Walter Munk was a Californian Oceanographer Who Changed Our Understanding of the Seas

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Walter Munk, often referred to as the “Einstein of the Oceans,” was one of the most influential oceanographers of the 20th century. Over a career that spanned more than 70 years, Munk fundamentally altered how we think about the oceans, contributing to our understanding of everything from wave prediction during World War II to deep-sea drilling in California. His work at the Scripps Institution of Oceanography in La Jolla, California, was groundbreaking and continues to influence scientific thinking to this day.

Walter Heinrich Munk was born in Vienna, Austria, on October 19, 1917. At 14, he moved to New York, where he later pursued physics at Columbia University. He became a U.S. citizen in 1939 and earned a bachelor’s degree in physics from the California Institute of Technology the same year, followed by a master’s in geophysics in 1940. Munk then attended the Scripps Institution of Oceanography and completed his Ph.D. in oceanography from the University of California in 1947.

Dr. Walter Munk in 1952. (Scripps Institution of Oceanography Archives/UC San Diego Libraries)

In the early 1940s, Munk’s career took a defining turn when the United States entered World War II. At the time, predicting ocean conditions was largely guesswork, and this posed a significant challenge for military operations. Munk, a PhD student at Scripps at the time, was recruited by the U.S. Army to solve a problem that could make or break military strategy—accurate wave prediction for amphibious landings.

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One of his most famous contributions during the war came in 1944, ahead of the Allied invasion of Normandy. Alongside fellow oceanographer Harald Sverdrup, Munk developed a method to predict the size and timing of ocean waves, ensuring that troops could land safely during the D-Day invasion. Using their model, the Allied forces delayed the invasion by one day, a move that proved crucial in reducing casualties and securing the beachhead. This same wave prediction work was used again in the Pacific theater, particularly for landings on islands like Iwo Jima and Eniwetok. Munk’s contributions not only helped win the war but also laid the foundation for modern oceanography. Wave forecasting is now a standard tool for naval operations, shipping, and even recreational surfers.

Landing craft pass supporting warships in the Battle of Eniwetok, 19 February 1944. (U.S. Army)

After the war, Munk returned to Scripps, a place that would remain central to his career. Established in 1903, Scripps had been growing into a major center for oceanographic research, and Munk’s work helped elevate it to new heights. Located in La Jolla, just north of San Diego, Scripps was perfectly positioned on the California coastline to be at the forefront of oceanographic studies. Scripps is one of the premier oceanographic institutions in the world.

During the post-war years, Munk helped pioneer several new areas of research, from the study of tides and currents to the mysteries of the deep sea. California, with its rich marine ecosystems and coastal access, became the perfect laboratory. In La Jolla, Munk studied the Southern California Current and waves that originated across the Pacific, bringing new understanding to local coastal erosion and long-term climate patterns like El Niño. His research had a direct impact on California’s relationship with its coastline, from naval operations to public policy concerning marine environments.

*Walter Munk in 1963 with a tide capsule.* *The capsule was dropped to the seafloor to measure deep-sea tides before such measurements became feasible by satellite.* *Credit Ansel Adams, University of California*

While Munk’s contributions to wave forecasting may be his most widely recognized work, one of his boldest projects came in the 1960s with Project Mohole. It was an ambitious scientific initiative to drill into the Earth’s mantle, the layer beneath the Earth’s crust. The project was named after the Mohorovičić Discontinuity (named after the pioneering Croatian seismologist Andrija Mohorovičić), the boundary between the Earth’s crust and mantle. The boundary is often referred to as the “Moho”. The goal was revolutionary: to retrieve a sample from the Earth’s mantle, a feat never before attempted.

The idea was to drill through the ocean floor, where the Earth’s crust is thinner than on land, and reach the mantle, providing geologists with direct insights into the composition and dynamics of our planet. The project was largely conceived by American geologists and oceanographers, including Munk, who saw this as an opportunity to leapfrog the Soviet Union in the ongoing Cold War race for scientific supremacy.

