How a Mystery was Resolved
It was a mystery long in resolving, namely, the “sailing stones” of California’s Death Valley National Park. Sometimes called “walking rocks,” these are boulders as heavy as 100 pounds with one as large as 700 pounds. So, what was the mystery?
Death Valley has a sunbaked lake bed of cracked mud that is flat, flat, flat, and normally bone dry.
Yet, dotting the valley floor are boulders with long grooves behind them cutting through the dried mud. Those grooves indicate such stones have scuttled along the valley floor, sometimes in parallel to one another. This has led some to refer to this area as the “Death Valley race track” or “Racetrack Playa,” with boulders racing one another toward some finish line.
Without any sort of slope to provide a gravity-assisted boost, how have such boulders moved about? For seven decades, folks tried to figure it out. Perhaps high winds nudged rocks along after freak rains soaked the desert floor. Perhaps, during rare periods of rain followed by freezing, the stones skated along on a layer of ice. But, according to calculations by scientists, it would have taken winds in excess of
100 miles per hour to nudge such boulders.
All this was speculation and theory. The stones moved only a foot or so every decade. No one had ever seen them move. That is until a group of determined scientists came along.
In 2011, Johns Hopkins University professor Ralph Lorenz proposed that a combination of forces nudged the rocks. The combination required water, wind, and freezing temperatures that might create an “ice collar” around the sailing stones with “ice rafts,” then pushing them over the valley floor with the assistance of a thin layer of water between ice and mud.
But how to prove the theory? It was often said that watching these sailing stones was like watching rust form on a nail; in other words, impossibly slow for human eyes to detect.
Well, the impossible became possible. In 2011, Richard Norris, a colleague of Lorenz at the San Diego campus of the University of California, set up cameras and weather stations with motion-activated
GPS. Even then, the team believed they might need to wait five to ten years to record any results.
Just two years later, around noon on December
21, 2013, Norris and his cousin James Norris were on hand after the normally dry playa had filled with water. The water surface had frozen overnight, creating a quarter-inch-thick sheet of so-called “windowpane ice.” As temperatures rose, the ice began to break into panels. Trapped within those panels were the mysterious sailing stones. Said Richard to his cousin, “This is it!”
Popping and cracking reverberated across the lakebed, and—in winds as light as 10 miles per hour—sailing stones set sail. Some moved for just a few seconds. Others remained in motion for 16 minutes. But move they did, even if painfully slow by the standards of human eyes. In their wake, they left groves in the mud of the lakebed. At long last, as scientists looked on in awe, a long-standing mystery was resolved.