Sailing stones
The movement of the rocks occurs when large, thin sheets of ice floating on an ephemeral winter pond move and break up due to wind.
Trail length also varies – two similarly sized and shaped rocks may travel uniformly, then one could move ahead or stop in its track.
[5][6] The first documented account of the sliding rock phenomenon dates to 1915, when a prospector named Joseph Crook from Fallon, Nevada, visited the Racetrack Playa site.
[2] In the following years, the Racetrack sparked interest from geologists Jim McAllister and Allen Agnew, who mapped the bedrock of the area in 1948 and published the earliest report about the sliding rocks in a Geologic Society of America Bulletin.
[1][8] Naturalists from the National Park Service later wrote more detailed descriptions and Life magazine featured a set of photographs from the Racetrack.
In 1952, a National Park Service Ranger named Louis G. Kirk recorded detailed observations of furrow length, width, and general course.
He sought simply to investigate and record evidence of the moving rock phenomenon, not to hypothesize or create an extensive scientific report.
Some stones weigh as much as a human, which some researchers, such as geologist George M. Stanley, who published a paper on the topic in 1955, feel is too heavy for the area's winds to move.
[10] Professor John Reid led six research students from Hampshire College and the University of Massachusetts Amherst in a follow-up study in 1995.
As a result, stones just a few centimeters high feel the full force of ambient winds and their gusts, which can reach 140 km/h (90 mph) in winter storms.
In 2009, development of inexpensive time-lapse digital cameras allowed the capturing of transient meteorological phenomena including dust devils and playa flooding.
The developers of photographic technology describe the difficulty of capturing the Racetrack's stealthy rocks, as movements only occur about once every three years, and they believed, lasted about 10 seconds.
This suggests that this water buoyantly lifts the ice floes with embedded rocks until friction with the playa bed is reduced sufficiently for wind to move them and cause the observed tracks.
The study also analyses an artificial ditch intended to prevent visitors from driving on the playa, and concludes that it may interfere with rock sliding.
[13][14] In 2020, NASA ruled out the potential reasons for the stones moving results from the microbial mats and wind-generated water waves based on a fossil of dinosaur footprints.
Instead, rocks move when large ice sheets a few millimeters thick floating in an ephemeral winter pond start to break up during sunny mornings.
These thin floating ice panels,[17] frozen during cold winter nights, are driven by light winds and shove rocks at up to 5 m/min (0.3 km/h; 0.2 mph).
A statistical study by Ralph Lorenz and Brian Jackson[19] examining published reports of rock movements suggested (with 4:1 odds) an apparent decline between the 1960s–1990s, and the 21st century.