The *Glomar Challenger*, launched in 1968, was the drill ship for NSF’s Deep Sea Drilling Project. (Public Domain)

California was again the backdrop for this audacious project. The drilling took place off the coast of Guadalupe Island, about 200 miles from the Mexican coast, and Scripps played a key role in organizing and coordinating the scientific work. The project succeeded in drilling deeper into the ocean floor than ever before, reaching 600 feet into the seabed. However, funding issues and technical challenges caused the U.S. Congress to abandon the project before the mantle could be reached. Despite its early end, Project Mohole is considered a precursor to modern deep-sea drilling efforts, and it helped pave the way for initiatives like the Integrated Ocean Drilling Program, which continues to explore the ocean’s depths today. For example, techniques for dynamic positioning for ships at sea were largely developed for the Mohole Project.

Munk’s work was deeply tied to California, a state whose coastlines and oceanography provided a wealth of data and opportunities for study. Scripps itself is perched on a stunning bluff overlooking the Pacific Ocean, a setting that greatly inspired Munk and his colleagues. Throughout his career, Munk worked on understanding the coastal dynamics of California, from studying the erosion patterns of beaches to analyzing how global warming might impact the state’s famous coastal cliffs.

His legacy continues to shape how California manages its vast coastline. The methodologies and insights he developed in wave prediction are now used in environmental and civil engineering projects that protect harbors, beaches, and coastal infrastructure from wave damage. As climate change accelerates the rate of sea level rise, Munk’s work on tides, ocean currents, and wave dynamics is more relevant than ever for California’s future.

Walter Munk’s contributions to oceanography stretched well beyond his wartime work and Project Mohole. He was instrumental in shaping how we understand everything from deep-sea currents to climate patterns, earning him numerous awards and accolades. His work at Scripps set the stage for the institution’s current status as a world leader in oceanographic research.

One of the most notable examples of this work was an experiment led by Munk to determine whether acoustics could be used to measure ocean temperatures on a global scale, offering insights into the effects of global warming. In 1991, Munk’s team transmitted low-frequency underwater acoustic signals from a remote site near Heard Island in the southern Indian Ocean. This location was strategically chosen because sound waves could travel along direct paths to listening stations in both the Pacific and Atlantic Oceans. The experiment proved successful, with signals detected as far away as Bermuda, New Zealand, and the U.S. West Coast. The time it took for the sound to travel was influenced by the temperature of the water, confirming the premise of the study.

Walter Munk in 2010 after winning the Crafoord Prize. (Crafoord Prize)

Munk passed away in 2019 at the age of 101, but his influence lives on. His approach to science—marked by curiosity, boldness, and a willingness to take on complex, high-risk projects—remains an inspiration for generations of scientists. He was a giant not only in oceanography but also in shaping California’s role in global scientific innovation. As the state faces the challenges of a changing climate, Munk’s legacy as the “Einstein of the Oceans” continues to be felt along its shores and beyond.

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John Isaacs, the Maverick Oceanographer Who Wanted to Tow Icebergs to California

An AI rendering of Isaacs’ bold idea (Midjourney)

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California’s water crises have always inspired bold solutions, but few ideas rival the sheer audacity of John Isaacs’ proposal to tow a giant Antarctic iceberg to San Diego. A brilliant and unconventional researcher at the Scripps Institution of Oceanography, Isaacs made waves in 1949 with his imaginative, though controversial, plans to quench California’s chronic droughts by harnessing the frozen reservoirs of the polar regions.

Isaacs’ career was defined by his boundary-pushing ideas. A polymath with a keen interest in marine biology, engineering, and climate science, he often operated at the intersections of disciplines, challenging conventional thinking. The iceberg-towing proposal exemplified his knack for blending vision and pragmatism—if one were willing to stretch the definition of “pragmatic.”

Isaacs theorized that large Antarctic icebergs could be wrapped in insulation to slow their melting and then towed by tugboats up the Pacific coast. The journey, spanning thousands of miles, would end with the iceberg positioned off the coast of Southern California, where its meltwater could be harvested to replenish reservoirs. Isaacs estimated that a single large iceberg, some the size of Manhattan, could supply tens of billions of gallons of freshwater—enough to offset drought conditions for millions of people.

