Tag: nature

The Scourge of Ghost Lobster Traps and the Battle to Save Marine Life in California

Ghost lobster trap off Santa Cruz Island in California’s Channel Islands (Photo: Erik Olsen)

Lobster is delicious. Let’s just get that out of the way. Yes, I’m sure there are some who either don’t enjoy the taste of this prolific crustacean, or who are allergic, but for my part, lobster (with a small vial of melted butter) is ambrosia from the sea.

But beyond its place on the plate, the California spiny lobster plays a vital ecological role: hunting sea urchins, hiding in rocky reefs, and helping to keep kelp forests in balance. Its value extends far beyond what it fetches at market. But beneath the surface, particularly around the Channel Islands lurks a growing problem that doesn’t just threaten lobsters. It threatens the entire marine ecosystem: ghost traps.

Dive ship Spectre off of Anacapa Island in California’s Channel Islands (Photo: Erik Olsen)

In Southern California, lobster fishing is both a cultural tradition and a thriving industry, worth an estimated $44 million annually to California’s economy from commercial landings as well as recreational fishing, tourism, and seafood markets.

In late April, I traveled to the Channel Islands with my colleague Tod Mesirow to see the problem of ghost lobster traps firsthand. We were aboard the Spectre dive ship and pulled out of Ventura Harbor on an overcast morning, the sky a uniform gray that blurred the line between sea and cloud. The swell was gentle, but the air carried a sense of anticipati on. We were invited by the Benioff Ocean Science Laboratory, which is conducting research and outreach in the area. Our visit took us to Anacapa and Santa Cruz Islands, where I would be diving to observe the traps littering the sea floor. Tod, meanwhile, remained topside, capturing footage and speaking with marine scientists. Even before entering the water, we could see the toll: frayed lines tangled in kelp, buoys adrift, and entire areas where dive teams had marked clusters of lost gear.

California spiny lobsters alive when the ghost trap was recovered (Photo: Erik Olsen)

Ghost traps are lobster pots that have been lost or abandoned at sea. Made of durable metal mesh and often outfitted with bait containers and strong ropes, these traps are built to last. And they do. For years. Sometimes decades. The problem is, even when their human operators are long gone, these traps keep fishing.

“It’s not uncommon to find multiple animals dead inside a single trap,” said Douglas McCauley, a marine science professor at UC Santa Barbara and director of the Benioff Ocean Science Laboratory who was onboard with us and leading the project. “It’s heartbreaking. These traps are still doing exactly what they were built to do, just without anyone coming back to check them.”

Douglas McCauley, director of the Benioff Ocean Science Laboratory at the University of California Santa Barbara holding a lobster caught in a ghost trap off the coast of the Channel Islands (Photo: Erik Olsen)

Around the Channel Islands National Marine Sanctuary, where fishing pressure is high and waters can be rough, thousands of traps are lost every season. Currents, storms, or boat propellers can sever buoys from their lines, leaving the traps invisible and unrecoverable. Yet they keep doing what they were designed to do: lure lobsters and other sea creatures inside, where they die and become bait for the next unfortunate animal. It’s a vicious cycle known as “ghost fishing.”

“They call them ghost traps because, like a ghost sailing ship, they keep doing their thing. They keep fishing.” said McCauley.

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Statewide, the numbers are staggering. Approximately 6,500 traps are reported lost off the California coast each fishing season, according to The California Department of Fish and Wildlife. The folks at the Benioff Ocean Science Laboratory said as many as 6,000 may lie off the coast of the Channel Islands alone. Ocean Divers removing marine debris have found traps stacked three and four high in underwater ravines—rusting, tangled, but still deadly. These ghost traps don’t just catch lobsters; they also trap protected species like sheephead, cabezon, octopuses, and even the occasional sea turtle or diving seabird.

Diver and Project Scientist Chase Brewster of the Benioff Ocean Science Laboratory collecting data on ghost lobster traps near California’s Channel Islands (Photo: Erik Olsen)

Nowhere is this more evident than around the Channel Islands. These rugged islands are home to some of California’s richest kelp forests and underwater canyons. The islands and their surrounding waters are home to over 2,000 plant and animal species, with 145 of them being unique to the islands and found nowhere else on Earth. In fact, the Channel Islands are often referred to as North America’s Galapagos for the immense diversity of species here.

The islands are also the site of the state’s most productive spiny lobster fisheries. Every fall, hundreds of commercial and recreational fishers flood the area, setting thousands of traps in a race to catch California spiny lobsters (Panulirus interruptus). But rough swells and heavy gear mean traps go missing. Boats sometimes cut the lines of traps, making them near impossible to retrieve from the surface. And because this region is a patchwork of state waters, federal waters, and marine protected areas (MPAs), cleanup and regulation are anything but straightforward.

California Spiny Lobster off Anacapa Island (Photo: Erik Olsen)

The traps are often difficult to locate, partly because of their remote placement and the notoriously rough waters around the Channel Islands. But the Benioff Ocean Science Laboratory has a powerful asset: side scan sonar. From the ship, they can scan and map the seafloor, where the ghost traps often appear as dark, rectangular shapes against the sand. Once spotted, the team uses GPS to log their exact location.

“It’s creates a picture made of sound on the seafloor and you see these large lego blocks staring at you in bright yellow on the screen and those are your lobster traps,” sayd McCauley. “There’s nothing else except a ghost trap that looks like that.”

Plunging into the frigid waters off Santa Cruz Island was a jolt to the system. Visibility was limited, just 10 to 15 feet, but I followed two scientists from the Benioff Ocean Science Laboratory down to a depth of 45 feet. Their task: to attach a rope to the trap so it could be hauled up by the boat’s winch.

Dive ship Spectre off the coast of Santa Cruz Island in California’s Channel Islands (Photo: Erik Olsen)

The water was thick with suspended particles, the light dimming quickly as we dropped lower. My 7mm wetsuit was just barely enough to stave off the cold. On the seafloor, the ghost trap emerged, a large rectangular cage resting dark and ominous in the sand. And it was teeming with life. Fish darted around its edges, lobsters clambered along the frame, and inside, several animals moved about, trapped and slowly dying. It was easy to see how a single trap could wreak quiet havoc for years.

California law technically requires all lobster traps to include biodegradable “escape panels” with zinc hinges that degrade over time, eventually allowing trapped animals to escape. But enforcement is tricky, and the panels don’t always work as intended. In practice, many traps, especially older or illegally modified ones, keep fishing long after they should have stopped. That’s what we were out here to find.

A baby octopus caught in a ghost trap in the waters off California’s Channel Islands (Photo: Erik Olsen)

Complicating matters is the fact that once a trap goes missing, there’s no easy way to retrieve it. Fishers are not legally allowed to touch traps that aren’t theirs, even if they’re obviously abandoned. And while a few small nonprofits and volunteer dive teams conduct periodic ghost gear removal missions, they can’t keep pace with the scale of the problem.

“At this fishery, we can’t get them all,” says McCauley. “But by going through and getting some species out and getting them back in the water, we’re making a difference. But in the process, we’re coming up with new ideas, new technologies, new research methods, which we think could play a role in and actually stopping this problem in the first instance.”

