U.S. route 395 is a geologic master class disguised as a road. It runs north from the arid outskirts of Los Angeles , carrying travelers up to Reno along the eastern flank of the Sierra Nevada. On the way, they pass the black cinder cones of Coso Volcanic Field and the eroded scars of a mighty 19th-century earthquake near Lone Pine. In winter, drivers might see steam rising from Hot Creek, where water boils up from an active supervolcano deep underground. About an hour from the Nevada border, Mono Lake appears, with its bulbous and surreal mineral formations known as tufa towers. Even for someone with no particular interest in rocks, these are captivating, otherworldly sights. But for James Faulds, Nevada’s state geologist, they are something more—clues to a great tectonic mystery unfolding in the American West. If he’s right, all of this, from the wastes of the Mojave Desert to the night-lit casinos of Reno, will someday be beachfront property.
For more than a century, the San Andreas Fault has been considered the undisputed heavyweight champion of large-scale deformation in the West. It is here that the North American and Pacific Plates meet, jostling for position with often violent results. Eventually, the theory goes, the thin sliver of land between the fault and the ocean—from the southern tip of the Baja Peninsula to the Santa Cruz Mountains—will break off from the mainland and slide north, until LA drifts past San Francisco. But there’s at least one problem with this scenario: The San Andreas appears to have gotten jammed. Northwest of LA, near the town of Frazier Park, the fault is kinked out of alignment so dramatically that many geologists suspect the pent-up tectonic strain will have to seek release somewhere else.
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Faulds thinks he’s found the spot. It’s an emerging zone of instability, known as the Walker Lane, that closely follows Route 395. He believes that, over the next 8 million to 10 million years, the North American continent will unzip along this stretch of land, east of the San Andreas. The Gulf of California, which separates the Baja Peninsula from Mexico, will surge north into Nevada, turning thousands of square miles of dry land into ocean floor. (Mapmakers, if they still exist, may label the new body of water the Reno Sea.) While this geologic realignment will take long enough for human civilization to fall, rise, and fall again hundreds of times over, Faulds’ hypothesis is more than an academic curiosity. It represents a radical shift in how geologists use up-to-the-minute tools—satellite data, aerial surveys, computer simulations—to fathom age-old processes. And for residents of the West, it is an invitation to think in an altogether new way about the familiar-seeming ground beneath them. Now is the time: Already the Walker Lane region, with its booming population and burgeoning tech economy, is beginning to feel the rumblings of a new seismic regime.
Many of Faulds’ colleagues dismiss his idea as controversial, fundamentally unprovable, or even simply wrong. It may be difficult to persuade them otherwise: Unlike the San Andreas, which is visible from space, the Walker Lane has yet to form a single, continuous line across the landscape. Still, Faulds has a pretty good idea of where it begins. Using a combination of old-fashioned fieldwork and modern technologies, he is now busily trying to find the rest. Last fall, I drove the nearly 500 miles up Route 395 from LA to Reno to meet him and learn how his tectonic premonition might come to pass.
Faulds picked me up outside my hotel early one morning in a Chevy Tahoe. Strips of neon light cast garish shades of pink and purple over the empty sidewalks. At 61, he bears the boyish expression of a man who remains enthusiastic about his life’s work, who still relishes looking for unusual things in the world around him. We were about to spend a few days hiking through light rain, cold and exposed, and Faulds had come prepared. Laminated geologic maps and layers of warm outerwear were piled high in the back of the SUV, and a generous selection of salty chips and chocolate cookies was stashed behind the driver’s seat.
Our destination that day was a trio of faults near Pyramid Lake, roughly a 35-mile drive northeast of Reno. The three features appear to be related, Faulds said, and seeing them would give me a good sense of how the larger Walker Lane is taking shape. As we headed out of town, he began miming different kinds of fault configurations, rubbing his knuckles together or abruptly knocking one palm against the other. Wrapped up in talk of subduction zones and transform boundaries, he took his hands off the steering wheel for a bit too long and the SUV began to drift. We hit a rumble strip. “Oh, those, uh—they’re much closer to the road here than you think,” he said apologetically. A mile or two later, it happened again.
Although Faulds is now the leading advocate of the Walker Lane hypothesis, he is not the first person to suggest that something big is coming to the region. “There was a lot of work done previously that planted some seeds,” he told me. In the late 1980s, Stanford geologist Amos Nur coauthored a paper speculating that the San Andreas Fault might be looking for a new outlet in the Mojave Desert. Several years later, a strong 7.3-magnitude earthquake near the town of Landers, California, supplied compelling evidence that Nur might be right: Following that quake, a string of mysterious aftershocks rumbled up the Eastern Sierra, illuminating a network of faults that geologists had not previously thought were connected. This was the Walker Lane.
Nur published his paper in the midst of a revolution in geodesy, the study of Earth’s shape and orientation in space. Geodesists make precise measurements of where landforms are at any given moment—mountain peaks, ocean basins, remote islands, entire continents. For them, the planet’s crust resembles an Arctic ice floe, a slow-motion drift that masquerades as solid ground simply because our lives are too short for us to notice the movement. When GPS satellite data was made available to the general public in the 1980s, geodesists saw an opportunity. They began installing fixed GPS monitoring stations, called benchmarks, out in the landscape, then waiting patiently to see how each one moved over time.
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In the 1990s, Nevada received funding from the US Department of Energy to install an unusually dense network of benchmarks in the southwest part of the state. This was not because the feds were worried about the overnight rupture of a new continental margin, but because they were hoping to bury the nation's nuclear waste beneath Yucca Mountain. Radioactive materials were meant to be entombed there for hundreds of thousands of years, and the DOE wanted to ensure the site was safe. (The project was shelved because of political squabbling, though it's resuscitated from time to time.) An unexpected benefit of the new sensor network was that it opened a window on the Walker Lane.
The results were astonishing. GPS stations indicated that only about 75 percent of the tectonic movement between the Pacific and North American Plates was actually occurring along the San Andreas Fault. Much of the remaining 25 percent was bypassing the San Andreas and roaring up the Eastern Sierra, toward Reno, along the Walker Lane. For geologists, it was like discovering that a quarter of the Mississippi River is somewhere out in Colorado.
“Boy, the GPS data really revolutionized our thinking,” Faulds said. Almost overnight, plate tectonics was no longer something geodesists had to speculate about with fieldwork or maps; it had become something they could watch unfold in real time. GPS technology is now capable of recording millimeter-scale changes in the landscape, accurate enough to measure the growth rate of a human fingernail. The past 30 years' worth of data has been breathtaking enough, but in another few decades GPS geodesy is likely to reshape our entire understanding of Earth's crust. Every geodesist I spoke with described the field with a barely contained sense of awe and excitement.
Yet the discovery did not, as one might expect, trigger a surge of interest in the Walker Lane. Scott Bennett, of the US Geological Survey, told me that practically “99 percent of geologists” still consider the San Andreas to be the single most dominant plate boundary in the American West. In this sense, Faulds' idea makes him an outlier. But, Bennett added, just look at a map. The zone stretching away from the Salton Sea, where the San Andreas begins, up into the southern part of the Walker Lane has been quite seismically active of late. Something must be going on there. When I asked Caltech geologist Brian Wernicke, a giant in the field of global geophysics, if it was possible that Faulds was paying too much attention to the Walker Lane, he replied, quickly and without irony: “Well, it's the most interesting place in the world.” In terms of understanding how continents deform and how seismic hazards relate to plate tectonics, he added, “it's an unparalleled natural laboratory.”
As Faulds and I neared Pyramid Lake, he brought up the work of Tanya Atwater, widely considered a visionary in the field of plate tectonics. In the 1980s, Atwater began creating a series of animations depicting the birth and evolution of the San Andreas Fault. They suggest a precedent, Faulds said, for what is happening along the Walker Lane. Early on in the animations, it appears that the modern-day Baja Peninsula is destined to remain a part of the North American Plate; then, at about 7 million years ago, it abruptly cleaves away, creating the Gulf of California. This shift, Faulds said, was largely due to the presence of a chain of old volcanoes on the inland side of the San Andreas. They warmed and softened the continental crust, creating a line of weak spots like the perforations between two rows of postage stamps. That's where the land ripped apart.
An uncannily similar situation may be playing out today, Faulds told me. As you head north from the Gulf of California into the Mojave Desert, an area known as the Eastern California Shear Zone, you pass scores of beautiful old volcanic craters and lava tubes. These features, many of which have become popular hiking destinations, form a line of perforation all the way up the Eastern Sierra, right along the highway that brought me to Reno. “Ultimately,” Faulds said, “what I like about putting all the geological data together like this is that it makes so much damn sense.” I joked that learning about the Walker Lane was like being seismically red-pilled: Once you see it, you can't go back.
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As the North American and Pacific Plates jostle for position, where will the growing tectonic pressure find an outlet?
Pyramid lake is a remote, unearthly place ringed with tufa towers. It is located on a reservation belonging to the Paiute people, who consider it sacred. A mere 13,000 years ago, well within the time frame of human habitation in the West, it was part of an immense inland sea called Lake Lahontan. Since at least then, a series of linear features has been emerging south and west of the current water's edge. These features, known as the Pyramid Lake Fault, the Honey Lake Fault, and the Warm Springs Valley Fault, are almost impossible to see from the ground. They show up clearly in satellite imagery, however, as strange lines cutting many miles through the bare, rolling landscape. Faulds believes they may be on track to connect eventually. “None have become the alpha fault,” he told me. “Yet.”
Faulds and several of his colleagues at the University of Nevada, Reno, have spent much of the past two decades out in the field, attempting to map these evolving faults. In some ways, their work resembles a forensic investigation. With every new crime scene, usually an ancient or recent earthquake, they try to reconstruct what happened. They identify a suspect (in this case, a specific fault) and even establish motive: Why here? Why now? Although today's researchers have voluminous digital evidence at their disposal, Faulds is always seeking tangible proof—proof he can hit with a hammer. He wants to find the faults and folds that he seems named to discover.
After a brief hike around the Pyramid Lake Fault, we headed west into the backcountry toward Warm Springs, where geodesist Bill Hammond and paleoseismologist Rich Koehler were working with a pair of grad students. We found them standing inside a fault trench, a 50-foot-long cut in the ground dug by a backhoe, perpendicular to the fault. It was a kind of diagnostic incision, meant to reveal the layers, or strata, within. One of Koehler's students was flying a drone overhead snapping photos of the trench.
Both Hammond and Koehler work with Faulds at the university, which has quietly become a powerhouse of large-scale tectonic thinking. Hammond, for example, is responsible for much of the geodetic work transforming how researchers understand landscape movement in the American West. When I met him, he was preparing himself and his family for a long sabbatical overseas. “My biggest fear,” he confessed, “is that there will be a huge earthquake while we're gone and I'll miss it.” It would be like a bird-watcher missing a rare hawk he has been waiting his whole life to see. Hammond, who sports curly hair and a lingering grin, is less obsessed with the Walker Lane than Faulds is, though he sees no harm in exploring it as a hypothesis.
Koehler has the laid-back attitude of a surfer, even when he's heavily wrapped in winter layers. When I met him, he was holding a delicate Japanese gardening hoe, which he explained was unusually good for the work of clearing and analyzing the dense strata of sand, gravel, and dirt that mark a fault's history. He crouched and demonstrated his scraping technique. This, Koehler said, pointing casually to a line in the ground, was the fault itself. I looked down and noticed I had one foot placed on either side. For a moment, I caught a glimpse of the vast timescales that geologists inhabit: Millions of years from now, the Pacific Ocean could come roaring through.
In spite of painstaking fieldwork like this and ever-more-detailed geodetic data, reactions to Faulds' work remain mixed. The Walker Lane hypothesis has been criticized as pure speculation, a future scenario that can never truly be tested. Yet for Atwater, the UC Santa Barbara geologist, it is too good not to be true. Laughing with excitement, Atwater told me that, in the past few decades, the tectonic evidence has become simply overwhelming. “It's got to be true,” she said. When I later told Faulds about Atwater's enthusiasm, he actually gasped. “Oh!” he replied, brightening. “Ten years ago, she wouldn't have said that.” Still, Faulds and other proponents of the Walker Lane hypothesis have a lot to prove before their idea goes mainstream.
We left the fault trench at sunset. Deep shadows began to creep across the desolate slopes all around us, the raking light emphasizing the anomalous straight line of the Warm Springs Fault. As the dark band advanced, I had the sensation of watching Faulds' vision come to life—a hidden tectonic presence growing clearer. Yet the route back to Reno, which looped west through California into the red-flaring horizon, reminded me that he still has a challenging problem to solve: Where does the Walker Lane go next? Sooner or later, all these not-yet-alpha faults must reach the Pacific, either through northern California and Oregon or along the bottom edge of Washington state. Nearly as soon as you head west from Nevada, though, the landscape becomes forested. Remote, minor faults like the one at Warm Springs are lost beneath the brush and trees.
That's where lidar comes in. Laser-based radar is a tool of spectacular visual clarity, able to image textures down to a scale of square feet. Like GPS geodesy, it is beginning to revolutionize tectonic research. And because it can penetrate vegetation, exposing features inaccessible to satellite cameras, it accelerates much of geology's grueling fieldwork. Among other things, lidar can pinpoint exactly where a fault trench should be dug.
In the past year alone, high-resolution airborne lidar surveys over Nevada have revealed previously unmapped faults and the remains of ancient landslides. Faulds now hopes to perform further surveys throughout the presumed northern extent of the Walker Lane. When I visited him in his office at the university, he fired up an array of hard-drive-straining data sets. He pointed to the screen, tracing razor-straight lines across the forest floor and the edges of massive debris flows hidden by trees. “Lidar is great for finding previously unknown faults,” Faulds said. “It's hard to get away from those in this area. There are faults everywhere.”
Although a new continental edge won't rip through the American West for millions of years, the risks of a larger-than-expected earthquake along the Walker Lane are real, even today. There could be a high-magnitude temblor while you're reading this very article, but urban officials—let alone residents—seem oblivious to the potential threat. With the exception of Reno and a short list of towns, the region is isolated and sparsely populated. Indeed, it is home to several facilities situated there specifically to avoid contact with human beings, including two enormous depots where the US Army stores explosives and disposes of chemical waste. (An Army spokesperson declined to comment on what the effects of a major quake might be, but assured me there were monitoring systems in place.)
“The problem we have in Nevada is that people assume we're not very seismic,” said Konrad Eriksen, president of Dynamic Isolation Systems, an engineering firm that specializes in earthquake-resistant designs. “Whenever I talk to anybody in Reno, they just go, ‘We're not seismic,’ and I know that's not true.” In 2017, Eriksen said, he and a colleague dug up a map of all the large tremors in Nevada over the past 170 years. Anything bigger than a magnitude 4 is represented with an ominous red circle. Not coincidentally, many of the circles are clustered like a painful outbreak of smallpox right along the Walker Lane, several within driving distance of Reno. “What it shows is that we're highly seismic,” Eriksen told me. “But awareness is very low. Until we have a big earthquake that does damage close to home, that won't change.”
Eriksen's offices are located in the Tahoe-Reno Industrial Center, the country's largest business park. TRIC covers more than 160 square miles—three San Franciscos' worth—of sculpted valleys and rocky hills. Its tenants include Google, Switch, and Tesla, along with 2,000 protected wild horses. TRIC is as sure a sign as any that the Reno area is reinventing itself, aiming to attract younger residents who come not for strippers and slot machines but for lucrative jobs and easy access to the great outdoors. Lance Gilman, the bolo-tie-wearing, larger-than-life businessman behind the development, told me that on his first tour of the land he saw a bird's nest just sitting there on the ground, catching the light. He took it as a good omen, a sign of Reno's impending transition from has-been gambling den in the mountains to tech-centric boomtown. (Still, this is Nevada: At one point during the planning phase, Gilman had to assume management of the nearby Mustang Ranch brothel—the first ever licensed in the state—to stop a biker gang from moving in and marring his glorious vision.)
One of Gilman's employees, a project manager named Kris Thompson, agreed to take me on a tour of the site. We started at Tesla's Gigafactory, which the company claims will be the largest building on the planet when completed. (“It put us on the world stage overnight,” Gilman told me.) Although still under construction, the Gigafactory was already so colossal that I could not make out its scale against the mountains beyond. As we drove on, Thompson directed my attention to the huge stone pads on which TRIC's industrial structures are being erected. “We do not cut corners,” he said. “These pads have no subsidence. We have granite-basalt bedrock. For tech companies, that's great.” (Eriksen seems to agree with this assessment: He and his colleagues have done nothing further to insulate their offices against quakes.) “The lack of a seismic threat in this area is one of our strengths,” Thompson continued.
But, of course, there is a seismic threat. According to Faulds, it's about the same as what I already live with in California. The San Andreas may be closer to the breaking point, but the Walker Lane could see a major earthquake at any time.
Thompson and I returned to TRIC's central office, where Gilman, now walled in by paperwork, was gearing himself up for several hours of new business calls. Last year, a company called Blockchains scooped up 67,000 acres of TRIC land to build a cryptocurrency-powered libertarian city. With that sale, the development had all but sold out. It was time, Gilman told me, to pursue new opportunities. “We're in the path of growth,” he said, as heavy trucks boomed by on the highway, shaking the earth.
“To think geologically,” Marcia Bjornerud writes in her 2018 book Timefulness, “is to hold in the mind's eye not only what is visible at the surface but also present in the subsurface, what has been and will be.” For Bjornerud, a writer and geologist, cultivating an awareness of time spans radically outside of human experience can be meditative, she told me, even spiritual. Being timeful, in her formulation, means allowing ourselves to be daunted by events and landscapes whose scale strains the imagination; it means seeing Earth, and not our own short-lived species, as the main character in the story. For geologists, this is both a necessary cognitive skill and an invigorating intellectual exercise.
When I spoke with Brian Wernicke, the Caltech geologist, he offered an ideal example of timeful thinking. Wernicke believes that the Walker Lane hypothesis is potentially not ambitious enough. He pointed out that over tens of millions of years, the crust beneath Nevada has been stretched east to west so dramatically that it's only about half as thick as it used to be. Like a well-worn piece of denim, it could easily begin to tear. The pent-up stress that currently appears to be migrating from the San Andreas to the Walker Lane might instead be taken up by the Wasatch Fault, which passes through Salt Lake City. In other words, Wernicke said, the Pacific Ocean could someday inundate central Utah.
I relayed Wernicke's idea about the Wasatch Fault to Faulds. After a few seconds of thoughtful silence, he said that one way to think of this would be: What happens after the San Andreas has become a dormant scar in the landscape and the Walker Lane is the definitive plate boundary in the West? Where will the seismic stress go then? Perhaps, he suggested, the Walker Lane will intersect in the far future with Canada's Queen Charlotte Fault, which stretches from Vancouver Island to Alaska. At that point, Faulds told me, you might see the emergence of a genuine megafault, which could begin tearing chunks from North America as far east as Montana. “Maybe that's what Wernicke was talking about,” he said. The two men batted around planet-changing ideas the way other people might discuss the playoffs.
For geologists, seeing the Walker Lane for the first time was like discovering that a quarter of the Mississippi River is somewhere out in Colorado.
This, I came to understand from my trip with Faulds, is what geologists do best—flitting effortlessly between different timescales, combining fieldwork, philosophy, and math into what Bjornerud calls a “polytemporal” vision of Earth. As I'd seen firsthand at the Warm Springs Fault trench, part of what gives geology its power is that its revelations are so easily accessible. You don't always need lidar to help you peer into the gulf between ancient history and the distant future; sometimes it's right between your feet.
In 2007, a seismologist and earthquake historian named Susan Hough published an intriguing essay in a book called Myth and Geology. Hough had become interested in a series of ancient Native American rock carvings in the Southern California desert and along the Eastern Sierra. They show wavy lines, discombobulated human forms, and eerie serpentine figures that likely represent gods. As Hough points out, the sites of these petroglyphs often directly overlap with known faults, raising the possibility that they record earthquake activity. What she does not mention is that almost all of the sites featured in her paper lie along the Walker Lane or its southern continuation into the Mojave. If Hough's interpretation is correct, this would mean that the region's indigenous inhabitants were aware of its growing seismic power for many thousands of years before GPS geodesists came on the scene.
Amos Nur, one of the originators of the Walker Lane idea, told me that cultural evidence of this kind can be easy to miss. A decade ago, he wrote a book called Apocalypse: Earthquakes, Archaeology, and the Wrath of God, about the collapse of civilizations following earthquake storms—devastating sequences of seismic upheaval. In the course of his research, Nur found that historians often overlook ancient earthquakes because written documentation of their occurrence is rare. Yet the physical ruins left behind by these events testify to the presence of catastrophic forces lurking in the landscape. Nur's unsettling conclusion is that earthquake damage throughout human history has been substantially underestimated.
The tools of contemporary geology, including GPS, lidar, computer simulations, and exhaustive fieldwork, have made the Walker Lane visible as never before. But it was there all along, hidden in the region's faults and volcanoes, biding its time. If Faulds is right—if the waters of the Pacific really are inbound north to Reno—then learning to see the signs of tectonic change is both one of the great geologic puzzles of our time and one of the field's most practical applications. The proof of his hypothesis could be one major earthquake away.
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