Mystery solved: 'Sailing stones' of Death Valley seen in action for the first time
Rarely formed sheets of ice push rocks across a dry lake in Death Valley. View from the source hill on the south shore of Racetrack Playa. View is looking north on December 20, 2013 at 3:15 pm. Steady, light wind, 45 m/s has blown water to the northeast exposing newly formed rock trails.
Racetrack Playa is home to an enduring Death Valley mystery. Littered across the surface of this dry lake, also called a "playa," are hundreds of rocks -- some weighing as much as 320 kilograms (700 pounds) -- that seem to have been dragged across the ground, leaving synchronized trails that can stretch for hundreds of meters.
What powerful force could be moving them? Researchers have investigated this question since the 1940s, but no one has seen the process in action -- until now.
In a paper published in the journal PLOS ONE on Aug. 27, a team led by Scripps Institution of Oceanography, UC San Diego, paleobiologist Richard Norris reports on first-hand observations of the phenomenon.
Because the stones can sit for a decade or more without moving, the researchers did not originally expect to see motion in person. Instead, they decided to monitor the rocks remotely by installing a high-resolution weather station capable of measuring gusts to one-second intervals and fitting 15 rocks with custom-built, motion-activated GPS units. (The National Park Service would not let them use native rocks, so they brought in similar rocks from an outside source.) The experiment was set up in winter 2011 with permission of the Park Service. Then -- in what Ralph Lorenz of the Applied Physics Laboratory at the Johns Hopkins University, one of the paper's authors, suspected would be "the most boring experiment ever" -- they waited for something to happen.
But in December 2013, Norris and co-author and cousin Jim Norris arrived in Death Valley to discover that the playa was covered with a pond of water seven centimeters (three inches) deep. Shortly after, the rocks began moving.
"Science sometimes has an element of luck," Richard Norris said. "We expected to wait five or ten years without anything moving, but only two years into the project, we just happened to be there at the right time to see it happen in person."
Their observations show that moving the rocks requires a rare combination of events. First, the playa fills with water, which must be deep enough to form floating ice during cold winter nights but shallow enough to expose the rocks. As nighttime temperatures plummet, the pond freezes to form thin sheets of "windowpane" ice, which must be thin enough to move freely but thick enough to maintain strength. On sunny days, the ice begins to melt and break up into large floating panels, which light winds drive across the playa, pushing rocks in front of them and leaving trails in the soft mud below the surface.
"On Dec. 21, 2013, ice breakup happened just around noon, with popping and cracking sounds coming from all over the frozen pond surface," said Richard Norris. "I said to Jim, 'This is it!'"
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Very cool. (pun)
Awesome.
Science reveals things when it's ready, all it takes is time and perseverance.
The second most boring experiment ever?
Not all discoveries are as earth shaking as the "God Particle" thank goodness for curiosity.
I was thinking more along the lines of this:
World's slowest-moving drop caught on camera at last
I live for stuff like this. Very Kool!
Also a good example Steve, thanks for the link.
One of these days I am going to move and a bunch of scientists are going to notice and write a paper. Cool story, Larry.
Interesting....another mystery solved. What's next?
Crop Circles?????????
I'm so glad they finally figured this out! I've wondered about this for years!
What is the pitch of the terrain?
It is pretty flat, since it is the remnants of a salt lake bed. The rocks move with the prevailing wind, just a hair upslope, which was what was so neat about them.
AND the ability to look at something without prejudice and with new eyes. Any time I've made assumptions in my work, I've been an idiot.
Marsha,
We have all done that, and it doesn't make you an idiot... it makes you human.
Dearest Perrie, in geology, any time you know, in your heart, what something is, (without doing the proper leg work), it isn't. We all look for patterns. When something is an anomaly, we're still trying to fit it into a set pattern... And then, there is that one well boring, that blows it all away...
I once drilled a test well, 20' from a test well. Both the driller and I looked at each other in utter disbelief-- the formations were like they were upside down. We had tentatively designed a test pumping well, based on that one Wonderful test well. 20' from the wonderful test well, the formation was utter and complete crap. Restart!
My dear Royal Lancer, the feeling is entirely mutual!
(((((((((((((((Royal Lancer))))))))))))))))
You are absolutely one of the kindest people I know. May I say that it is an honor and a privilege to know you? Because it is.
Many adjectives could be used to describe you Marsha but "idiot" isn't one of them!!!!
Sweet Larry, I feel that way about myself when I miss something I should have thought of. Thank you, so very much, for your kind words!