Once abundant along California’s coast, this large abalone spotted off Santa Cruz Island is a rare sight today—a quiet reminder of how overfishing, disease, and environmental change have decimated their populations. (Photo: Erik Olsen)

Back topside, the recovery team aboard the Spectre used a powerful hydraulic winch to haul the trap onto the deck. After climbing out of the cold water, still shivering, I joined the others to get a closer look. The trap was heavy and foul-smelling, but what stood out most was what was inside: lobsters, maybe ten or more. Some had perished, but many were alive and thrashed their tails when lifted by the scientists. Females could be identified by their broader, flatter tail fins—adapted to hold eggs. The team carefully measured each one before tossing them back into the sea, the lobsters flipping backward through the air and disappearing into the depths.

There were other animals, too. Large, rounded crabs known as Sheep crabs, common to these waters, scuttled at the bottom of the trap. Sea snails were clustered along the mesh, and in one cage, there were dozens of them, clinging and crawling with slow purpose. Even baby octopuses made appearances, slithering out onto the deck like confused aliens. I picked one up gently, marveling at its strange, intelligent eyes and soft, shifting forms, before tossing it back into the sea in hopes it would have another chance at life.

Ghost lobster trap lies on the seafloor off of Santa Cruz Island in California’s Channel Islands (Photo: Erik Olsen)

By then, the day had brightened and the sun had come out, easing the chill that lingered after the dive. The traps would be taken back to Ventura, where they’d likely be documented and disposed of. But this day wasn’t just about saving individual animals or pulling traps off the seafloor—it was about data. The Benioff team wants to understand just how big of a problem ghost traps really are. It’s not just about the number of traps lost each season, but the broader ecological toll: how many animals get caught, how many die, and how these traps alter the underwater food web. Every recovered trap adds a piece to the puzzle. This trip was about science as much as rescue.

State agencies, including the California Department of Fish and Wildlife (CDFW), have started pilot programs aimed at tackling ghost gear. In 2023, CDFW launched a limited recovery permit program that allows fishers to collect derelict traps at the end of the season, provided they notify the state. But participation is voluntary and poorly funded.

Elsewhere, states like Maine and Florida have created large-scale, state-funded programs to identify and remove ghost traps, often employing fishers in the off-season. California, despite having the nation’s fourth-largest lobster fishery, has yet to make a similar investment.

Ghost lobster traps recovered from the seafloor off the coast of California’s Channel Islands (Photo: Erik Olsen)

Some solutions are already within reach. Mandating GPS-equipped buoys for commercial traps could help track and retrieve gear before it’s lost. More robust escape hatch designs, made from materials that dissolve in weeks rather than months, would shorten the lifespan of a lost trap. And expanding retrieval programs with funding from fishing license fees or federal grants could make a big dent in ghost gear accumulation.

But even more powerful than regulation may be public awareness. Ghost traps are out of sight, but their damage is far from invisible. Every trap left behind in the Channel Islands’ waters becomes another threat to biodiversity, another source of plastic and metal waste, and another reminder that marine stewardship doesn’t stop when the fishing season ends.

Key to the whole effort is data:

“Every one of the animals that we put back in the water today, we’ll be taking a measure,” says McCauley. “After a little bit of crunching in the lab, we’ll be able to say, oh, actually, you know, every single trap undercuts the fishery by x percent for every single year that we don’t solve the problem.”

Doug McCauley with a lobster trap retrieved from the seafloor off the coast of California’s Channel Islands (Photo: Erik Olsen)

As we headed back toward Ventura, Tod and I talked with Douglas McCauley and Project Scientist Neil Nathan from the Benioff Ocean Science Laboratory. The team had collected a total of 13 traps that day alone, and 34 over the several days they’d been out. There was a sense of satisfaction on board, quiet but real. Each trap removed was a small win for the ecosystem, a little less pressure on an already strained marine environment.

“I would call today an incredible success, ” said Neil Nathan. “Feeling great about the number of traps we collected.”

California has long been a leader in ocean conservation. If it wants to stay that way, it needs to take ghost fishing seriously, not just around the Channel Islands, but up and down the coast. After all, we owe it to the lobsters, yes, but also to the underwater forests, reef communities, and countless species whose lives are tangled in the nets we leave behind.

The Plate Tectonic Revolution and How California Became the Epicenter of a Scientific Breakthrough

How the 1969 Penrose Conference on plate tectonics at Asilomar in California transformed our understanding of Earth’s dynamic processes.

Aerial photo of San Andreas Fault looking northwest onto the Carrizo Plain with Soda Lake visible at the upper left. (Wikipedia)
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Before the late 1960s, understanding Earth’s shifting surface, particularly in a geologically active region like California, was a major scientific challenge. For most of human history, the causes of earthquakes remained an enigma—mysterious and terrifying, often attributed to supernatural forces. In Japan, for example, earthquakes were traditionally believed to be caused by Namazu, a giant catfish said to live beneath the earth and whose thrashing would shake the land. Many societies believed earthquakes were divine punishments or omens, while others considered them an essential part of creation, events necessary to form a world habitable by us humans.

The complexity of California’s landscape, its mountains, valleys, deserts, and intricate network of faults, posed difficulties for early geologists. The land appeared chaotically interwoven, with many different types of rock making up the gaping deserts and soaring peaks. As the great University of California at Davis geologist Eldridge Moores once put it, “Nature is messy. Don’t expect it to be uniform and consistent.”

An image of humans battling a Namazu (Credit: Tokyo University Library. Public Domain)

But there was no overarching explanation for how these earthly features got there. Scientists could observe and record earthquakes, but without a unifying theory, they struggled to piece together the deeper mechanisms driving these powerful events.

This frustration lingered until the late 1960s when an intellectual revolution in geology took shape. Despite the dawn of the space age and the rise of computing power, many earth scientists still clung to the belief that the continents were fixed, immovable features on the Earth’s surface. The breakthrough came with the acceptance of plate tectonics—a theory that elegantly explained not just earthquakes, but the entire dynamic nature of Earth’s surface. And for many geologists, the moment this new understanding solidified was in December 1969, at a groundbreaking conference at the Asilomar Conference Center in California that reshaped the future of the field. (Notably, Asilomar was also the site of the historic 1975 conference on recombinant DNA, where scientists gathered to establish ethical guidelines for genetic research, an event we have explored previously.) This was the moment when plate tectonics, a concept that would fundamentally reshape our view of the planet, truly took hold in the Western American geological community.

At California’s Asilomar Conference Grounds, nestled amid Monterey pines and dramatic granite formations, scientists gathered to rewrite our understanding of tectonics—and reshape how we think about Earth’s restless surface. (Erik Olsen)

For centuries, explanations for Earth’s features ranged from catastrophic events to gradual uplift and erosion, a debate that became known as uniformitarianism versus catastrophism. In California, the sheer complexity of the geology, with its links go far beyond the borders of the state, hinted at powerful forces at play. Scientists grappled with the origins of the Sierra Nevada, the formation of the Central Valley, and the persistent threat of earthquakes along the now-famous San Andreas Fault. The prevailing models, however, lacked the comprehensive framework to connect these disparate observations into a coherent narrative.

