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The mystery of the sailing stones has been solved!
For years, enormous stones have been moving across the Racetrack Playa
of Death Valley National Park, leaving engraved trails in the muddy
surface behind. No one understood how, though there was plenty of
speculation, according to researchers at the Scripps Institution of
Oceanography at University of California San Diego.
Last year the researchers, Richard Norris and James Norris, placed
stones equipped with GPS devices on the same stretch of land, then
waited and watched.
"We recorded the first direct scientific observation of rock movements
using GPS-instrumented rocks and photography, in conjunction with a
weather station and time-lapse cameras," the authors wrote in a study
published in the journal PLOS One.
On Dec. 20, 2013, they witnessed 60 rocks move across the land.
They discovered that the very thin ice that trapped the rocks during
winter melted in the midday sun, and then the ice and water and rocks
were all blown by wind, making it seem as if the stones moved by
themselves.
"In contrast with previous hypotheses of powerful winds or thick ice
floating rocks off the playa surface, the process of rock movement that
we have observed occurs when the thin, three to six [millimeter],
“windowpane” ice sheet covering the playa pool begins to melt in late
morning sun and breaks up under light winds of (about four to five
meters per second)," they wrote.
Article source: ABC News
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