunias that you can purchase.
Light Bio’s genetically engineered petunias glow green thanks to DNA added from bioluminescent mushrooms. Photo (Light Bio)
Perhaps the most magical thing about bioluminescence is that it doesn’t create heat. Almost all the lights we are familiar with, particularly incandescent light, like that from generic light bubs, generate a tremendous amount of heat. Of course, we have learned how to make this heatless chemical light ourselves, easily experienced when you crack and shake a glow stick, mixing together several chemicals in a process similar to the one animals in the ocean use to create bioluminescent light. But the light from glow sticks is not nearly strong enough to illuminate your back yard. In the last few decades, we’ve learned how to make another kind of light that produces little heat: LEDs. Though the process is very different, the concept is the same: talking a molecule or a material and promoting it to an excited state. Where electricity is used, in the case of LEDs, it’s called electroluminescence, where it’s a chemical reaction it’s chemiluminescence, of which bioluminescence is one form.
Whether you are a religious person or not (I’m not) it’s no coincidence that one of the first things God said was, “Let there be light!” Light and light energy give us plants and animals to eat, and allows us to see. It heats our world, it fuels our cars (oil is really just dead organic material compressed over time, and that organic material would not have existed without sunlight). While some animals deep in the ocean can live without light, most of us cannot. And it’s a rather astounding feat of nature than when there is no light, many of the earth’s creatures have evolved to produce it themselves. If you don’t believe me, just go down to the Southern California shore in the evening when there is a red tide. Leave your flashlight at home. You won’t need it.
Imagine a massive island off the coast of California roughly thrice the size of Maui, a lush and wild place where miniature mammoths once roamed and ancient humans hunted in the shadows of towering trees. This island once existed and it’s called Santarosae, and while it is gone now, it was once a thriving ecosystem, teeming with life. Its story provides a captivating window into the ever-changing natural history of the California coast region.
During the last Ice Age, approximately 20,000 to 25,000 years ago, when sea levels were significantly lower, Santarosae Island was a single, expansive landmass that now comprises most of California’s Channel Islands. As the cooler Pleistocene climate transitioned into the warmer Holocene (the epoch we are in now), the Earth’s oceans heated and expanded. Continental ice sheets and glaciers melted, releasing vast amounts of water and causing sea levels to rise dramatically.
At its peak, Santarosae was massive—four of today’s Channel Islands (San Miguel, Santa Rosa, Santa Cruz, and Anacapa) were all connected into a single landmass. It spanned around 1,500 square miles, making it a significant feature of the Pacific coast landscape. Today, only remnants remain in the form of those four separate islands, but evidence of Santarosae’s ancient past continues to reveal itself to scientists.
Map depicting the reconstructed geography of Santarosae.
Anacapa was the first to break away, around 10,300 to 10,900 years ago, as rising waters gradually submerged the narrow isthmus that once connected it to the rest of Santarosae. This slow disintegration of the super island was witnessed by the humans already inhabiting the region. Having arrived between 12,710 and 13,010 years ago, possibly even earlier, these early settlers likely traveled by boat, following the “kelp highway“—a rich, coastal ecosystem of underwater seaweed forests stretching from northern Japan and Kamchatka, along the southern shores of Beringia, down the Pacific Northwest, and into Baja California. For these early explorers, Santarosae would have appeared as a land of abundant resources.
One of the island’s most captivating features was its population of pygmy mammoths, found exclusively on Santarosae. Standing between 4.5 to 7 feet tall at the shoulder and weighing around 2,000 pounds, these miniaturized versions of mainland Columbian mammoths were about the size of a large horse and evolved to suit their isolated island habitat (see our story on the island biogeography of the Channel Islands). The reasons for their dwarfism stem from a phenomenon called island rule, where species on islands often shrink due to limited resources and isolation, as well as a shortage of predators. Despite their smaller size, these island-dwelling mammoths likely shared many characteristics with their larger relatives, including a similar body shape, short fur, and a large head. These mammoths roamed Santarosae until they disappeared around 13,000 years ago, coinciding with both climate changes and the arrival of humans.
