In the remote part of the Death Valley National Park, rocks have begun migrating across a flat expanse
of desert. Hundreds of rocks appear to move as a group, as if in a choreographed desert dance. What
could be provoking this strange effect on the rocks in the desert? The prevailing theory has been wind,
but many scientists also advocate ice. A fringe group suggests aliens. I mean it is an isolated stretch of
desert, and everyone knows that aliens love to frolic in American deserts.
Scientists first documented the strange rock movement in 1948. The rocks in question are not tiny. They
range in size from pebbles to boulders. The area where these strange movements are taking place is
called the Racetrack Playa, an area of flat, dried-up region of the desert that was once a shallow lake or
pond. The rocks appear to move en mass in a synchronous motion, including high angle turns and even
reversing direction. Even stranger, some of the rocks inexplicably stop moving for years or even
decades.
Rock Dancing in the Racetrack Playa, Credit: Daniel Mayer
Only recently, the actual rock movement, and thus the mechanism causing the movement, have been
recorded and confirmed. Scientists attached GPS devices to a series of rocks across the playa and set of
multiple stop motion cameras to capture any motion. They also set up a series of equipment to monitor
the weather conditions at the playa.
And then they waited. And waited. And waited. Until . . . weather conditions were just right.
Late in 2013 and early 2014 more than two inches of precipitation fell on the playa forming a shallow
pond. During the night, the water froze encasing the rocks in ice. On sunny, clear days, the ice began to
break up. A light, steady wind gently pushed the ice fragments across the shallow pool of water. The ice
damming behind the rocks and gently nudged them across the playa. In one instance, the scientists
clocked one rock at 16-19 feet per minute. The rock kept up this pace for 15 minutes. As the ice melted
and the water evaporated, the rocks remained in their new position with only a dust trail as evidence of
their former location.
Next time on science mysteries explained – the Nazca lines.
Photo Credit: http://pdphoto.org/PictureDetail.php?mat=&pg=5187