The Sliding Stones of (Not) Racetrack Playa, and One of the Less Important Consequences of Climate Change

UNR field studies stop on the Carson Sink and Highway 50, circa 1983

There are lots of mystery spots in the world. My garage is one of them. Over the decades it has collected the flotsam and jetsam of our lives, and it hasn't happened in any kind of organized manner. The last few weeks of this summer has seen one of our most ambitious attempts yet to clear out the debris and preserve the important records of our lives. I even had a yard sale! There have been lots of precious little discoveries, and one of them was the snapshot above, of another mystery spot in the world. It was taken in 1983 or 1984 when I was attending grad school at the University of Nevada, Reno.

I know that for some of you, seeing the tracks across the playa surface can only mean one place on the planet: Racetrack Playa in Death Valley National Park. For years and years geologists and others noted the strange trackways made by pebbles and boulders and pondered how in the world they happened. There have been the "boring" scientific hypotheses involving wind, water and ice, and the more exotic fringe ideas like weird magnetic currents and aliens. I took the picture, but I've never been to Racetrack Playa and therefore am not guilty of tampering with the stones (the National Park Service and geologists take a very dim view of such things). It turns out the strange sliding stones have been found in other places. I know of at least three of them.

Paul is going to solve the mystery of Bonnie Claire Playa, no matter the cost.

There seem to be at least three important factors to get sliding stones: a flat playa surface, a nearby source of rocks, and the possibility of freezing windy conditions. The Racetrack has the Grandstand, an island of rock in the midst of the playa and a high enough altitude to get freezing conditions once in awhile. Bonnie Claire Playa in the vicinity of Death Valley has an active alluvial fan and similar elevation. And Highway 50 in the Carson Sink of Nevada has Highway 50. The highway has to cross the playa and to prevent flooding it has been built on a roadway of stones brought in from elsewhere. That's where I was when I snapped the opening picture of this post. Some of the stones escaped from the highway and set off across the playa surface. My fellow students were trying to suggest an origin of the trackways as being the result of high winds and too many drunk geologists being blown across the dry lake surface.

Moving stones on Bonnie Claire Playa

Some hypotheses involved only extreme winds blowing over a very slick muddy playa surface. Some experiments suggested that pebbles could be set in motion by hurricane force winds, but wind by itself cannot explain the fact that some of the moving stones weigh hundreds of pounds. The fact that some rock trails run parallel to each other suggest that they were locked together. A sheet of ice covering the playa provides a possible explanation. It the ice were to break up into smaller sheets, the ice could presumably act as a sail. Most observers figured that high winds were still a necessity.

Stone tracks on Bonnie Claire Playa

In 2013 cameras caught the movement of the stones (see it here). Ice was indeed involved, but hurricane force winds weren't required. The sheets of ice were pushing the rocks around in winds as little as 10 miles per hour. It's not clear if this process can explain the movement of the larger boulders.

The greatest irony of the mystery of the sliding stones is that they might soon no longer move at all. As the climate changes and warms over the coming decades, the required conditions, particularly that of ice formation, will no longer exist.

Here is one more mystery for you. When we last visited Bonnie Claire Playa, we found this circular structure. I welcome any explanation you can provide for this one! UFOs need not apply, even though Area 51 is only a few hundred miles away. You can see some more pictures of the strange feature in my post here: https://geotripper.blogspot.com/2015/02/a-little-mystery-to-accompany-moving.html

Learn more about the research on the sliding stones of Racetrack Playa here:
https://scripps.ucsd.edu/news/mystery-solved-sailing-stones-death-valley-seen-action-first-time

A Little Mystery to Accompany the Moving Stones of the Basin and Range

I'm back from an intense journey through Death Valley National Park and surrounding regions. Much photography and commentary can be expected in the next few weeks, but for today, I'll just lay out a bit of a mystery.