The seeds of the plate tectonic revolution had been sown earlier in the 20th century with Alfred Wegener’s theory of continental drift. Anyone looking at a world map or globe could see how the coastlines of certain continents, particularly South America and Africa, seemed to fit together like pieces of a puzzle, suggesting they were once joined. Wegener proposed that the continents were once joined together in a supercontinent called Pangaea and had gradually drifted apart over millions of years. While his ideas were initially met with skepticism, particularly regarding the mechanism that could drive such massive movements, compelling evidence from paleontology, glacial geology, and the jigsaw-like fit of continental coastlines slowly began to sway opinions. The discovery of seafloor spreading in the 1960s (itself a great story, featuring the brilliant geologist and cartographer Marie Tharp) which revealed that new oceanic crust was constantly being generated at mid-ocean ridges and that the ocean floor itself was moving like a conveyor belt, provided the crucial mechanism Wegener lacked.

Heinrich Berann’s 1977 painting of the Heezen-Tharp “World Ocean Floor” map, a landmark in cartography that showed how the earths plates in some areas are pulling apart while others collide. (Library of Congress)

It was against this backdrop of burgeoning evidence that the Geological Society of America convened one of its annual Penrose Conferences in December 1969 at the Asilomar Conference Center in Pacific Grove, California. Titled “The Meaning of the New Global Tectonics,” the event drew structural geologists from all over the world.  The geological world changed overnight. A key figure in the conference was William R. Dickinson, a leading structural geologist whose work helped bridge the gap between traditional geological interpretations and the emerging plate tectonic framework. Dickinson’s research on sedimentary basins and tectonic evolution provided critical insights into how plate movements shaped the western United States, further solidifying the new theory’s acceptance.

These conferences were designed to be intimate gatherings where geologists could engage in focused discussions on cutting-edge research. The 1969 meeting proved to be a pivotal one. As UC Davis’ Moores, then a youthful figure who would become a leading voice of the “New Geology” in the West, later wrote, “the full import of the plate tectonic revolution burst on the participants like a dam failure”.

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

Paper after paper presented at the conference demonstrated how the seemingly simple notion of large plates floating atop the Earth’s plastic mantle (the asthenosphere) could explain a vast array of geological phenomena. The location of volcanoes, the folding of mountains (orogeny), the distribution of earthquakes, the shape of the continents, and the history of the oceans all suddenly found a compelling and unified explanation within the framework of plate tectonics. Geologist John Tuzo Wilson famously referred to plate tectonics as ‘the dance of the continents,’ a phrase that captured the excitement and transformative nature of this intellectual breakthrough.

For Moores, the conference was a moment of profound realization. “It was a very exciting time. I still get goosebumps even talking about it,” he told the writer John McPhee. “A turning point, I think it was, in the plate tectonic revolution, that was the watershed of geology.” Moores had been contemplating the perplexing presence of ophiolite sequences – distinctive rock assemblages consisting of serpentines, gabbro/lava, and sediments – found high in the mountains of the West, including California. He suddenly grasped that these strange and “exotic” rock sequences were remnants of ancient ocean floors that had been lifted on top of the continent through the collision of tectonic plates.

Asilomar Conference Grounds Interior (Erik Olsen)

Moores reasoned that the serpentines and coarsely crystalline igneous rocks at the base of these sequences were characteristic of the rocks underlying all the world’s oceans. The “green rocks” in the middle (now the state rock of California) showed evidence of moderate pressure and temperatures, indicating they had been subjected to significant geological forces. By connecting these ophiolite sequences to the processes of plate collision and obduction (where one plate rides over another), Moores provided a powerful piece of evidence for plate tectonics and offered a new lens through which to understand the complex geological architecture of the American West.

His deduction was in line with what is now known about plate tectonics. The geological “confusion” apparent in the Rockies, the Sierra Nevada, and other western mountain chains was now understood as the result of neighboring plates bumping into each other repeatedly over vast geological timescales. The concept of terranes, foreign rock slabs or slices or sequences that have traveled vast distances and become accreted to continents, further illustrated the dynamic and assembly-like nature of California’s geological landscape.

Fault Activity Map of LA Area in California (California Geological Survey)
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California, situated at the active boundary between the massive Pacific Plate and the North American Plate, became a prime natural laboratory for studying the principles of plate tectonics. The San Andreas Fault, a “right-lateral strike-slip fault” where the Pacific Plate slides northward relative to the North American Plate, is a direct consequence of this ongoing tectonic interaction. Places like Parkfield, California, lying directly on the fault, became the center of the seismic universe, offering invaluable opportunities to study the processes of locking and unlocking that precede earthquakes.

The San Andreas Fault at Wallace Creek. On January 9, 1857, the M 7.9 Fort Tejon earthquake occurred just north of the Carrizo Plain. Here, at Wallace Creek, the fault moved 30 feet (9m), forming the offset stream channel seen in the photo. (USGS)

The dramatic offsets of streams like Wallace Creek on the Carrizo Plain vividly demonstrate the horizontal movement along the fault. These offsets, where streams appear abruptly displaced, serve as clear, visual records of the fault’s slip history, showing just how much the land has shifted over time. Further proof of the movement of plates along the fault was uncovered in a remarkable investigation by Thomas Dibblee Jr., a pioneering field geologist who meticulously mapped vast regions of California. One of his most compelling discoveries was the striking geological similarity between rocks found at Pinnacles National Park and those in the Neenach Volcanic Field, located more than 195 miles to the southeast. Dibblee determined that these formations were once part of the same volcanic complex but had been separated by the gradual (but pretty damn quick in geological time) movement of the Pacific Plate along the San Andreas Fault over millions of years.

The insights gained from the plate tectonic revolution, sparked in part by that pivotal conference in Pacific Grove, continue to inform our understanding of California’s geological hazards and history. The work of scientists like Eldridge Moores and the subsequent advancements in the field have provided a robust framework for interpreting the state’s complex and ever-evolving landscape. The 1969 Penrose Conference marked not just a shift in scientific thinking but a fundamental unlocking of some of the Earth’s deep secrets, with California the place, once again, at the center of scientific advance.

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Long Valley Caldera Discover the Science and Beauty of California’s Ancient Supervolcano

The Legacy of One of North America’s Largest Volcanic Eruptions

The Long Valley Caldera is one of the most active volcanic sites in the United States.
Here, the Owens River flows through it, winding south through Owens Valley. (Erik Olsen)
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Driving up Highway 395 toward Mammoth Lakes is one of the most breathtaking road trips in California. The highway winds through the rugged Eastern Sierra, offering stunning views of snow-capped peaks, alpine meadows, and vast chaparral plains. But beneath this dramatic landscape lurks a hidden danger—an ancient volcanic giant that still stirs beneath the surface.

The Long Valley Caldera in eastern California is an extraordinary geological feature, spanning about 20 miles in length and 11 miles in width. It owes its existence to one of the most dramatic volcanic events in Earth’s history, a supereruption that occurred approximately 760,000 years ago. This event, known as the Bishop Tuff eruption, ejected an estimated 150 cubic miles of molten rock and ash into the atmosphere, far surpassing the 1980 eruption of Mount St. Helens, which released just 0.3 cubic miles of material. The magnitude of the Bishop Tuff eruption resulted in the collapse of the ground above the magma chamber, creating a massive depression known as a caldera. In other words, it’s hard to get your head around how big this eruption was.

The Long Valley Caldera is a striking reminder of Earth’s immense, often hidden, volcanic power and its potential for destruction—located right here in California, near one of the nation’s most popular ski towns, Mammoth Lakes. Geothermal activity, visible in the form of hot springs, fumaroles, and hydrothermal systems, is a constant feature of the landscape. This activity has made the caldera a hub for geothermal energy production, with the Casa Diablo thermal power plant utilizing its subterranean heat to generate electricity. The energy produced at Casa Diablo is enough to power about 36,000 homes, making it an important renewable energy source for the region.

Casa Diablo Geothermal Facility, Long Valley Caldera, California (Erik Olsen)
Casa Diablo Geothermal Facility, Long Valley Caldera, California (Erik Olsen)

The surface of the caldera is also marked by the Bishop Tuff, a layer of welded volcanic ash that provides a vivid record of the eruption’s intensity and the pyroclastic flows that reshaped the landscape. Pyroclastic flows are fast-moving, hot clouds of gas and volcanic material that can destroy everything in their path. Often they are considered more dangerous than the lava that pours forth from an erupting volcano. For example, pyroclastic flows killed far more people at Pompeii than lava, as the 79 AD eruption of Mount Vesuvius unleashed fast-moving clouds of superheated gas, ash, and volcanic debris that raced down the slopes at over 100 mph, reaching temperatures above 1,000°F, instantly asphyxiating and incinerating thousands, while the slower-moving lava played a minimal role in fatalities.

Geothermal features at the Long Valley Caldera commonly support microbial communities of thermophilic bacteria and algae, which thrive in the caldera’s hot springs and fumaroles. These organisms not only influence the terrain by contributing to mineral precipitation but also serve as models for studying life in extreme environments, offering analogs for early Earth and potential extraterrestrial ecosystems. Scientists are just beginning to understand how these bacteria live and thrive in deep ocean vent systems. In some areas around the Long Valley Caldera and Mono Lake, mats of thermophilic bacteria and algae thrive around the geothermal features, like the many hot tubs that dot the landscape, forming colorful, textured surfaces. These microbial communities contribute to the unique environment and can even make the ground feel crunchy underfoot, offering a tangible connection to the caldera’s dynamic, living systems.

The Owens River flows through the Long Valley Caldera near Mammoth Lakes, California (Erik Olsen)

While the caldera’s formation was sudden and catastrophic, its story stretches back millions of years. Scientific studies at the Long Valley Caldera have advanced our understanding of volcanic processes, crustal dynamics, and geothermal systems. The Long Valley Caldera sits within the Basin and Range Province, an area of North America characterized by extensional tectonics, where the Earth’s crust is being pulled apart, allowing magma to rise to the surface.

Using seismic tomography, researchers have mapped the magma chamber beneath the caldera, revealing a layered structure with a partially molten zone capped by solidified magma. This configuration, as highlighted in a 2023 study published in Science Advances, helps explain the periodic episodes of unrest observed in the caldera and provides a basis for assessing potential future activity. Before the eruption, the region experienced significant volcanic activity, with lava flows and smaller eruptions setting the stage for what was to come. Even after the formation of the caldera, volcanic activity continued in the area. Rhyolitic lava flows emerged within the caldera, and the nearby Mono-Inyo Craters volcanic chain has seen eruptions as recently as 600 years ago, underscoring the region’s enduring geological vitality.

Horseshoe Lake in the Mammoth Lakes area, where underground carbon dioxide emissions have caused widespread tree die-off
(Photo: Erik Olsen)

Another place where the region’s volcanic activity can be experienced firsthand is Horseshoe Lake, where carbon dioxide continuously seeps from the ground, suffocating tree roots and causing a vast die-off of trees. The result is a barren, almost ghostly landscape of skeletal trunks and lifeless ground, a stark reminder that Long Valley’s volcanic system is still active beneath the surface. The area is not just eerie but also hazardous—high concentrations of CO₂ can accumulate in low-lying areas, posing a serious risk to humans and animals. Signs around the site warn visitors of the danger, as pockets of odorless, colorless gas can be lethal if inhaled in high enough doses.

Hot Springs geological site near Mammoth Lakes, California. (Erik Olsen)

The caldera has not been entirely quiet since its dramatic birth. Ground deformation studies, using GPS and InSAR technology (satellites), have tracked uplift in the caldera’s floor, offering critical data on magma movement and hydrothermal activity. In a 2016 study published in Geophysical Research Letters, researchers linked changes in uplift patterns to deeper magmatic processes, reinforcing the importance of continuous monitoring. In 1980, a series of magnitude 6 earthquakes occurred along its southern margin, drawing the attention of volcanologists from USGS. These earthquakes were accompanied by noticeable uplift in the caldera’s floor, a sign of magma movement beneath the surface. Since then, the region has experienced periodic episodes of ground deformation and seismic activity, reminding scientists that the volcanic system beneath Long Valley is far from dormant.

Recent research has provided valuable insights into the caldera’s potential for future activity. While there is currently no indication of an imminent eruption, the area is closely monitored by the United States Geological Survey (USGS). This surveillance includes the measurement of ground deformation, gas emissions, and seismic activity, all of which serve as indicators of changes within the magma chamber. The 1980s unrest heightened awareness of the need for vigilance, particularly in regions where volcanic hazards could affect human populations.

Mono Lake is home to thermophilic (heat-loving) and extremophilic (extreme-condition-loving) bacteria. These microorganisms thrive in the lake’s unusual environment, characterized by high alkalinity, high salinity, and elevated levels of carbonate. (Erik Olsen)

As a result of these studies, the town of Mammoth Lakes took proactive measures to ensure public safety. Local authorities constructed an emergency evacuation route to serve as an escape in the event of a volcanic eruption or other natural disaster stemming from the Long Valley Caldera. After local businesses and residents expressed concerns that the original name implied danger, it was changed to Mammoth Scenic Loop to emphasize the area’s beauty and appeal. The United States Geological Survey (USGS) also intensified its monitoring efforts, implementing a color-coded alert system to communicate volcanic activity risks.

Beyond its scientific significance, the Long Valley Caldera is a destination for outdoor enthusiasts and other researchers. Numerous hot springs dot the landscape and are immensely popular among tourists and residents. Mammoth Lakes is one of California’s top recreational spots, providing amazing opportunities to hike and fish during the summer and excellent skiing in the winter months. For geologists, the caldera serves as a natural laboratory, providing an opportunity to study volcanic processes in a setting shaped by one of the most powerful eruptions in recent geological history.

The eastern Sierra reflected in Little Alkali Lake near the Long Valley Caldera (Erik Olsen)

Of course, there remain certain dangers to all this volcanic activity. On April 6, 2006, three members of the Mammoth Mountain ski patrol tragically lost their lives after falling into a volcanic fumarole near the summit. The incident happened while they were conducting safety operations to secure a snow-covered geothermal vent following an unprecedented snowfall. If you’ve ever skied Mammoth before, there is a distinct sulphurous smell around the Christmas Bowl ski run at Chair 3 near McCoy Station.

Steam from an active fumarole near McCoy Station on Mammoth Mountain in 2012. (Flickr)

Standing at the center of the Long Valley Caldera, surrounded by the remnants of a prehistoric supereruption, offers a profound sense of scale and wonder. The vastness of the caldera, framed by the Sierra Nevada and dotted with geothermal vents, creates a landscape that feels alive yet ancient. It’s amazing place to be, both during the day and at night when the stars spread out across the gaping Sierra sky. The ground beneath your feet, shaped by cataclysmic forces, whispers of Earth’s power and the quiet persistence of geological time. Yet beneath the surface, the processes that shaped it continue to evolve, as magma slowly shifts and geothermal systems release heat from the planet’s interior. As research continues and technology advances, the Long Valley Caldera will undoubtedly yield further insights into the intricate workings of our planet’s volcanic systems.

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Laurel Sumac, the Resilient Beauty of Southern California’s Chaparral

Laurel sumac in the San Gabriel Mountains (Erik Olsen)
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Here’s another article exploring some of California’s native plants. With a remarkable abundance of flora, California is home to over 6,500 species that play a vital role in shaping its diverse and iconic landscapes.

While hiking through the chaparral-covered hills of Southern California, from the Santa Monica to the San Bernardino and San Gabriel Mountains, you’ll encounter a rich variety of plants, each adapted to thrive in the harsh, dry conditions. Some of them will inevitably be foreign, as California’s mild Mediterranean climate is a perfect incubator for invasive species. But there are many indigenous plants (aka: endemic) that are touchstones of resilience, survivors that thrive here and help make the California chaparral ecosystem incredibly diverse and hearty. Among these is the laurel sumac, a stalwart of the coastal sage scrub, its waxy, aromatic leaves adapted to withstand the sun-baked hillsides and dry seasons that define so much of California’s natural landscape.

Laurel sumac (Malosma laurina) is a large, rounded evergreen shrub or small tree that can grow up to 20 feet tall and wide. When in bloom (late spring through summer), it gives off a strong, aromatic scent that can be very pleasant. The plant is native to southern California and Baja California, and is also found on the southern Channel Islands.

The plant is characterized by lance-shaped leaves with reddish veins and stems, adding a touch of color to the landscape. Laurel sumac has a unique ability to curl its leaves upward when exposed to extreme heat. This reduces the surface area exposed to the sun, minimizing water loss and preventing overheating. This trait has earned the plant the nickname “taco plant,” as its leaves often fold up like a taco shell. The clusters of small white flowers that bloom at the tips of its branches resemble lilac blossoms. After blooming, the small, creamy-white flowers develop into clusters of tiny, reddish-brown, berry-like fruits known as drupes. Each drupe contains a single seed and is covered with a thin, leathery skin.

From a hike in the San Gabriel Mountains. Most of the large clumpy bushes are Laurel sumac (Erik Olsen)

Although named “laurel” for its resemblance to bay laurel, laurel sumac actually belongs to the cashew family (Anacardiaceae). This family includes other well-known plants like poison oak, mango, and pistachio, highlighting the diverse characteristics within this botanical group. Laurel sumac is a vital species in the coastal sage scrub and chaparral ecosystems, offering habitat and food for wildlife. Its berries are particularly enjoyed by songbirds, including warblers. The plant blooms from late spring to early summer, producing clusters of small, white flowers that attract various pollinators, including bees and butterflies.

After flowering, it produces small, reddish-brown fruits that are a food source for birds and other wildlife. Interestingly, the shrub’s ability to thrive in the arid conditions of Southern California, combined with its distinctive red stems and fragrant blooms, make it a key contributor to the region’s natural beauty and biodiversity.

Laurel sumac along a trail in the San Gabriel Mountains (Erik Olsen)

The plant is amazingly drought-tolerant, with deep roots that allow it to access water during dry periods, making it a critical species in fire-prone environments. In fact, its ability to quickly resprout after fire is one reason it’s so prevalent in chaparral communities.

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Laurel sumac is also notable for its role in traditional indigenous practices. Native peoples of the region used various parts of the plant for medicinal purposes, including treating skin conditions and respiratory ailments. Known as “ektii” by the Kumeyaay people, Laurel sumac held a prominent place in their traditional practices. The Kumeyaay are indigenous to the region that spans southern California, including San Diego County, and northern Baja California, Mexico. After childbirth, a tea or wash made from the plant was used for its soothing and medicinal properties, demonstrating its role in maternal care.

Laurel sumac with its fragrant white blossoms.

Beyond its medicinal uses, the sturdy wood of laurel sumac was utilized in construction, reflecting its practical value to the Kumeyaay. In a modern twist, the dried flower clusters of the plant have found a niche in model railroading, where enthusiasts often paint them and use them as miniature trees to create realistic landscapes.

Laurel sumac is just one of the many incredible native plant species that contribute to California’s rich biodiversity. Its abundance in some of the southern mountain ranges makes it a quintessential part of the landscape and an essential topic when exploring native flora. Stay tuned as we continue to highlight more species that make California such a unique and extraordinary place.

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California’s Dark-Eyed Juncos Are Quietly Evolving in Plain Sight

Dark-eyed junco in Southern California (Photo: Alex Fu)
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When we step outside and see wildlife, we often think of it as unchanging. A bird on a branch, a crab in a tide pool, a lizard skittering across a sidewalk. It feels timeless. But in truth, these animals are evolving, slowly and steadily, right in front of us. As climates become more unpredictable, habitats shift, food sources change, and nature adapts. This is especially true in our cities. Built over just the past few centuries, these sprawling human environments are reshaping the natural world and pushing wildlife to adjust in new and often surprising ways.

As California’s cities have expanded and encroached upon natural landscapes, it turns out the state’s wildlife is adapting in fascinating ways. Studying these changes is central to urban evolution, or how species adapt over time, both genetically and behaviorally, to the unique pressures of city life. From coyotes navigating traffic to birds adjusting their songs to be heard over city noise, urban evolution reveals how nature is not just surviving in cities, but evolving with them. Darwin believed natural selection was too slow to observe in real time, but today we know evolution can happen rapidly, sometimes within just a few generations.

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Dark-eyed junco in Southern California (Photo: Alex Fu)

One cool example of urban evolution in California is the story of the dark-eyed junco (Junco hyemalis), a small songbird traditionally found in mountainous forests that is now thriving in urban environments like San Diego and Los Angeles. If you’re a birder or simply someone who enjoys watching the wildlife in your backyard, you’ve almost certainly seen them. Dark-eyed juncos are small songbirds with distinctive dark heads, often spotted hopping around on the ground rather than perching at feeders. I see them all the time, pecking at the spilled seeds beneath my feeder (or, I should say feeders, as I have several…nerd alert!). It turns out they’re classic ground foragers, evolved to search for food by scratching through leaf litter or snow, uncovering seeds, insects, and other hidden bits.

Recent research has revealed that dark-eyed juncos are evolving in direct response to urban life. Traditionally migratory, these birds once spent summers breeding in cool mountain forests and winters at lower elevations. But in the early 1980s, a group of juncos broke from that pattern and settled year-round on the campus of UC San Diego. There, researchers began documenting striking behavioral shifts. The urban juncos were bolder, less fearful of humans, and had even altered their mating and nesting habits. These changes, observed over just a few decades, offer a vivid example of how quickly species can adapt to city environments, a real-time case study in urban evolution unfolding in human-shaped habitats.

