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Sailing stones (also called sliding rocks, walking rocks, rolling stones, and moving rocks) are part of the geological phenomenon in which rocks move and inscribe long tracks along a smooth valley floor without animal intervention.

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. Trails of sliding rocks have been observed and studied in various locations, including Little Bonnie Claire Playa, in Nevada, and most famously at Racetrack Playa, Death Valley National Park, California, where the number and length of tracks are notable.

The Racetrack's stones speckle the playa floor, predominantly in the southern portion. Historical accounts identify some stones around 100 m (330 ft) from shore, yet most of the stones are found relatively close to their respective originating outcrops. syenite, found most abundant on the west side of the playa; This dolomite composes nearly all stones found in the northern half of the playa, and originates at a steep promontory, 260 m (850 ft) high, paralleling the east shore at the south end of the playa. Most moving stones range from about 15 to 46 cm (6 to 18 in) in diameter. Stones with rough bottoms leave straight striated tracks, while those with smooth bottoms tend to wander.

At Racetrack Playa, these tracks have been studied since the early 1900s, yet the origins of stone movement were not confirmed and remained the subject of research for which several hypotheses existed. However, as of August 2014, timelapse video footage of rocks moving has been published, showing the rocks moving at high wind speeds within the flow of thin, melting sheets of ice. The scientists have thus identified the cause of the moving stones to be ice shove.

After extensive track mapping and research on rotation of the tracks in relation to ice floe rotation, Stanley maintained that ice sheets around the stones either help to catch the wind or that ice floes initiate rock movement.

If a sheet of ice around the stones either increased wind-catching surface area or helped move the stones by dragging them along in ice floes, then the rebar should at least slow down and deflect the movement. Two heavier stones were placed in the corral at the same time; one moved five years later in the same direction as the first, but its companion did not move during the study period. This indicated that if ice played a part in stone movement, then ice collars around stones must be small. No stones were confirmed to have moved in the summer, and in some winters, none or only a few stones moved.

They found highly congruent trails from stones that moved in the late 1980s and during the winter of 1992–93. At least some stones were proved beyond a reasonable doubt to have been moved in ice floes that may be up to 800 m (1⁄2 mi) wide. Easterbrook mentions that some nearby rocks having divergent paths could be caused by degenerating ice floes resulting in alternative routes for some stones.

Some GPS-measured moves lasted up to 16 minutes, and a number of stones moved more than five times during the existence of the playa pond in the winter of 2013–14.

Messina, P., 1998, The Sliding Rocks of Racetrack Playa, Death Valley National Park, California: Physical and Spatial Influences on Surface Processes. "Sliding rocks at the Racetrack, Death Valley: What makes them move?". "Origin of playa stone tracks, Racetrack Playa, Inyo County, California". SJSU.edu: "The Sliding Rocks of Racetrack Playa" – by Paula Messina. Earth Surface Dynamics Discussions: "Trail formation by ice-shoved 'sailing stones' observed at Racetrack Playa, Death Valley National Park" YouTube: Moving Rocks of Death Valley's Racetrack Playa – video by Brian Dunning. Plosone.org: "Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion"

Quick Facts

• Trails of sliding rocks have been observed and studied in various locations, including Little Bonnie Claire Playa, in Nevada, and most famously at Racetrack Playa, Death Valley National Park, California, where the number and length of tracks are notable.
• 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.
• Historical accounts identify some stones around 100 m (330 ft) from shore, yet most of the stones are found relatively close to their respective originating outcrops.
• Earth Surface Dynamics Discussions: "Trail formation by ice-shoved 'sailing stones' observed at Racetrack Playa, Death Valley National Park"
• This dolomite composes nearly all stones found in the northern half of the playa, and originates at a steep promontory, 260 m (850 ft) high, paralleling the east shore at the south end of the playa.

Source material: Wikipedia - "Sailing stones". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.