John D. Isaacs (Scripps Institution of Oceanography)

The concept wasn’t a fleeting thought. Isaacs expanded on his idea in 1956, suggesting the capture of an eight-billion-ton iceberg—20 miles long, 3,000 feet wide, and 1,000 feet deep—and towing it to San Clemente Island off San Diego in approximately 200 days. He even calculated that a fleet of six ocean-going tugs could accomplish the feat, taking about six months to tow the iceberg from the 65th parallel south to the Californian coast.

In October 1973, the RAND Corporation took Isaacs’ vision further with an extensive report titled “Antarctic Icebergs as a Global Fresh Water Source” for the National Science Foundation. This 96-page document, authored by J.L. Hult and N.C. Ostrander, provided the most detailed scheme to date, transforming the theoretical idea into a more structured and mathematical model. It envisioned the creation of an “iceberg train” and delved into the technicalities and logistics of towing icebergs across the ocean. Hult explained, “Bringing icebergs to where the water is needed was suggested by John Isaacs of Scripps Institute of Oceanography in the 1950s. It is our job to show how practical it is.” However, the plan was not without eccentricities—such as the suggestion of using a floating nuclear power plant to supply the energy needed for the operation. The RAND report exemplified the ambition of its era, though many of its assumptions leaned heavily on theoretical modeling rather than practical viability.

AI rendering of an iceberg being dismantled (Midjourney)

Isaacs wasn’t alone in dreaming big. His proposal came at a time when other researchers and engineers were exploring similarly outlandish ideas, like seeding clouds with silver iodide to induce rain or building massive aqueducts from Alaska. But Isaacs’ iceberg scheme captured imaginations for its sheer romance and its symbolic uniting of Earth’s polar extremes with parched California landscapes.

Isaacs knew his plan faced enormous technical, logistical, and financial hurdles. For one, towing an iceberg would require immense energy and coordination, as well as a fleet of powerful ships. The iceberg’s tendency to melt during transit—especially when entering warmer waters—posed another significant obstacle. To mitigate this, Isaacs suggested covering the iceberg in reflective materials or insulating blankets to slow heat absorption.

Then there was the issue of economics. Calculations revealed that the cost of transporting a single iceberg could run into the billions, far outweighing the price of more conventional water solutions like desalination plants or water recycling programs. Critics also worried about ecological disruption, from changing ocean currents to the impact on marine ecosystems along the iceberg’s route.

While Isaacs’ iceberg idea was never realized, it sparked a wave of creative thinking about unconventional water solutions. Today, some of the principles behind his ideas have resurfaced in modern innovations. Advanced engineering methods, including climate-resilient infrastructure and adaptive water management, owe a debt to the exploratory spirit of Isaacs’ era.

AI rendering of an aqueduct built to carry water from Alaska to California (Midjourney)

The iceberg-towing concept is occasionally revisited, especially as climate change intensifies water scarcity. For example, in recent years, researchers in the United Arab Emirates have considered similar plans to bring freshwater from polar ice to arid regions. Advances in materials science and energy efficiency have made some aspects of Isaacs’ vision more feasible, though the logistics remain daunting.

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John Isaacs’ career extended far beyond icebergs. He contributed to deep-sea exploration, studied the effects of nuclear fallout on marine life, and was an early advocate for understanding the ocean’s role in climate systems. His interdisciplinary approach and willingness to embrace unorthodox solutions left a lasting impact on oceanography and environmental science.

Isaacs’ iceberg proposal remains a testament to his fearless creativity and his deep commitment to solving humanity’s greatest challenges. While the world never saw an iceberg floating past Los Angeles, Isaacs’ bold thinking continues to inspire researchers grappling with the complex interplay of science, technology, and the environment.

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The Great Los Angeles Flood of 1934 was a Disaster That Shaped California’s Approach to Flood Control

A house in the La Crescenta-Montrose area was swept off its foundation and carried several hundred feet by the
New Year’s Eve floodwaters. (LA Times)

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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.

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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.

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Get Your Nukes on Route 66: The Wild Plan to Use Nuclear Weapons to Blast a Highway Through the California Desert

…and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more. Micah 4:3

Fake rendering of an atomic bomb exploding near road in Mojave Desert.

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In the early 1960s, the U.S. government seriously considered using nuclear bombs to solve a civil engineering challenge: building a highway bypass through the rugged terrain of California’s Mojave Desert. Dubbed Project Carryall, the plan would have involved detonating a series of nuclear devices to blast a path for a stretch of highway and railroad intended to reroute Route 66 and ease congestion. The idea sounds absurd today, but at the time, the U.S. was actively exploring ways to use nuclear energy for peaceful purposes.

Project Carryall was part of a broader initiative known as Operation Plowshare, launched by the Atomic Energy Commission (AEC) to explore the potential of using nuclear explosions in constructive ways. Proposed ambitious projects included using nuclear explosions for excavation, mining, and infrastructure development. Ideas included creating artificial harbors, digging new canals like the “Pan-Atomic Canal,” stimulating natural gas production through underground detonations, and creating tunnels or underground reservoirs.

The idea was conceived in 1951 as a way of “beating atomic arms into plowshares.” The underlying logic was that controlled nuclear blasts could do the work of traditional excavation on a much larger and faster scale. Proponents of the project, including argued that using nuclear bombs could reduce the time and cost involved in these types of infrastructure projects, providing a technological leap forward.

Edward Teller, a key figure in the development of the hydrogen bomb, was actively involved in promoting Project Carryall as part of his broader support for Operation Plowshare. His earlier contributions to the successful creation of the H-bomb in 1952 helped cement his reputation as a leading nuclear physicist, and he saw projects like Carryall as a way to repurpose atomic energy for large-scale civil engineering projects.

Teller was a highly controversial figure due to his staunch advocacy for the use of nuclear technology, both in weapons development and peaceful applications like Project Carryall. His role in the hydrogen bomb’s creation, along with his support for large-scale nuclear projects, earned him both admiration and criticism, particularly after he testified against Robert Oppenheimer, which many viewed as a betrayal of his fellow scientists. Teller, who died in 2003, went to his grave convinced that nuclear geo-engineering was a missed opportunity.

Schematic and map of Project Carryall in the California Desert

The proposal for Project Carryall specifically targeted the construction of a new transportation corridor in Southern California. By the early 1960s, Route 66 had become notorious for traffic bottlenecks, particularly as postwar car ownership and travel boomed. To bypass the tight curves and mountainous terrain of the Cajon Pass area, engineers envisioned a straighter, more efficient route through the Bristol Mountains. The task of carving out such a path would have been an immense undertaking with traditional methods. Enter the nuclear option. Maybe we could dig with the bomb.

A feasibility study conducted by the Atchison, Topeka, and Santa Fe Railway (ATSF) sought assistance from the U.S. Atomic Energy Commission citing the Bristol Mountains as the ideal location for the project. Collaborating with the Commission’s San Francisco office and the Lawrence Radiation Laboratory (now the Lawrence Berkeley National Laboratory and a Department of Energy-funded U.C. Berkeley offshoot), the study concluded that a nuclear-excavated bypass was not only “technically feasible” but also significantly cheaper than traditional excavation methods.

Project Carryall aimed to carve a path through the Bristol Mountains, about 11 miles north of Amboy, California, a popular stop along Route 66, using 22 nuclear devices with yields ranging from 20 to 200 kilotons. Engineers planned to drill holes along a 10,940-foot section of the mountainside, each 36 inches in diameter and between 343 to 783 feet deep, reinforced with corrugated metal to house the nuclear explosives. These detonations, which would have been fired in two groups of 11 simultaneously, were expected to remove around 68 million cubic yards of earth, creating a cut up to 360 feet deep and between 600 and 1,300 feet wide. The total yield of the explosions, 1,730 kilotons, was equivalent to about 115 times the explosive power of Little Boy, the atomic bomb dropped on Hiroshima. The blasts would have essentially carved the path through the mountains in seconds.

Project *Storax Sedan* shallow underground nuclear test by the United States, used for a cratering experiment. 6 July 1962, Nevada Test Site Yield: 104 kt. The main purpose of the detonation was to asses the non military dimension of a nuclear explosion.

