Wednesday, August 27, 2014

Racetrack "Sailing Stones" Witnessed... Mystery Solved!

"Sailing stone" on the Racetrack, Death Valley
In one of the enduring mysteries of the world, people have long wondered how rocks move across a horizontal dry lake bed surface in Death Valley National Park.

People have offered a variety of theories on how the rocks moved, with the first scientific study in 1948 suggesting dust devils.

More recently, high winds were suggested:

Using Differential GPS to Map the "Sliding" Rocks of Racetrack Playa
"So the evidence suggests that strong gusts of wind and swirling dust devils, in combination with a slick playa surface may set even the heaviest the rocks in motion. Off they go, scooting along downwind until friction slows them down and they come to rest. There the stones wait for the next time when slippery mud and wind spur them into action again."

In 2008 Ralph Lorenz of Johns Hopkins University proposed that the rocks moved when embedded in bouyant "ice cakes", as had been witnessed in tidal areas in the arctic.
"The stones partially embedded in the floating ice rise slightly above the bottom with the increasing level of water. Both the friction between the ice and water and between the stones and the bed are very small, so that blowing wind with some intensity pushes the ice (and the rocks embedded). If the stones and mud at the bottom have a light touch, the dragged stones leave a trail that remains once the ice has melted and the water has evaporated."

Would magically energetic rocks look like this when moving?
Having seen many of the prior theories, I offered the following explanation on April 1, 2010:
"Their secret... an internal power source!  They glow as they move.  Who knew?"

My April Fools Day theory didn't gain much traction. It was fun to illustrate though!

Fortunately there were some much more serious people working on the case, so on December 21, 2013, Richard and James Norris were present to see standing water frozen on the lake bed, and to see and hear the ice cracking as the ice started to melt, then wind blew the ice sheet with the rocks embedded.  You can read the full account in today's story in the +Los Angeles Times:

Mystery of how rocks move across Death Valley lake bed solved

I had actually predicted that mode of movement after reading an article on the stones in +National Geographic seven years ago, as I mentioned in this comment on +Flickr:
"I don't believe that 700 pound rocks can move by wind alone; I think they need to be trapped in floating ice, melting along the shore, that far outweighs them and which also catches the wind. Even the heaviest rocks are inconsequential when a solid lake surface that weighs many tons starts shifting in the wind."

I didn't exactly run up there to photograph it... Ice, high winds, while access to the area may be limited, what's not to like about that?   There are some good reasons why no one has been there to see it!

Z truth is out there...
Now that the mystery is solved, will this end the pilgrimage of people wanting to see these rocks, now that the mystery is gone?  The National Park Service worries that the news may actually increase traffic.

Will the end to the mystery stop people from stealing the rocks, with the hope that they have magical powers?

Of course not.  The proposal that the rocks don't have magical powers could simply be a government cover-up, right?  The sale of tinfoil hats to Death Valley visitors will be greater than ever.

Update 7 pm:
Here's a video which includes a sequence showing a rock moving.  Jump forward to 2:58 if you want to go straight there: