Sailing Stones
In Death Valley, heavy rocks move across the desert floor on their own, leaving long trails. For decades no one knew how. In 2014, cameras finally caught them: thin ice sheets pushed by wind. But the mystery was beautiful while it lasted.
The Phenomenon
What makes the sailing stones so remarkable is the sheer improbability of their movement. Racetrack Playa, located in Death Valley National Park near the Nevada border, is a dry lake bed—a ‘playa’—approximately 3,700 feet in elevation. It is extraordinarily flat, considered one of the flattest surfaces on Earth, and surrounded by mountains on all sides. The playa surface itself is made of fine clay and silt. When wet, it’s slick and muddy, and when dry, it cracks into polygonal patterns. Any movement across this surface leaves visible trails. These trails persist for years, a testament to the ongoing nature of the phenomenon. The rocks themselves are diverse, ranging in size from pebbles to boulders that can weigh over 700 pounds. They originate from the dolomite hills to the south and are washed onto the playa during rare flash floods. Once on the playa, they begin their mysterious journeys. The trails, long furrows carved into the playa surface, some straight, others curved or zigzagging, are undeniable evidence of movement – but how could such large rocks move on their own?
The Setting: Racetrack Playa: A dry lake bed (playa) in Death Valley National Park, located in California near the Nevada border, with an elevation of approximately 3,700 feet and characterized by its exceptionally flat surface and surrounding mountains.
The Playa Surface: Perfect for recording movement: The lake bed is composed of fine clay and silt. When wet, it’s slick and muddy, and when dry, it cracks into polygonal patterns, making any movement across the surface immediately visible.
The Rocks: What moves: The rocks themselves vary in size, ranging from pebbles to boulders that can weigh over 700 pounds, originating from the dolomite hills to the south and transported to the playa during flash floods.
The Trails: Evidence of movement: Long furrows carved into the playa surface, some straight; others curve or zigzag, with lengths ranging from a few feet to hundreds of yards, and different rocks leaving distinctive patterns – all providing undeniable proof that the rocks moved.
The Mystery: What made it strange: No one had ever witnessed a rock moving on its own, the trails appeared without explanation, the heaviest rocks moved just as much as lighter ones, the direction of movement varied, and the phenomenon seemingly violated the laws of physics.
The History of Investigation
The sailing stones attracted attention for a century. Early Observations (1915-1940s): First reports emerged from prospectors and early visitors who noticed the trails left by the rocks, clearly demonstrating that the rocks were in different positions over time. No explanation was available, and the phenomenon was documented but not rigorously studied, remaining a curiosity. Mid-20th Century Study: In the 1940s and 1950s, geologists began investigating the phenomenon, meticulously measuring the rocks and trails, and proposing various theories, but they were unable to capture the rocks in motion, deepening the mystery. The 1970s Research: Researchers named individual rocks and mapped and tracked their movements over years, with some rocks traveling hundreds of yards, but the direction of travel remained inconsistent. Still, no one witnessed the rocks moving. 1990s-2000s: High-tech approaches were proposed, including GPS trackers, but the remoteness of the location complicated research, leading to a proliferation of theories, and the phenomenon gained recognition in books, documentaries, and tourist guides. 2011-2014: The breakthrough came when researchers, led by Ralph Lorenz and Richard Norris, placed GPS-equipped rocks on the playa, set up time-lapse cameras, and patiently monitored conditions through multiple winters.
The Theories
Before the solution was discovered, numerous explanations were proposed. Wind Alone: The obvious initial guess was that Death Valley’s powerful winds could push the rocks, but this theory was quickly dismissed because the winds strong enough to move these heavy rocks would have destroyed the playa surface, and the trails showed no signs of such destructive force. Magnetic Fields: The idea that magnetic or electromagnetic forces could move the rocks was considered, given that some rocks contained iron, but this theory was scientifically implausible, as there was no discernible mechanism for generating sufficient force. Earthquakes and Vibration: Seismic activity was investigated as a potential cause, but the trails showed single movements, not gradual vibration, and earthquakes didn’t explain the phenomenon. Dust Devils: Local wind phenomena, known as dust devils, were considered, but they are brief and scattered, and wouldn’t produce the consistent trail patterns observed. Ice: As early as the 1950s, the theory that ice played a role was proposed. The playa occasionally floods in winter, and ice could form on the surface. However, no one had yet observed the mechanism by which this ice could move the rocks. Hoax: The skeptical position suggested that someone might be moving the rocks as a prank, but this was effectively ruled out because the remoteness and scale of the phenomenon made it implausible, and cameras would have captured any intruders. Extraterrestrial: A fringe theory proposed that alien intervention was responsible, but this was never taken seriously by scientists.
