A very strange and unsolved phenomenon happens at Racetrack Playa, Death Valley National Park, California where rocks leaves a number and length of tracks.
Sailing stones, sliding rocks, and moving rocks all refer to a geological phenomenon where rocks move and inscribe long tracks along a smooth valley floor without human or animal intervention. Tracks from these sliding rocks have been observed and studied in various locations, including Little Bonnie Claire Playa in Nevada, and most notably Racetrack Playa, Death Valley National Park, California, where the number and length of tracks are notable. At Racetrack Playa, these tracks have been studied since the early 1900s, yet the origins of stone movement are not confirmed and remain the subject of research for which several hypotheses exist.
A CLOSER LOOK:
The stones move only every two or three years and most tracks develop over three or four years. Stones with rough bottoms leave straight striated tracks while those with smooth bottoms tend to wander. Stones sometimes turn over, exposing another edge to the ground and leaving a different track in the stone's wake.
Trails differ in both direction and length. Rocks that start next to each other may travel parallel for a time, before one abruptly changes direction to the left, right, or even back to the direction from which it came. Trail length also varies – two similarly sized and shaped rocks may travel uniformly, then one could move ahead or stop in its track.
The Racetrack’s stones speckle the playa floor, predominately in the southern portion. Historical accounts identify some stones hundreds of feet from shore, yet most of the stones are found relatively close to their respective originating outcrops. Three lithologic types are identified: (1) syenite, found most abundant on the west side of the playa; (2) dolomite, subrounded blue-gray stones with white bands; and (3) black dolomite, the most common type, found almost always in angular joint blocks or slivers. This dolomite composes nearly all stones found in the southern half of the playa, and originates at a steep promontory, 850 ft-high (260 m), paralleling the east shore at the south end of the playa. Intrusive igneous rock originates from adjacent slopes (most of those being tan-colored feldspar-rich syenite). Tracks are often tens to hundreds of feet long, about 3 to 12 inches (8 to 30 cm) wide, and typically much less than an inch (2.54 cm) deep. Most moving stones range from about six to 18 inches in diameter.
A balance of very specific conditions is thought to be needed for stones to move:
- a saturated yet non-flooded surface
- a thin layer of clay
- very strong gusts as initiating force
- strong sustained wind to keep stones going
And in some hypotheses:
- ice floes