Pygmy Mammoth excavation on the Channel Islands (NPS)
The first discovery of “elephant” remains on Santa Rosa Island was reported in 1873. Over time, additional excavations provided insight into the island’s mammoth population, which gradually became smaller over generations, eventually disappearing at the end of the Pleistocene. Notably, paleontological digs conducted on Santa Rosa Island in 1927 and 1928 unearthed the remains of a new species, Mammuthus exilis. In the 1940s and 1950s, Philip Orr of the Santa Barbara Museum of Natural History recovered further specimens while conducting archaeological and geological work on the island.
Most pygmy mammoth remains have been discovered on Santa Rosa and San Miguel Islands, with fewer finds from Santa Cruz Island and even fewer from San Nicolas Island, which lies outside the Channel Islands National Park.
Santarosae was not just a wilderness for megafauna—it was home to some of the earliest known human settlers in North America. Archaeological discoveries, such as the remains of a 13,000-year-old woman unearthed on Santa Rosa Island, point to a sophisticated maritime culture. These ancient humans, likely ancestors of the Chumash people, navigated the waters around Santarosae in plank canoes, hunting seals, birds, and fish, while gathering plants and shellfish.
Archaeologists excavate a anthropological site at the Channel Islands (NPS)
The island provided ample resources, but it wasn’t isolated from the rest of the world. The people of Santarosae were part of a complex trade network that stretched across the California coast. Evidence of these connections can be seen in the tools and materials found on the island, some of which came from distant sources. As sea levels rose, however, these early inhabitants had to adapt to the shrinking island, eventually migrating to the mainland.
Santarosae’s landscape during the Ice Age was strikingly different from what we see on today’s Channel Islands. Dense forests of pines, oaks, and other vegetation covered much of the island, supporting a rich diversity of life. The island’s topography included hills, valleys, and freshwater sources, offering an ideal environment for both humans and animals. As the climate warmed and sea levels rose, the island’s ecology shifted. Forests retreated, and the landscape began to resemble the wind-swept, scrubby terrain seen on the modern Channel Islands.
Anacapa Island today (Erik Olsen)
The rise in sea levels didn’t just transform the landscape; it also altered the ecosystems. Many of the animals, like the pygmy mammoths, couldn’t survive the changing conditions (or human hunters), while new species adapted to the shrinking landmass. Birds, insects, and plant species began to dominate, and the island ecosystems became more specialized.
Today, the remnants of Santarosae offer an invaluable window into the past. The Channel Islands National Park protects much of the area, and researchers continue to uncover clues about the island’s history. Ongoing archaeological digs and ecological studies on the islands help piece together the story of Santarosae’s people, animals, and landscape.
Tourists now enjoy the natural beauty of the Channel Islands (Erik Olsen)
For those who visit the Channel Islands today, it’s hard to imagine the ancient world of Santarosae—a much larger island teeming with life. But the remnants of this lost island still hold secrets waiting to be uncovered, offering a fascinating glimpse into California’s distant past and a reminder of how the forces of nature continually reshape our world.
Though Santarosae is now submerged, its influence is still a significant part of California’s natural history.
Once teetering on the brink of extinction, the California elephant seal has made an astounding recovery thanks to stringent conservation efforts. But as you’ll read below, their recovery comes with an asterisk. These remarkable creatures, once hunted for their blubber, now thrive along California’s iconic coastline. With their distinctive trunk-like snouts and massive size (They really are huge. I’ve visited the beach near San Simeon several times to photograph them), elephant seals are an incredible sight.
Elephant seals can be seen along the California coast year-round, but specific times are better for different activities. The peak times to observe them are during their breeding season (December to March) and molting season (April to August). During these times, especially from January to March, beaches are filled with males battling for dominance and females giving birth. Outside these seasons, many seals are out at sea, but some can still be spotted during quieter months.
Even considering the animal’s unique appearance, the elephant seal is not just any ordinary seal. Its eating and mating habits are a riveting blend of deep-sea dives in pursuit of prey and intense beachfront battles for dominance during the breeding season.
The species has two main branches: the northern and southern elephant seal. The ones lolling on the California shores belong to the northern branch. Adult males can weigh as much as 2,300 kg (around 5,000 lbs) and can reach up to 14 feet in length. Females, though smaller, play a pivotal role in the seal’s lifecycle.
Baby elephant seal. Photo: NOAA
Elephant seals are deep-sea aficionados, embarking on two major foraging trips each year. To fuel the intense energy demands of mating season, they dive to impressive depths, often around 1,700 feet (518 m), but have been recorded reaching as deep as 5,015 feet (1,529 m). These long dives, sometimes lasting over an hour, help them hunt squids and fishes while also avoiding predators like great white sharks. Only sperm whales dive deeper and longer, showcasing the elephant seal’s mastery of the deep ocean.