Citing data from 1962’s Project Sedan, the Atomic Energy Commission estimated that work in the area could safely resume just four days after the nuclear detonation. This projection was highlighted in a 2011 report by the Desert Research Institute, affiliated with the University of Nevada, Reno, which examined the feasibility and safety of such operations during the era of nuclear excavation projects. The Sedan nuclear test displaced around 12 million tons of earth with a single 104-kiloton blast. This test created a massive crater and sent radioactive debris into the atmosphere.

The 1962 “Sedan” plowshares shot displaced 12 million tons of earth and created a crater 320 feet deep and 1,280 feet wide.
(National Nuclear Security Administration)

The projected combined costs for the railroad tunnel and highway in Project Carryall were estimated at $21.8 million, equivalent to roughly $216.96 million today. The nuclear excavation method was expected to cost $13.8 million (about $137.34 million in 2023 dollars), excluding the price of the nuclear devices themselves. Traditional excavation was estimated at $50 million, or approximately $497.61 million today. Although the cost of the nuclear devices was classified, it was assumed to be less than the gap between conventional and nuclear methods, making the nuclear approach seem more cost-effective at the time.

Mid-20th century scientists envisioned a new Panama Canal blasted down to sea level with thermonuclear explosives. (Lawrence Livermore National Laboratory)

As wild as this plan seems today, it wasn’t entirely out of place in the context of its time. The Cold War era was marked by an optimistic belief in the power of technology, particularly nuclear technology, to solve big problems. With Operation Plowshare, the U.S. government was looking for ways to demonstrate the peaceful uses of nuclear energy. Proponents of Project Carryall framed the use of nuclear devices for highway construction as a sign of progress, imagining a future where atomic energy could help reshape the American landscape in new and innovative ways.

However, there were significant hurdles to the project’s realization, many of them environmental and logistical. Although the AEC touted the precision of the nuclear blasts, the potential consequences of radiation were harder to dismiss. The detonation of nearly two dozen nuclear devices in the middle of California’s desert would likely have released dangerous levels of radioactive fallout, contaminating the land, air, and possibly even water supplies for nearby communities. Engineers also anticipated “occasional rock missiles” projected as far as 4,000 feet (1,200 m) from the blasts. While the nearby town of Amboy was not expected to experience significant effects, there was greater concern about the impact on a natural gas pipeline in the vicinity, which would require pre-blast testing to assess potential risks. Further, concerns about the safety of workers, residents, and wildlife made it increasingly difficult to justify the project.

Project Carryall was abandoned due to a combination of environmental, political, and logistical concerns. As public awareness of the dangers of nuclear fallout grew, the potential for radioactive contamination became a significant issue, especially with the predicted large dust cloud and the risk to nearby natural gas pipelines. The signing of the Limited Test Ban Treaty in 1963, which prohibited nuclear tests that produced radioactive debris across borders, further complicated the project’s prospects. Moreover, the environmental movement was gaining traction during the 1960s, leading to increased opposition to nuclear excavation. Traditional construction methods, though more costly and time-consuming, were ultimately deemed safer and more politically feasible. By the mid-1960s, the California Highway Division (Now Caltrans) withdrew from the project, and nuclear excavation was abandoned in favor of conventional approaches. The highway bypass was eventually constructed using traditional methods, without the need for nuclear blasts.

Project Carryall Marker sign in Ludlow, California

While it never came to fruition, Project Carryall remains a striking example of the U.S. government’s audacious postwar optimism and the belief that nuclear technology could solve even the most mundane problems. It serves as a reminder of the tension between technological ambition and environmental responsibility—a lesson that resonates even more today. The story of Project Carryall is one of the stranger chapters in the history of America’s nuclear age, but it highlights how far we’ve come in understanding the limits and dangers of nuclear energy beyond warfare.

Today, the Carryall project is memorialized by a roadside marker in Ludlow, the nearest town to the west of the site.

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Unearthing the Secrets of the Sierra Nevada Batholith

An example of Sierra Nevada batholith. There are several domes in Yosemite besides Half Dome. (Erik Olsen)

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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).

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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.

The Lost Island of Santarosae off California’s Coast

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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.

