Explanation Text : "SAILING STONE"

  Sailing Stone

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.
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.
Preferring mysteries to science
Lorenz's research team calculated that under certain winter conditions in Death Valley, enough water and ice could form to float the rocks across the muddy bottom of Racetrack Playa in a light breeze, leaving a trail in the mud as the rocks moved.
Nonetheless, some visitors to Death Valley seem to prefer more occult explanations for the sailing stones.
"People always ask, 'What do you think causes them to move?' But if you try to explain, they don't always want to hear the answers," van Valkenburg said. "People like a mystery — they like an unanswered question."


 Source :
http://www.youtube.com/watch?v=CjSIjTgrwBQ
http://www.mikesroadtrip.com/tag/death-valley-national-park/
http://www.livescience.com/37492-sailing-stones-death-valley-moving-rocks.html
http://en.wikipedia.org/wiki/Sailing_stones