Travels in the American Southwest
Sliding Stones of Racetrack Playa
GPS N36° 39' 59", W117° 34' 02"
38 miles south of Ubehebe Crater, Death Valley, CA
Road factor/Accessability - very pitted, dirt/gravel
~230 miles from Las Vegas

NOTE: After passing Ubehebe Crater, the road to the Racetrack Playa becomes more suited to 4 wheel drive vehicles with higher clearance than passenger cars. Extreme caution is advised.

When you pass Teakettle Junction, you're almost to the racetrack. You'll know it's Teakettle Junction by the teakettles left hanging on a signpost's crossarms. (That is unless  Ranger Dan (in his National Park Service humvee) has removed them yet again because "it's against the law to leave them there".)

Off to your left, you'll soon see a large expanse of playa. Don't stop here because the phenomenon you're looking for is another eight miles further down the road. You know you've arrived when you see the sign placed by the state of California detailing the story of the Sliding Stones of Racetrack Playa. As you look over the perfectly flat playa, you can't help but notice what looks like long trenches gouged in the rock hard dry pan.

   

The trenches zig-zag back and forth showing no rhyme nor reason for their paths. At the end of a trench, more often than not, is a large chunk of Cambrian dolomite. These are the famous Sliding Stones of Racetrack Playa, also called the Sliding Rocks, Moving Stones and even Sailing Stones of Racetrack Playa. The rocks, ranging from a few ounces to hundreds of pounds, appear to have slid across the playa leaving clearly discernible paths in their wake. These paths go on for hundreds of feet with the longest path recorded at over 660 feet! It's obvious that something has pushed the rocks but there have been no first-hand observations of the rocks in motion.

A group from the California Institute of Technology (D. Bacon, T. Cahill, and T.A. Tombrello) has investigated these strange rocks and their trails. These scientists measured and weighed many of the rocks. They determined things like the "threshold coefficients of static friction" and the composition of the playa surface (smooth/coarse consistency).

After an exhaustive review with thousands of measurements taken and equations developed, they determined that because the playa was extremely flat and smooth, adding water from runoff and pooling from rain produces an extremely slippery surface. Due to the topography of the southern area of the playa, wind speeds of 70 mph and greater are caused by the wind channeling through the large dolomite ridges bordering the playa. In short, the wind appears to be responsible for this strange phenomenon.

It was determined that rocks break off of the dolomite ridge and roll down onto the playa. Under the influences of the wind when the playa surface is saturated, the rocks are propelled across the slick surface leaving an easily observable path behind.

The scientist's paper - Sailing Stones on Racetrack Playa - can be found in the Journal of Geology, 1996, volume 104, p.121-125.  A copy of their paper is provided here through the courtesy of the Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA.

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