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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.

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.

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New Research Sheds Light on the Saber-Toothed Cats of California, Fierce Predators of the Pleistocene

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Around 15,000 to 20,000 years ago, the landscape near present-day Los Angeles was a diverse mix of environments shaped by the end of the Ice Age. Cooler and wetter than today, it was dominated by savannah-like grasslands, wetlands, and patches of dense forests filled with towering oaks and pines. Prehistoric rivers and lakes dotted the landscape, nourishing a rich ecosystem teeming with life. Massive herbivores like mammoths, giant ground sloths, bison, and ancient camels roamed these plains, foraging on abundant grasses and shrubs.

Among these creatures of the Pleistocene Epoch, predators like saber-toothed cats (Smilodon fatalis) ruled, using the cover of forests and brush to ambush their prey. These large cats thrived alongside other carnivores like dire wolves and American lions, each species carving out its niche. However, the landscape was in flux—warming temperatures gradually dried out the environment, increasing the frequency of wildfires and altering the balance of flora and fauna. As human populations expanded and hunted large herbivores, the delicate ecosystem began to unravel, setting the stage for the extinction of many of the region’s iconic megafauna (more on this later).

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Saber-toothed cats are some of the most iconic prehistoric predators to have roamed California. Known for their distinctive long, blade-like canine teeth, these powerful carnivores thrived during a time when much of North America was covered in ice and the landscape teemed with large herbivores. Fossils of these magnificent creatures have been found across the state, with an impressive concentration in the famous La Brea Tar Pits in Los Angeles, revealing a vast amount of details about their biology, natural history, and the world they lived in. In fact, thousands of skeletons are preserved in the Rancho La Brea Tar Pits, making it the largest and most significant site for studying saber-tooth cats and other Pleistocene-era animals.

But first, let’s clear up a few things. The terms “saber-toothed tiger” and “saber-toothed cat” are often used interchangeably, but they refer to different concepts, and the distinction is important for scientific accuracy. “Saber-toothed tiger” is a misnomer because these prehistoric animals were not true tigers, nor were they closely related to them. Instead, they belonged to a now-extinct subfamily of felines called Machairodontinae, with the most famous genus being Smilodon. Modern tigers, on the other hand, belong to the Panthera genus and are part of a completely different evolutionary line. The term “saber-toothed cat” is more accurate because it reflects the broader diversity of species in this group, not just a single “tiger-like” animal. This distinction is crucial because it prevents confusion in understanding the evolutionary history of felines and avoids spreading inaccuracies in the scientific and popular understanding of extinct species.

A great deal of modern research has been conducted on the saber-tooth cat, ranging from genetic studies to isotopic analysis, fossil reconstruction, and insights into their ecological role during the Pleistocene Epoch. In fact, in 2020 researchers from the University of Copenhagen mapped the entire nuclear genome of a sabre-toothed cat known as Homotherium. The genetic study revealed new insights about a socially intelligent pack animal, that specialized in endurance-based hunting over long distances.

The cover of the 1908 October issue of *Sunset* magazine.

When you look at the fossilized skeletons of saber-toothed cats on display at the La Brea Tar Pits, it’s easy to imagine these powerful predators silently stalking their prey through the ancient landscapes, ready to spring with sharp, curved teeth bared and bloody from an earlier meal. Their upper canine teeth were long, sharp, and curved like sabers, often reaching lengths of up to 7 inches (18 cm). Unlike the teeth of modern big cats, which are built for biting and holding prey, the saber teeth were relatively fragile and not ideal for crushing bones. This suggests that these animals had to be precise in how they used their teeth to kill.

Saber toothed cat skull at La Brea Tar Pits (Erik Olsen)

Rather than relying on brute force to clamp down on their prey, saber-toothed cats likely used their teeth to deliver deep, slashing wounds to vulnerable areas, such as the neck, throat, or belly of large herbivores. Some scientists believe that after overpowering their prey with their strong forelimbs, they would deliver a quick, lethal bite, severing major blood vessels or the windpipe. The killing technique of saber-toothed cats was likely specialized for large, slow-moving prey like bison, mammoths, or camels.

