Death Valley's Sailing Stones Caught In the Act

Capt.Albatross (1301561) writes "The flat surface of the Racetrack Playa in Death Valley is littered with rocks, some weighing hundreds of kilograms, each at the end of a track indicating that it has somehow slid across the surface. The mechanism behind this has been the subject of much speculation but little evidence, until a trio of scientists caught them in action with cameras and GPS."

From TFA:

[Dins]

Jagged plates of thin ice, resembling panels of broken glass, bulldoze the rocks across the flooded playa, the scientists reveal today (Aug. 27) in the journal PLOS One. Driven by gentle winds, the rocks seem to hydroplane atop the fluffy, wet mud. "It's a wonderful Goldilocks phenomenon," said lead study author Richard Norris. "Ponds like this are vanishingly rare in Death Valley, and it may be a decade between heavy enough rain or snowfall events to make a substantial pond," said Norris, a paleobiologist at the Scripps Institution of Oceanography in San Diego, California.

Re:From TFA:

[Anonymous Coward]

That's the digested version of the actual article in PLOS One [plosone.org], which isn't paywalled.

One of the coolest parts is the way they instrumented "test rocks" with GPS that could stay powered for very long durations (months/years) from a small battery because of how intermittent the movement is and how remote the location is. The trick was not to engauge the GPS data logging until a magnetic switch was tripped when the rock moved. The magnet was set in the floor of the playa lake, the switch in a hole bored in the rock that also contained the GPS receiver. The instrumented rocks were brought in for the experiment and behaved the same as the natural ones on the site.