University of California San Diego (Photo: Erik Olsen)

Similarly, at the University of California, Los Angeles (UCLA), a junco population has been thriving for decades, with numbers reaching approximately 300. This long-term success has provided the Yeh Lab at UCLA with a unique opportunity to study how urban environments influence the evolution and behavior of these adaptable songbirds. Their research sheds light on how juncos have adjusted to city life, offering broader insights into wildlife resilience in human-altered habitats.

“It’s impressive how rapidly these vertebrate species can evolve. In a matter of a handful of years, we can find some pretty significant changes,” Pamela Yeh, an associate professor in ecology and evolutionary biology at UCLA, told California Curated. Yeh studied the junco population at UC San Diego when she was an undergraduate student there and wanted to expand the research to the population at UCLA. Studying the two different populations may offer insights into how species evolve in urban environments.

“We want to know, does a city make you evolve?” asks Yeh. “Do the different cities make you evolve similarly? Do the birds all become smaller? Do they all become bigger? Do they all have different-sized beaks? Or is each city unique?”

Dark-eyed junco at UCLA (Photo: Sierra Glassman)

With decades of data, the work echoes the groundbreaking research of Princeton scientists Peter and Rosemary Grant, whose studies of Galápagos finches transformed our understanding of how swiftly natural selection can operate. Now, the junco studies are taking that idea further, showing evolution unfolding not on remote islands, but in the heart of our cities.

“I think it’s now really considered a model vertebrate system for urban evolution,” says Yeh.

In their natural forest environments, juncos breed in response to the changing seasons, triggered by increasing daylight hours and rising temperatures. But in urban areas like those around UCSD and UCLA, where food is plentiful year-round, juncos have begun breeding earlier than normal and throughout the year. They build nests higher off the ground, often on artificial structures, and have increased the number of clutches per breeding season. The availability of artificial light, abundant food from human sources, and fewer natural predators in the city all play roles in these behavioral shifts.

Yeh believes it’s no accident that junco populations have surged on college campuses in recent decades. In fact, she sees it as a direct response to the unique conditions these urban environments provide.

“We think it is is partially that [urban university environments] mimic the natural environment, which is a mix of meadows and tall trees. But the other thing that we think could be important is the irrigation in grassy areas that allow the juncos, even when it’s extremely hot, there are still small insects and worms to grab and feed their offspring.”

One of the most striking adaptations among urban juncos is their behavioral shift in regards to people. Unlike their shy mountain counterparts, urban juncos are much more tolerant of human presence. This is not only a matter of convenience; it’s a survival mechanism. In the city, humans are not a threat, and urban birds need to capitalize on the resources provided by their proximity to people. Their lack of fear “allows them to keep eating even when we walk by,” says Yeh.

Dark-eyed junco in Southern California (Photo: Alex Fu)

Studying junco evolution isn’t just a scientific curiosity. It has real conservation stakes. Things haven’t been looking good for birds. An October 2019 study published in Science by the Cornell Lab of Ornithology revealed that North America has lost nearly 3 billion birds over the past 50 years, with dark-eyed juncos alone declining by 168 million. Yet their ability to adapt to urban life suggests they may have the evolutionary tools needed to weather these dramatic changes.

Beyond behavior, there are physical differences between urban and rural populations of dark-eyed juncos. Urban juncos, for example, developed duller black plumage on their heads and showed reduced white markings in their tail feathers. Yeh and her team have also documented that the wings of urban juncos are smaller, an adaptation likely driven by the demands of maneuvering through a dense, built environment rather than long-distance flight.

Ellie Diamant, currently a Ph.D. candidate in the Department of Ecology and Evolutionary Biology at UCLA in the Yeh Lab, holding a dark-eyed junco. (Photo: Ellie Diamant)

“Juncos historically were migratory birds. The ones that live in the mountains still are. But in the urban environments, we see them year-round,” says Dr. Ellie Diamant, Visiting Assistant Professor at Bard College. “So the benefits are gone for the longer-distance flight, but there seems to be more benefit for these short wings.” Diamant completed her Ph.D. in the Department of Ecology and Evolutionary Biology at UCLA in the Yeh Lab.

The dark-eyed junco is just one example of the broader phenomenon of urban evolution, where species adjust to the challenges and opportunities posed by city life. In California, this phenomenon extends beyond birds. Coyotes, for example, have become fixtures in cities like Los Angeles, adapting to scavenge food from human waste. Coastal animals like sea lions and pelicans have also made urban waterfronts their home, thriving amid the bustle of human activity. Similarly, the Western Fence Lizard has swiftly adapted to life in an urbanized environment.

Junco hatchlings at UCLA. (Photo: Sierra Glassman)

In his book Darwin Comes to Town, Dutch evolutionary biologist Menno Schilthuizen highlights the junco as an exemplar of rapid evolution in urban settings, but it also goes much further, documenting how our manmade environments are accelerating and changing the evolution of the animals and plants around us. Of course, it’s not all good news. Not by a long shot.

Studies published in Evolutionary Applications, underscore that urbanization is a double-edged sword, offering opportunities for adaptation but also introducing serious threats. In Los Angeles, for instance, the fragmentation of habitat by highways has led to the deaths of countless animals, a problem now being tackled through the construction of wildlife bridges like the Wallis Annenberg Wildlife Crossing opening in 2026, designed to reconnect critical migration routes.

Wallis Annenberg Wildlife Crossing currently under construction (Photo: State of California)

The dark-eyed junco’s ability to adapt to city life is both encouraging and a bit sobering. It shows how some wildlife can adjust and find ways to thrive even as human development spreads. But it also reflects the growing pressure we’re putting on natural ecosystems. In other words, it’s not all good, and it’s not all bad. As scientists dig deeper into urban ecology in California and elsewhere, the junco stands out as a clear example of how life shifts and changes in response to the world we’re shaping.

For those of us who live in cities, the juncos flitting through parks, pecking in our yards, and hopping across college campuses offer a chance to see evolution happening right in front of us. Nature isn’t some distant thing beyond the city limits. It’s here, threaded into the daily patterns of urban life.

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All the Fish We Did Not See – The Discovery of the Ocean’s False Bottom off California

A paper nautilus or Argonaut, a group of pelagic octopuses that dwell in the ocean’s twilight zone. (Erik Olsen)
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In the summer of 1942, aboard the USS Jasper, a team of scientists embarked on a mission off the coast of San Diego, California, a hub for U.S. Navy operations and other military activities vital for the Pacific Theater of World War II. Their goal was to test a new technology called “long-range active sonar,” developed to detect enemy submarines—specifically Japanese submarines and German U-boats—during World War II. Long-range active sonar is a technology that sends sound waves through the ocean to map and visualize the seafloor across great distances, revealing details of underwater topography and structures that would otherwise remain hidden beneath the waves.

The expedition was led by Carl F. Eyring, an accomplished acoustic physicist known for his pioneering work in sonar technology. Eyring, along with his colleagues Ralph A. Christensen and Russell W. Raitt, played crucial roles in the mission. Their combined expertise in acoustics, naval operations, and marine science made them the perfect team to explore the deep ocean with sound.