The Solution
In 2014, researchers finally witnessed the movement, thanks to the meticulous work of Ralph Lorenz, Richard Norris, and their team. The Research Team: Ralph Lorenz (Johns Hopkins Applied Physics Laboratory) and Richard Norris (Scripps Institution of Oceanography), along with other collaborators, spent years setting up the experiment. The Method: The team placed 15 GPS-equipped rocks on the playa, installed weather stations and time-lapse cameras, and monitored conditions remotely, returning periodically to check on the progress. December 2013 - February 2014: The conditions aligned during multiple winters: winter rains flooded the playa with a few inches of water, creating a shallow pond. On cold nights, thin ice sheets formed, and on warmer mornings, the ice broke up. Light winds pushed the floating ice panels across the water, causing the rocks to slide along on the slick wet mud beneath. The Movement: As the ice sheets moved, they pushed the rocks ahead of them, resulting in slow movement—inches per second—that was clearly visible and documented by the cameras. The Perfect Storm: The movement required a rare combination of conditions: winter flooding, cold nights, thin ice sheets, sunny mornings, and light winds. What they saw: The rocks moved with their patterns and trails, as documented by time-lapse cameras.
Why the Mystery Persisted
The solution explained why it had taken so long to solve the mystery. Rare Events: The necessary conditions occur only in certain winters, and many expeditions found nothing happening. No Human Witnesses: The movement happens on cold winter mornings, when few people visit Racetrack Playa, and the location is extremely remote, making it difficult to witness. Counterintuitive Mechanism: The mechanism—ice sheets pushing rocks on a layer of water—was not what people expected. Lack of Technology: Earlier researchers lacked the necessary technology, such as GPS trackers and time-lapse cameras. Science as Persistence, patience, and discovery.
The Beauty of the Solution
The explanation not only solved the mystery but also enhanced the awe-inspiring nature of the phenomenon. Elegant Simplicity: The solution, involving ice, water, and wind, was remarkably simple and elegant. Still Rare and Special: The conditions are still uncommon, making the phenomenon worth witnessing. Accessible Mystery: The fact that we now understand how it works doesn’t diminish the wonder. Knowing the answer enhances our appreciation for nature’s creativity and the scale of natural processes. Science as Adventure: The years of research, the remote camping, and the patient waiting all contributed to a satisfying narrative. The rocks are still there. They’re still moving, whenever conditions allow. Their trails are still being carved into the playa surface. Go see them if you can. Stand where the sailing stones rest, look at the trails that stretch behind them, and marvel at a world where boulders journey across dry lakes and nobody knows—until they do.
Visiting Racetrack Playa
The sailing stones are a destination. Getting There: Reaching the playa is an adventure—it’s located in a remote section of Death Valley, accessible by approximately 26 miles of rough dirt road, requiring a high-clearance vehicle (4WD for much of the route). The nearest services are hours away, so self-sufficiency is essential. What You’ll See: You’ll find a vast, flat, cracked lake bed, surrounded by mountains, and scattered rocks with their distinctive trails. Protecting the Site: Visitors are responsible for preserving this fragile environment—do not touch or move the rocks, do not walk on wet playa, stay on designated routes, pack out all trash. Best Time to Visit: Dry season (late spring through fall) is ideal for easier access, but winter visits may encounter flooding or impassable roads, and early morning or late afternoon light provides the best viewing conditions, allowing a full day for the trip. Check conditions before departing.
Sources
- Wikipedia search: “Sailing Stones”
- Chronicling America — Historic US newspapers (1690–1963)