On Racetrack Playa in California’s Death Valley National Park, stones sit at the ends of long furrows through dried mud. Some trails bend or run alongside others, suggesting that several stones moved together. For decades, the tracks were much easier to find than the movement itself. The result was a genuine physical mystery: identifiable objects had changed position, but the combination of conditions responsible was difficult to witness.
Direct observations and instruments finally documented an ice-driven mechanism during the winter of 2013–14. That finding gives this case a different status from an unexplained apparition or sighting. It is an example of an apparently extraordinary landscape being investigated through measurements, patient observation and competing natural explanations. The remaining scientific questions concern how different stones move under different circumstances, rather than evidence of a paranormal force.
A dry lake with a changing surface
The National Park Service describes the Racetrack as a dry lakebed between the Cottonwood and Last Chance ranges. Rocks reach the surface from the surrounding mountains and leave furrows as they travel over it. The visible cracks and tracks usually belong to the dry phase. They need not show the conditions under which the movement took place. This distinction is fundamental: a photograph of a dry stone and trail is a record of an outcome, rather than a photograph of the driving process.
The landscape is also fragile. The park warns against driving off road and against entering wet playa surfaces, where footprints can persist. Research permits allowed scientific work that visitors should not imitate. Moving a rock to demonstrate a theory would destroy part of the evidence that makes the site interesting. Current road and access information belongs with the National Park Service; the map pin accompanying this historical case is not a route recommendation.
Mapping the evidence before seeing movement
Paula Messina and Phil Stoffer’s 2000 paper, described in the US Geological Survey publication catalogue, reported a detailed survey made in July 1996. Differential GPS mapped 162 rocks and their associated trails with approximately 30-centimetre accuracy. The abstract emphasised a longstanding difficulty: accounts of the tracks were available, but eyewitness observations of the process were lacking, and earlier surveys had covered a more limited area or used different methods.
A mapped track can test whether neighbouring stones followed similar paths and whether movement seems related to the landscape. It cannot, on its own, show the force acting at the moment of movement. Closely parallel trails might suggest some shared agency, while differences might imply independent behaviour. But several physical processes can leave superficially similar results. Mapping made the disagreement more precise without automatically turning a pattern into a unique explanation.
An experiment designed to wait
Richard Norris describes the beginning of the Slithering Stones Research Initiative in 2011 on his Scripps research website. With National Park Service permission, the team established a weather station and equipped fifteen stones with GPS loggers. The intention was to record when stones moved, how fast they travelled and where they went. Norris and his cousin Jim later saw movement in person as the instruments recorded it.
The design addressed the central weakness of an occasional visit. A researcher arriving after a storm could find a new trail but miss the weather, water and ice conditions that made it. A logger left in place could preserve the timing of a short event. A weather station and cameras supplied different kinds of evidence to compare with the recorded motion. The investigation depended on those records agreeing, rather than on the drama of a single photograph.
Scripps’ account explicitly notes that the GPS stones were brought from outside the playa because the park would not permit alteration of native stones. That qualification is easily lost in a short retelling. The instrumented blocks were an experimental sample. Their records were particularly useful when considered alongside observations of the natural stones; they were not a measurement from every boulder scattered across the lakebed.
The winter when the stones moved
The peer-reviewed paper by Richard D. Norris, James M. Norris, Ralph D. Lorenz, Jib Ray and Brian Jackson appeared in PLOS ONE on 27 August 2014. It reported movement during the preceding winter. More than sixty stones moved in an event on 20 December 2013. The observed mechanism involved ice only three to six millimetres thick, light winds of about four to five metres per second, and floating panels pushing stones at roughly two to five metres per minute.
Two instrumented stones recorded movements on 4 December lasting sixteen minutes and covering about sixty-five metres each. The paper combines GPS records, direct observations, photographs and weather measurements. It also reports instrument limitations: some packages flooded, and complete movement records were available for only part of the sample. Those details make the result more assessable. They show exactly which observations were preserved and where the experimental record was incomplete.
Thin ice, modest wind and a large pushing surface
Scripps explains the necessary sequence as a conjunction of conditions. A shallow pond forms, freezes during cold nights, and starts breaking into floating panels when the sun warms it. Wind then moves the ice, which pushes protruding stones across soft mud beneath the water. The observed ice was too thin to lift large rocks off the ground in the way some earlier models had envisaged. The stones were being pushed, rather than carried as floating cargo.
This explains why the site’s association with extreme summer heat could be misleading. The relevant events occurred during a temporary winter pond. It also explains why a modest breeze could matter: the moving ice presented a much larger surface to the wind than an isolated stone. The force did not have to arise from wind striking the rock’s small exposed face alone. Slow movement could also be difficult to recognise without a stationary reference nearby.
A later report of movement without ice
The 2014 observations did not end every argument about every possible movement. In a 2015 Aeolian Research paper, Ronald Jones and Roger LeB. Hooke described Jones’s recollection of stones moving on wet mud in strong wind, without ice. He placed the event in 1972 or 1973, probably in April or May, and described watching by torchlight. The year, season and wind speed were estimates, not contemporaneous instrument readings.
The authors acknowledged that the observation was old and that quantitative measurements had not been made. Their account therefore has a different evidential character from the 2013 GPS records. It is relevant to whether wind alone can sometimes move stones on a very slippery surface; it does not invalidate the recorded ice-driven events. Different conditions can support different mechanisms. A useful explanation should accommodate the quality and limits of each observation instead of forcing them into a single identical event.
What was solved, and what was not
The strongest result is specific: scientists observed and measured stones moving under the action of thin, wind-driven floating ice. That is stronger than demonstrating that a proposed mechanism might work in principle. It connects an explanation with actual motion at the place being investigated. At the same time, it does not reconstruct every old trail or prove that the largest stones always move in precisely that manner.
The distinction also helps with the word mystery. A process can be convincingly demonstrated while its frequency, range of conditions and contribution to older traces remain research questions. Continuing questions do not restore the phenomenon to a state in which no natural mechanism is known. Racetrack Playa remains remarkable because ordinary materials, in an unusual combination, leave a striking and easily misunderstood record.
Sources and further reading
Norris and colleagues, “Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion”, PLOS ONE 9(8), e105948, 27 August 2014, DOI 10.1371/journal.pone.0105948. Primary study, including methods, individual tracks and instrument limitations.
Messina and Stoffer, “Terrain analysis of the Racetrack Basin and the sliding rocks of Death Valley”, Geomorphology 35 (2000), 253–265: USGS catalogue and abstract describing the 1996 mapping survey.
Richard Norris, “Why put a GPS tracker on a rock?”: the investigator’s first-person summary. Scripps, “Mystery Solved: ‘Sailing Stones’ of Death Valley Seen in Action for the First Time”, 27 August 2014: institutional account and interviews with the research team.
Jones and Hooke, “Racetrack Playa: Rocks moved by wind alone”, Aeolian Research 19 (2015), 1–3, DOI 10.1016/j.aeolia.2015.08.001: an explicitly retrospective eyewitness report with stated measurement limitations.
National Park Service, “The Racetrack”: landscape context, conservation and access information. Sources checked 5 November 2026.
Location and related reading
Map note: The pin uses the credited photograph’s documented viewpoint near the southern playa, not the current position of any individual stone or the research instruments. The photograph predates the 2013–14 experiment and illustrates a preserved trail.
Compare the distinction between observations, ground traces and proposed causes in Socorro, 1964, or return to Other Mysteries and the Historical Cases directory.