The USS Jasper in 1945—just a few years after scientists discovered the first evidence of the Deep Scattering Layer during a research cruise aboard the ship. (Photo: Naval History and Heritage Command)

As they deployed sonar pulses into the depths, they encountered an unexpected anomaly: a persistent, dense layer approximately 300 yards (about 274 meters) below the surface that scattered their acoustic signals. It was almost as if the ocean floor had risen, looming closer with a strange, unyielding presence that defied all explanations.

This new reading was a complete anomaly, contradicting everything they knew about the seafloor’s topology. It was as though a solid mass had somehow materialized in the depths—a mass dense enough to obscure their sonar and make the familiar landscape unrecognizable. At the same time, their signal strength readings spiked erratically, suggesting significant interference in the water.

Carl F. Eyring (Brigham Young University)

The discovery of this peculiar layer presented an intriguing puzzle to the scientists aboard the Jasper. Yet, with a war raging, they couldn’t afford to lose focus. Instead, they concentrated on measuring its dimensions and mitigating the acoustic interference it created. Determining its true nature would have to wait for another time.

It wasn’t until almost three years later, in 1945, that oceanographer Martin Johnson deployed nets into the Pacific and uncovered the truth: the layer was actually a massive cloud of marine animals, most no larger than a human finger, migrating daily from the deep ocean to the surface and back. This dense biological layer, packed with animals capable of reflecting sonar, had created the illusion of a solid mass, effectively “masking” the true depth of the ocean floor by reflecting sonar waves off the swim bladders of the fish and other marine organisms. 

Bristlemouth trawled from the ocean’s twilight zone (Erik Olsen)

This phenomenon, later termed the Deep Scattering Layer (DSL), created a “false bottom” in sonar readings, revealing an unexpectedly dense concentration of biological life in a mid-ocean zone once thought to be relatively sparse. The discovery of the DSL challenged assumptions about life distribution in the ocean, showing that vast numbers of organisms—such as fish, squid, and zooplankton—populate these depths, rising and descending with daily cycles to avoid predators and optimize feeding.

The DSL is situated within the ocean’s mesopelagic zone, commonly referred to as the twilight zone, which extends from about 200 to 1,000 meters below the surface. This region is characterized by minimal sunlight penetration and hosts a diverse array of marine life. Indeed, this huge swath of biomass is exactly what the sonar was picking up. This remarkable behavior observed in this zone is the diurnal vertical migration—the largest daily movement of biomass on Earth, the world’s largest animal migration. Each evening, billions of organisms (some scientists actually believe they number into the quadrillions) including small fish like lanternfish, hatchetfish and bristlemouths, ascend toward the surface to feed under the cover of darkness, retreating to the depths at dawn to evade predators. (Bristlemouths, by the way, are said to be the most numerous vertebrate on the planet.)

Scattering layer seen on sonar (Erik Olsen)

The discovery of the DSL provided significant insights into marine biology and oceanography. The layer’s composition—primarily swarms of marine animals with gas-filled swim bladders—explained the sonar reflections that mimicked the seafloor. This understanding highlighted the abundance and biodiversity of life in the twilight zone and underscored the importance of these organisms in oceanic ecosystems.

The discovery also led over time to an understanding of the role this layer plays in the carbon cycle, the very phenomenon that helps regulate Earth’s climate. The daily migration of marine animals in this layer is not just a remarkable biological spectacle; it is also a key mechanism for transporting carbon from the ocean’s surface to its depths. As these organisms ascend at night to feed and then return to deeper waters during the day, they excrete waste and many of them die, effectively moving carbon downwards, often sequestering it in the deep ocean floor where it can remain for centuries. This process, known as the biological carbon pump, plays a vital role in mitigating the effects of carbon dioxide in the atmosphere, thus contributing to climate stability. Without the existence of the Deep Scattering Layer and its role in the carbon cycle, the Earth’s carbon balance would be significantly different, highlighting just how interconnected marine ecosystems are with global climate regulation.

In the decades following its discovery, the DSL has remained a subject of scientific inquiry. Advancements in sonar technology and deep-sea exploration have revealed the layer’s dynamic nature and its role in global carbon cycling.

Current research into the twilight zone, particularly by scientists at the Woods Hole Oceanographic Institution (WHOI), is uncovering fascinating insights into this enigmatic region of the ocean. The twilight zone remains one of the least explored parts of the ocean, despite being home to an abundance of life and playing a crucial role in global biogeochemical cycles. Woods Hole has been at the forefront of investigating this layer, employing advanced technology like remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), submersibles, and cutting-edge acoustic techniques to understand its complex dynamics and ecosystem.

One of the leading researchers at WHOI, Dr. Heidi Sosik, has been focusing on the role that the twilight zone plays in the carbon cycle. Sosik’s work involves the use of automated imaging technologies to analyze the behavior and diversity of the organisms inhabiting this region. By documenting their daily migrations and interactions, Sosik’s team has been able to quantify the extent to which these animals contribute to carbon transport. This research is essential for understanding how much carbon is effectively being sequestered from the atmosphere through these daily migrations.

Bristlemouth fish (Erik Olsen)

Another prominent scientist at WHOI, Dr. Andone Lavery, is working to map the twilight zone’s acoustics in unprecedented detail. Lavery’s expertise in underwater sound technology has helped reveal not only the composition of the Deep Scattering Layer but also the behaviors of its inhabitants. Lavery’s recent findings indicate that the twilight zone’s acoustic properties are far more dynamic than previously thought, and these properties can significantly affect how marine animals detect predators and prey, as well as how researchers measure biomass in this layer.

Dr. Simon Thorrold, also from WHOI, has been studying the food web dynamics within the twilight zone. Thorrold’s research has uncovered surprising insights into predator-prey relationships among mesopelagic species. Using chemical tracers, his team has been able to track the movement of nutrients through the food web, revealing that many animals from the twilight zone are integral to surface ecosystems as well, either through vertical migration or being preyed upon by larger species such as tuna, swordfish, and marine mammals.

Scientists use a Triton submersible to explore the ocean’s twilight zone in the Bahamas. (Erik Olsen)

In addition, WHOI has been collaborating with international partners on the “Twilight Zone Exploration” (TZX) project, which aims to better understand how human activities, such as fishing and climate change, are impacting this critical part of the ocean. The mesopelagic zone is increasingly targeted by commercial fishing due to the sheer biomass it holds. Dr. Sosik and her colleagues are actively studying the potential consequences of harvesting these species, considering their importance in carbon sequestration and as a key link in marine food webs.

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Together, these efforts are gradually revealing the twilight zone’s secrets, emphasizing its importance not only in regulating climate but also in maintaining the health of marine ecosystems. As the pressures of climate change and human exploitation continue to grow, understanding this mysterious part of the ocean has never been more critical.

The USS Jasper‘s encounter with the false bottom off California’s coast stands as a pivotal moment in oceanographic history. It not only unveiled the hidden complexities of the ocean’s twilight zone but also bridged the gap between military technology and marine science, leading to a deeper appreciation of the intricate and interconnected nature of Earth’s marine environments.

