Mystery Archive / Observation & interpretation
Death Valley’s Moving Rocks: What Happened Behind the Tracks?
Long trails remain behind stones on a flat lakebed. How is seeing a track different from recording the conditions of movement?
First, what are these moving rocks?
At Racetrack Playa in Death Valley National Park, USA, long trails extend behind stones on a flat lakebed. They look like marks left by dragging rocks across the ground. The usually dry setting made the timing and cause of movement a lasting puzzle.
This does not mean the rocks walk by themselves. A trail is evidence to investigate, but it cannot preserve every condition around the stone while it moved.
In the winter of 2013, researchers directly observed movement and recorded it with instruments. They documented a process involving shallow water, thin floating ice and wind. We explore what those observations added to the tracks.
How is a record of a stone’s path different from evidence of what moved it?
Begin with the long trail behind the rock
A playa is a dry lakebed. At the Racetrack, stones sit beside elongated trails in the ground. A familiar dry desert view does not mean that conditions remain unchanged throughout the year.
The trail provides clues about a route. It does not, in one scene, preserve everything about rainfall, ice or the wind at the time.
A visible path does not show every cause
A stone and its trail invite us to imagine the journey. Yet seeing a final position and a route is different from observing what touched the stone while it moved.
The connected lab’s first stage displays only positions and a path. Scrubbing the invented scene moves the stone, while its surroundings remain unspecified. That difference is our starting point.
A Remaining Track and Conditions to Investigate
Instruments were set up to wait for movement
In winter 2011, the permitted research project installed GPS-equipped stones prepared for the study and a weather station. The team could then monitor both position and weather while waiting for a rare event.
In December 2013, researchers saw stones moving at the water-covered playa. Observations during motion could now be considered alongside studies of the trails left afterward.
Water, thin ice and wind acted together
In the observed process, a shallow pond froze at the surface during cold nights. As the ice melted and broke apart during the day, wind-driven panels pushed stones across the wet bed, leaving trails.
This differs from stones floating on thick ice rafts. The recorded motion involved thin ice pushing stones, rather than an explanation relying only on exceptionally strong wind.
- Monitoring equipment is installed
A permitted study deploys GPS-equipped stones and weather instruments.
- Movement is observed and recorded
Researchers directly observe and record movement during winter water-and-ice conditions.
- The findings are published
On August 27, PLOS ONE publishes the study combining direct observations and instrument records.
Read position and surrounding conditions together
The 2014 paper brought together position records, photographs and weather observations. These offered a more specific account of conditions during movement than a trail alone could provide.
The study did not measure every stone or every trail from the past. Keep the explanation supported by observed events separate from questions that individual older tracks would still require us to investigate.
Separate the remaining track from missing conditions
This is a story about an intriguing trace gaining a more specific explanation through observation. Rather than discarding the trail, we add information about the circumstances in which it formed.
In the lab, move an original drawing of a stone along an invented route, then reveal water, ice and wind. The layout and sequence were designed for explanation. They do not replay research footage or measured data.
What can we add to a scene showing only a trail?
Scrub the invented positions, then explore an explanatory sequence showing water, ice and wind.
Explore the rock and its conditionsSources and scope
We consulted the National Park Service, the research team’s account and the original 2014 paper. These sources partly describe the same observational study; they are not three independent experiments. Follow the source links for field photographs and footage.
- 01The Racetrack US National Park Service · Death Valley National Park · Checked 2026-10-22
- 02Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion Norris et al. · PLOS ONE (2014) · Checked 2026-10-22
- 03Mystery Solved: “Sailing Stones” of Death Valley Seen in Action for the First Time Scripps Institution of Oceanography · UC San Diego · Checked 2026-10-22
The text and diagrams are original. Rock shapes, paths and the scene sequence are invented examples. The lab does not calculate or present measured water depth, ice thickness, wind speed or rock speed, nor does it establish an equally complete explanation for every older trail.