Sailing stones in Death Valley – the extraordinary phenomenon of Racetrack Playa

The dried-up lakebed of Racetrack Playa, located in California’s Death Valley, has for decades been the site of an extraordinary and, until recently, unexplained phenomenon. Sailing stones, whose movement cannot be observed with the naked eye, have fascinated and continue to fascinate both the scientific community and people outside academic circles. Here is the explanation of the mystery that puzzled generations of researchers.

First attempts to explain the phenomenon

The phenomenon has intrigued scientists for many years – the first research was conducted in the late 1940s, and even then long tracks were observed, indicating that stones had moved distances of up to several hundred meters. However, no one had ever seen the process in real time, which came as no surprise – traces of movement appeared only once every few years.

The phenomenon was particularly intriguing because some of the rocks weighed as much as 300–320 kg, and leveling surveys conducted over a 500-meter section where most of the moving stones were located showed a maximum terrain difference of no more than 5 mm. The influence of gravity was therefore ruled out – the rocks could not have rolled down on their own due to their weight.

Numerous hypotheses and no definitive proof

Decades of research brought forth many theories. Scientists considered the effect of strong gusts of wind and speculated about surface runoff. One of the plausible factors that could enable the stones to move was a thin layer of ice forming on the ground. Although studies by geologists such as Robert Sharp and Dwight Carey in the 1960s and 1970s allowed for precise mapping of the stones’ paths, none of the researchers at the time managed to observe the actual moment of movement.

Breakthrough research

It wasn’t until studies conducted between 2011 and 2014 by paleobiologists Richard and James Norris from the Scripps Institution of Oceanography in San Diego that the mystery was finally solved. The researchers installed GPS sensors on some of the stones, which were activated by movement. They also built a portable weather station specifically for the study, which continuously monitored the conditions at Racetrack Playa for several months.

In December 2013, favorable weather conditions occurred: light rainfall covered the playa’s surface with a layer of water that froze at night, forming a thin sheet of ice. During the day, as temperatures rose, the ice began to crack and melt, creating loose, mobile sheets. Thanks to GPS data, researchers determined that the stones began to move along with these chunks of ice, driven by a very light wind with speeds not exceeding 5 m/s.

A simple solution to a complex mystery

The observed movement was slow, as the sailing stones traveled at just a few centimeters per minute. However, it lasted long enough to leave visible tracks. The researchers also recorded video footage of the stones moving in real time, which was a breakthrough in the case and definitively confirmed the hypothesis about the involvement of ice and wind in the process.

The scientists emphasized, however, that the phenomenon can occur only under very specific and rare conditions, which is why it had eluded direct observation for decades.

Sailing stones continue to fascinate

Although the mystery has been solved, Racetrack Playa remains a remarkable place. Due to its unique nature, the phenomenon of sailing stones is nearly impossible to witness with the naked eye. Nevertheless, the entire case shows that, despite highly developed technology, nature can still surprise us – and understanding its mechanisms requires patience, a bit of luck, and humility.