Saber-toothed cat (*Smilodon fatalis*). (Indiana State Museum)

This precision style of hunting contrasts with how modern big cats, like lions, use their teeth to bite and hold, crushing the windpipe or suffocating their prey. The saber-toothed cat’s teeth were well-adapted to slicing, but not to the prolonged grip needed for suffocation.

A recent study on saber-toothed cats from paleontologist Jack Tseng of the University of California, Berkeley, reveals that juvenile cats retained their baby teeth alongside their developing adult fangs, likely as a stabilizing mechanism. This double-fanged stage, lasting up to 30 months, helped protect the growing sabers from breaking as young cats learned to hunt. Through computer simulations and mechanical tests, researchers demonstrated that the baby tooth acted as a buttress, reducing the risk of saber damage during this critical learning phase. This finding offers new insights into the hunting development of these prehistoric predators.

The cranium of a *Smilodon* with fully-erupted sabers (Jack Tseng)

Modern research is uncovering potential new insights into the saber-tooth cat’s behavior, including possible hunting techniques, social structures, and interactions with other species. Paleontologists have found fossilized throat bones in Smilodon at the La Brea Tar Pits similar to those in modern big cats like lions and tigers, suggesting that these prehistoric predators may have also roared with powerful vocalizations.

One of the most fascinating debates surrounding Smilodon is whether they hunted alone or in groups. Further fossil evidence from the La Brea Tar Pits suggests that these cats may have lived and hunted in social groups, similar to modern lions. Many Smilodon skeletons show evidence of healed injuries, which has led paleontologists to believe that they may have cared for each other in social settings, allowing injured individuals to recover rather than being abandoned. This level of social cooperation would have been an important adaptation in a world full of dangerous megafauna, enabling them to take down larger prey.

Prehistoric scene with saber-toothed cat.

The extinction of saber-toothed cats, specifically Smilodon, in California has been a subject of extensive research. A study from 2023 published in the prestigious journal Science shows just how quickly the largest animals disappeared from the La Brea fossil record. Scientists from the La Brea Tar Pits, including a University of Oregon professor and postdoctoral researcher, employed a computer model to explore how factors like wildfires, climate change, species loss, and human presence interacted. This revealed a far more intricate explanation for the extinctions than earlier theories, which often pinned the blame on a single factor such as human overhunting or climate shifts. According to the study, humans likely played a pivotal role by driving herbivores to extinction, which in turn led to an overgrowth of vegetation, creating fuel for wildfires. At the same time, the climate was becoming drier, compounding the problem, and leaving carnivores without sufficient prey to survive.

**Sequence of ecological events as recorded at Rancho La Brea, California.** (Natural History Museum of Los Angeles County)

Although most of the existing fossils came from the La Brea Tar Pits in Los Angeles, Smilodon was widely distributed across North America, from coast to coast, reaching as far north as Idaho and Nebraska and extending south into South America. It is most famously associated with California and Florida. The oldest known fossil of Smilodon dates back approximately 500,000 years, while the youngest, discovered during bank construction in Nashville, Tennessee, is just 9,400 years old.

Saber-toothed cat fossil skeleton at La Brea Tar Pits (Erik Olsen)

The La Brea tar pits are a unique and incredibly fruitful outdoor laboratory for understanding animals from 50,000 years of the Pleistocene and the environment in which they lived. Paleontologists have unearthed thousands of Smilodon bones, providing a wealth of information about their anatomy and behavior. The bones show a high rate of injuries, including broken bones and bite marks, which supports the idea that these cats faced significant risks when hunting. In addition to Los Angeles, saber-toothed cat fossils have been found in various parts of California, including San Diego and along the Central Valley, though the La Brea Tar Pits remains the most prolific source.

Imagine that. One of the greatest fossil sites in the world lies amidst the skyscrapers and traffic-clogged streets of Los Angeles. It’s kind of mind-boggling.

Despite their extinction, the legacy of saber-toothed cats endures in the fossil record and in our imagination. Because of it’s ability to capture public interest, ane because the fossil record is so abundant and varied, Smilodon fatalis is now the state fossil of California, symbolizing the state’s rich prehistoric past.

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