The sliding stones of Racetrack Playa in Death Valley are justly famous, and the mystery of their mode of movement has recently been made clear. But the Racetrack isn't the only place where the stones slide. Bonnie Claire Playa, close to the California-Nevada border, also shows the phenomena. We headed up there on our field studies class. The stones are fascinating, but something else caught my eye while exploring the playa surface.

I don't know what this circle is. It was there by itself, and had no obvious tracks leading to it. Because of its singular nature, I strongly suspect human intervention (SBCC, did you have anything to do with this??). But who knows? If some folks dragged something in a circle, how did they not leave tracks around the edge? Did someone leave a large tire for awhile and retrieve it later?

I even found the circle on Google Earth (below). Again it seems to be all by itself, with no tracks leading to and from.

What do you think is going on here?

One of Geology's Little Mysteries Solved: The Sliding Stones of Racetrack Playa in Death Valley

Bonnie Claire Playa in Nevada

There are side shows that happen in the sciences. There are the big mysteries of the cosmos and earth history that take many years and the work of dozens or hundreds of the greatest minds to solve: atomic theory, quantum physics, plate tectonics, DNA sequencing and so on. In geology, there are the big picture mysteries of how the continents have moved through time, the patterns of evolution of life on the planet, the origins of rock sequences. It's the great human adventure of exploration that carries us into a fascinating future.

And then there are those nagging little mysteries. Why does bread fall with the buttered side down? Why do cats land right side up? It's the kinds of things that have kept the Mythbusters at work for years. Well, it seems that one of those nagging little mysteries in geology has been solved. For years, stones have left mysterious trackways on the surface of Racetrack Playa in Death Valley National Park. They have been noted more than half a century, and have been the subject of a number of studies, but in all those years no one has seen it happen, or provided a convincing explanation of how it could happen. There have been numerous hypotheses, and of course outlandish ideas like magnetic force lines and alien interventions.

Bonnie Claire Playa, Nevada

But now, we are learning that Richard D. Norris, James M. Norris, Ralph D. Lorenz, Jib Ray, and Brian Jackson have shed light on the mystery, and produced digital images of the rocks in action. In their just released article, Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion, they document the conditions that resulted in the movement of numerous stones on the playa, especially during the winter of 2013-2014. The article can be read in its entirety here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0105948 (and thank you for the open access!).

In essence, the researchers marked the location of stones, and outfitted many with GPS trackers. When storms filled part of the playa surface, a thin sheet of ice formed on the water. As the ice began to melt during the day, large sheets of ice were seen moving and pushing the stones.  The winds recorded were not nearly as powerful as expected, as stones were moved when the winds were no more than 4-5 meters per second (9-11 mph). You can see the process happening in the video here:



I was sure all along that UFOs were swooping down and playing a form of ice hockey with complicated rules, but actually the phenomenon the researchers described made good sense. Racetrack Playa is not the only place where rocks have left trails. I've not been to Racetrack Playa yet, but I've seen tracks on Bonnie Claire Playa northeast of Death Valley National Park, and along Highway 50 in the Carson Sink of western Nevada. There were certain factors in common with each site: relatively high altitude, a source of rocks (the roadbed of Highway 50 was one source), and winters that occasionally have freezing conditions and high winds. Ice was suggested as a factor because many of the trails were parallel to each other as if the rocks were locked together.

I've been joking all day that my life feels empty now that the stones have been explained. But does solving the mystery of the sliding stones take away from our sense of wonder at the world? No, it doesn't. It is a marvelous example of how science works. I love to see mysteries solved by good old-fashioned hard work and persistence. 

This also allows me to say to the vandals and felons who have stolen the sliding stones from the surface of the Racetrack, thinking they have some taken possession of a magical key to the supernatural worlds encompassed within: "Guess what, moron! You've stolen a rock. You are an idiot".

Citation: Norris RD, Norris JM, Lorenz RD, Ray J, Jackson B (2014) Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion. PLoS ONE 9(8): e105948. doi:10.1371/journal.pone.0105948