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Unraveling the Geology Behind Palos Verdes’ Ongoing Landslide Crisis

A neighborhood threatened by landslides at Portuguese Bend on Palos Verdes (Erik Olsen)

For decades, geologists and engineers have been aware that the Portuguese Bend region of Palos Verdes is prone to landslides. Early maps and aerial surveys from the 1930s show continuous movement from the upper hills towards the high cliffs and bluffs that reach the Pacific Ocean.

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Over the years, with a few exceptions, the ground movement was relatively slow, averaging about a foot per year. However, after the intense rains of the past year or two, the land is now shifting much more rapidly—up to 9 to 12 inches per week—plunging neighborhoods and communities built on this unstable terrain into panic and disarray. This accelerated movement has caused irreparable damage to some homes and led California to declare a state of emergency.

Aerial survey from the 1930s showing landslide potential at Portuguese Bend in Palos Verdes (Ranch Palos Verdes city government)

People have been allowed to build homes at Portuguese Bend largely due to a combination of historical oversight, demand for coastal real estate, and limited understanding of the area’s geologic instability when development first began. In the 1950s and 1960s, when much of the residential development in the area took place, there was less awareness and fewer regulations regarding the risks of building on unstable ground. Additionally, the picturesque coastal views and desirable location made Portuguese Bend an attractive area for developers and homeowners. Despite known landslide risks, building permits were often issued because of insufficient geotechnical assessments, political and economic pressures, and a lack of stringent land-use policies at the time. Over the years, as the understanding of the area’s geologic hazards has grown, there have been more restrictions and efforts to mitigate risks, but many homes already exist on land prone to movement.

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The situation is similar to building homes in fire-prone areas – well-known to Californians, of course – within the so-called Wildland-Urban Interface (WUI), where human development meets and mixes with natural landscapes, creating a high-risk zone for natural disasters.

Small landslide at Portuguese Bend in Palos Verdes (Erik Olsen)

Portuguese Bend is one of the most active landslide zones on the peninsula. Here, the earth moves continuously, almost imperceptibly at times, but the effects are undeniable. The land isn’t just sliding; it’s flowing—like a slow-moving river of rock and dirt—down a natural depression, a sort of bowl or gulch formed by the interplay of tectonic activity and erosion. This gradual yet relentless descent toward the sea is driven by a combination of factors: the underlying geology of ancient marine sediment layers, heavy rainfall, and the constant forces of gravity pulling on the steep slopes. As a result, roads buckle, homes crack, and entire sections of land shift over time.

The geological makeup of Palos Verdes is complex and varied. The most prominent rocks on the Palos Verdes Peninsula, and the most crucial in terms of slope stability, belong to the Miocene Monterey Formation, which we wrote about in a previous article. This formation, over 2,000 feet thick in some areas, has been divided into three distinct members based on their rock types: the Altamira Shale, the Valmonte Diatomite, and the Malaga Mudstone, arranged from oldest to youngest.

Portuguese Bend at Palos Verdes

The Altamira Shale primarily consists of thin-bedded sedimentary rocks formed from layers of clay, interspersed with numerous layers of tuff, or volcanic ash that has largely transformed into weak clays over time. Thick deposits of volcanic ash, laid down millions of years ago, have been compacted into a clay-like material known as bentonite. When bentonite comes into contact with water, it becomes extremely slippery, acting like a natural lubricant. This slippery nature has been a major factor in triggering landslides throughout the Rancho Palos Verdes area, where the land’s stability is continually undermined by these underlying geological conditions.

Another factor contributing to landslides is the region’s tectonic activity. Palos Verdes sits above several active faults, including the Palos Verdes Fault. The movement along these faults exerts stress on the rock formations, leading to fractures and cracks that weaken the slopes. These cracks often become pathways for water to seep into the ground, further destabilizing the already precarious terrain.

The road along the coast at Portuguese Point has been moving for decades, a slow but relentless reminder of the dynamic nature of California’s landscape. (Erik Olsen)

Water plays a crucial role in triggering landslides in this region. Heavy rains, especially those associated with El Niño events like the atmospheric rivers of the last few years, can lead to a rapid increase in groundwater levels. When water infiltrates the ground, it increases the pressure within the soil and rock, reducing the friction that holds everything together. In Palos Verdes, where irrigation, septic systems, and urban development are common, human activities can exacerbate this natural process by altering drainage patterns and increasing water saturation in vulnerable areas. This convergence of natural and human-made factors makes the slopes more prone to sliding, particularly during or after intense rainfall.

To combat this, construction teams have installed a series of dewatering wells and pumps to actively extract groundwater from deep within the hillside. By lowering the water table and reducing the amount of water that saturates the soil, these efforts help to decrease the pressure within the slope and mitigate the risk of further ground movement. This method of dewatering is a crucial element in stabilizing the land, as it helps prevent the soil from becoming too heavy and reduces the lubricating effect that water has on the bentonite clay layers.

Closed road at Portuguese Bend in Palos Verdes (Erik Olsen)

Coastal erosion is another critical factor. The rugged cliffs of Palos Verdes are constantly being eroded by the ocean’s waves, wind, and rain. Over time, wave action undercuts the base of the cliffs, removing the support for the upper layers and leaving them hanging precariously over the ocean. As the base erodes away, the upper cliffs become more susceptible to collapse. When combined with the weakened geology and increased groundwater levels, this coastal erosion sets the stage for dramatic landslides.

Portuguese Point cliffs are part of the constant coastal erosion process at Palos Verdes aerial photo (Erik Olsen)

Recent studies are shedding new light on why landslides in Palos Verdes continue to be a concern. Geologists are now using advanced technologies, such as ground-penetrating radar and satellite imagery, to better understand the underground conditions that contribute to landslides. A study from the University of California, Los Angeles, has explored how even minor shifts in groundwater levels, exacerbated by climate change and increasingly unpredictable weather patterns, can tip the balance and trigger significant slope failures. This research emphasizes that it’s not just the obvious heavy rainfall events that pose a threat; subtle changes in water content due to human irrigation, drought, or even slight variations in precipitation can also destabilize these slopes over time.

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Moreover, new geological mapping and subsurface studies have provided a clearer picture of the fault lines and the fractured rock layers beneath Palos Verdes. These studies suggest that the interaction between multiple fault zones may be more significant than previously thought, potentially increasing the region’s susceptibility to movement. Understanding these interactions is crucial for predicting future landslides and developing mitigation strategies.

But in the end, nature will likely have the final say.

Portuguese Bend in Palos Verdes (Erik Olsen)

The picture that emerges from these studies is one of a region where natural geological processes and human activities are in a delicate balance. It’s an ongoing fight that really offers a precarious vision of the future for residents and others who use the area for recreation. The weak rock formations, intersecting fault lines, and relentless coastal erosion create an environment where the land is always moving and on the brink of collapse. Add to this the unpredictable impacts of climate change, which can bring more intense storms and alter precipitation patterns, and it becomes clear why Palos Verdes is so prone to landslides.

Efforts to mitigate the risk are ongoing. Local governments and geologists are working to develop more effective monitoring systems and better land-use planning guidelines to manage development in these sensitive areas. Understanding the complex geology and hydrology of Palos Verdes is critical to preventing future disasters and protecting the communities that call this beautiful but unstable coastline home.

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