There's something weird going on in Death Valley National Park: these mysterious "sailing stones" are moving across the desert floor, known as Racetrack Playa-- all on their own. For almost a century, scientists were stumped as to how the rocks were able to move, proposing everything from aliens to really, really strong breezes, but with the development of new technology they've started to narrow in on a solid hypothesis. The stones were first discovered in the early 1900s, and people were immediately mystified. The rocks, which range in size from about six to 18 inches in diameter, don't travel in straight lines- they can veer left and right and even move backwards, plus stones of equal size didn't travel equal distances, and to top it all off, no one had ever actually witnessed the stones moving. In fact, each rock generally only moves once every three years, and travels for about ten seconds before stopping. Even with modern equipment, the odds of catching a rock in the act aren't great. A 2011 study proposed the theory that ice floes form around the rocks in certain, very specific conditions, and help the stones slide along the ground when it's muddy and slippery with rain, guided by gusts of wind. A study released in 2013 further bolstered the ice sheet idea by proposing that the narrowing trails left behind the rocks could be related to the lessening amounts of water available in the valley. Also in 2013, several of the stones were reported stolen, which is pretty upsetting, considering some of the rocks were named by researchers. I'm so sorry, Karen, Nancy, and Mary Ann. -Roadtrippers Sailing stones, sliding rocks, and moving rocks all refer to a geological phenomenon where rocks move in long tracks along a smooth valley floor, known as Racetrack Playa, without human or animal intervention. They have been recorded and studied in a number of places around Racetrack Playa, Death Valley, where the number and length of travel grooves are notable. The force behind their movement is not confirmed and is 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 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 the direction it came from. Trail length also varies – two similarly sized and shaped rocks may travel uniformly, then one could move ahead or stop in its track. Most of the so-called sailing stones originate from an 850 ft-high (260 m) hillside made of dark dolomite on the south end of the playa, but some are intrusive igneous rock 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. A balance of specific conditions are 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