The mating habits of the California elephant seal are a spectacle, a mix between The Biggest Loser and UFC. In wintertime, the beaches teem with activity. The males arrive first, establishing territories and preparing to woo potential mates. Skirmishes between rival males are like mixed martial arts battles between extreme heavyweights (ok, I’ll stop). As they fight for dominance and the right to mate, the elephant seal mating ritual can be quite intense. They engage in ferocious body slam battles, using their massive bodies and long proboscises to assert their strength. These skirmishes, often leading to visible scars and wounds, as well as broken bones, are all for the right to mate. The victor, having established his dominance, can then secure a harem of females, while the less dominant males must wait their turn or go without. This intense ritual underscores the seal’s primal drive to ensure its lineage in the face of fierce competition.
Mating battles between elephant seals can be brutal. Photo: NOAA
By the end of the season, successful males might have a harem of up to 50 females. After the mating rituals, females give birth to pups from the previous year’s mating season. The shores become dotted with adorable seal pups, drawing gawkers and photographers from around the globe.
Elephant seal near San Simeon, California. Photo: National Park Service
To catch a glimpse of these magnificent creatures, the California coastline offers several attractive vantage points. Popular spots include Año Nuevo State Park, Point Reyes National Seashore, and Piedras Blancas near San Simeon. Further offshore, the Channel Islands serve as a remote sanctuary for these seals, away from the bustling mainland. Specifically, San Miguel Island and Santa Rosa Island, both part of the Channel Islands National Park, are known hotspots for elephant seal rookeries. These islands provide remote and undisturbed habitats, making them ideal locations for elephant seals to mate, give birth, and molt.
The elephant seal, despite its impressive size and strength, is not exempt from the challenges of predation. Great white sharks and orcas, or killer whales, are the primary natural predators of the elephant seal. While younger seals and females are more vulnerable due to their smaller size, even the massive adult males are not entirely safe. Great white sharks tend to target the seals when they’re in deep waters, ambushing them from below. Orcas, on the other hand, have been known to employ strategic hunting techniques to isolate and attack seals, especially near the shorelines. Several rather astonishing videos have been captured of orcas going after elephant seals in the wild.
The threat of these apex predators plays a significant role in shaping the behaviors and migratory patterns of the elephant seal, as they navigate the perilous waters of the Pacific in search of food and safe breeding grounds.
Elephant seals are known to be migratory, traveling thousands of miles across the Pacific. After their foraging trips, they return to their natal beaches to molt, shedding and replacing their fur and the outer layer of their skin.
Elephant seals on the beach at Piedras Blancas near San Simeon. (Erik Olsen)
However, the journey of the California elephant seal hasn’t always been smooth sailing. Over the past 50 years, there have been significant fluctuations in their population. In the late 19th century, they were nearly hunted to extinction for their blubber, which was valuable in oil production. By the end of the 1800s, only a small colony of fewer than 100 seals (some place the number closer to 25) was believed to exist. But here’s where the story takes a hopeful turn. Thanks to robust conservation efforts and protective legislation, their numbers began to rebound. Today, it’s estimated that the population is around 250,000, a testament to what protective measures can achieve. That said, an unknown proportion of elephant seal populations is always at sea, making accurate assessments of total population size is difficult.
Recent research in 2024 reveals a deeper consequence of this near-extinction event. Genetic analyses show that Northern Elephant seals, while rebounding, still bear “genetic scars.” The dramatic population decline going into the 20th century led to the loss of genetic diversity, raising concerns about inbreeding and potential future vulnerabilities to environmental changes or diseases. However, despite reduced diversity, no immediate health issues have been observed in the species.
Given the many other biological and ecological riches of California (this magazine highlights many of them), the elephant seal owns a precious spot in the pantheon of California’s natural wonders. With their unique lifecycle, impressive size, and dramatic beach battles, elephant seals hold a special place alongside the state’s ancient redwoods, vast deserts, and diverse marine life. Their remarkable comeback from near extinction and the key role they play in coastal ecosystems make them a symbol of resilience and the enduring power of nature to regenerate when given the chance.
