Research Identifies Mechanism Behind Death Valley's Moving Rocks

For over a century, the movement of heavy rocks across the Racetrack Playa in Death Valley has been observed and studied. In 2014, a research team documented these movements and identified the environmental conditions responsible for the phenomenon.

The Racetrack Playa Phenomenon

Sailing stones, located on a dry lake bed within Death Valley National Park, move across the desert floor, leaving trails that can extend for hundreds of meters. Historical explanations for these movements included strong winds, magnetic forces, and other theories. The mechanism for their movement was unknown until specific environmental conditions allowed for direct observation.

Documentation of Rock Movement

In December 2013, Richard D. Norris and James M. Norris, part of the Slithering Stones Research Initiative, recorded the stones in motion. The team utilized 15 GPS-equipped stones and time-lapse cameras installed on Racetrack Playa.

On December 4 and December 20, 2013, the cameras recorded stones moving at speeds up to 15 feet (approximately 4.6 meters) per minute. One event involved over 60 rocks moving simultaneously across the playa. Some instrumented stones moved distances up to 224 meters between December 2013 and January 2014.

Environmental Factors

The movement of the rocks was attributed to thin sheets of ice, specifically described as "windowpane" ice, measuring 3 to 6 millimeters in thickness. These ice sheets formed during overnight temperature drops and began to melt with morning sun exposure. As the ice fractured, panels, some tens of meters wide, drifted across the water-saturated playa.

Light winds, measured at 4 to 5 meters per second (approximately 9 to 11 mph), propelled these floating ice panels. The ice then exerted pressure against the rocks, causing them to slide forward. This interaction of sun, water, ice, and wind created the conditions for the rock movement.

Rock Characteristics and Track Patterns

Rock shape and surface texture influence the patterns of movement. Rocks with rough undersides tend to produce straight tracks, while those with smoother surfaces create more curved or irregular trails. These tracks can remain visible for approximately three to four years before weathering.

Composed primarily of dolomite and syenite, the stones vary in weight from a few hundred grams to several hundred kilograms. The presence of shallow water and ice on the playa contributes to a low-friction environment, facilitating the movement of even larger rocks with minimal force.