The Racetrack — About a Walk

All interesting walks need not be uphill. Or downhill for that matter. Even almost perfectly level ground can intrigue and astound. For astounding geology and intriguing walks Death Valley is hard to beat - in the correct season of course. In March 2015 I spent a few days in the Valley of Death National Park - not all the time was spent in actual valleys. There are plenty of mountains in Death Valley but there are also areas that vie for the distinction of the flattest places on earth: dry lake beds or playas. Of the many playas in Death Valley, the Racetrack (a very flat but not quite level dry lake bed between the Panamint and Last Chance ranges) is one of the more famous and intriguing geologically. And, in this case, not ancient geology but geology happening right now.

Access to the Racetrack is a bit on the bumpy side with a 30 mile drive on a rough gravel road. No 4X4 required, but take it slow if you're in a passenger car. The road heads south from the Ubehebe Crater complex and crosses a drainage divide covered in Joshua Trees then descends, via Teakettle Junction to the playa. The north end of the playa has a fault block exposed at the surface. The igneous rock weathers into rounded hills and has the dubious name of, "The Grandstand." If the ground is dry, a walk across the playa is easy and surreal.

The Grandstand, Racetrack Playa, Death Valley National Park

On our visit it was a bright sunny day and the sunlight reflected up from the playa floor providing a double dose of solar radiation. There was almost no breeze and the sounds were foot steps on the hard mud crust. It was a grand and intense scene. Taking it all in, making it a place of my experience and a part of my understanding was a thrill for a geology nerd.

One defining characteristic of humanity seems to be the desire to understand our world. That understanding can be on the order of which berries to eat and which animals to be afraid of to the size and contents of the universe or an atomic particle. There have always been, and probably will always be, unknowns or mysteries that we are trying to understand and explain. Of course, real explanations (Science!) are the only ones that truly satisfy. But, the human desire to explain is so strong that when those real explanations are not yet formulated, we tend revert to irrational magical thinking. Which is wholly unsatisfying; for if elves, fairies, angels or other mythical creatures did it, why did they do it and why did they do it when they did? And, by the way, where did they come from in the first place? Why are they here? See? Just more questions. An explanation should reduce the level of ignorance about a topic not create more unknowns.

So, our desire to understand our world makes a mystery very attractive. Mysteries are intensely pursued by the human mind. As evidence, I submit Scooby Doo. If that is not convincing, I will also submit the recently solved mystery of the sliding or wandering stones in the southern portion of Racetrack Playa.

Sliding stones, Racetrack Playa, Death Valley National Park.

The photo above presents the situation. Rocks of various sizes are dislodged from the hillside through first action or possibly earthquakes (Death Valley is very active tectonically). Once on the playa, the rocks slide for long distances across the playa leaving distinct trails of their route across the playa. But, how exactly does that happen? These trails seem much too long for a rock to side along the surface based on the momentum given them from a tumble down the hill in the background. But, their movement is obvious based on the tracks.

Although many people have speculated about how the rocks move (published scientific descriptions and speculations go back at least until 1948), the first time actual movement was observed and documented for science (which means, or at least should mean ALL of us) was in August of 2014. Amazing that something so basic had never been observed. Once again science takes us where no mythology has ever gone before - right to the true explanation. We live in exciting times! The answer is here in a paper published by Norris, et.al. on PLOS ONE.

[As an aside, note that PLOS ONE provides free access to peer-reviewed scientific papers. If you want to get information from previously published papers from the venerable publication The Bulletin of the Geological Society of America, here's what you get: locked out since everything is hidden behind a paywall. They charge the authors a per-page fee to publish in their journals and they charge members an annual fee plus a subscription fee to access their journals. Then they charge the public $25 just to read the article. This is an obscene and antiquated system that relies on the supposed prestige of the GSA to extort money for information. As a member of the GSA I find this embarrassing and appalling. Information must be free in a democratic society and the GSA and many other publishers of scientific research are living in the past. They need to adapt to the new reality and provide their content free to everyone or they will rightfully go extinct.]

A quick read of the abstract of the PLOS ONE article provides the directly observed answer to the mystery: "...the process of rock movement that we have observed occurs when the thin, 3 to 6 mm, 'windowpane' ice sheet covering the playa pool begins to melt in late morning sun and breaks up under light winds of ~4–5 m/s. Floating ice panels 10's of meters in size push multiple rocks at low speeds of 2–5 m/min. along trajectories determined by the direction and velocity of the wind as well as that of the water flowing under the ice." The details of the observations, including placing a GPS unit in a rock and the collection of time lapse photographs are in the report.

Sliding rock mired in the surface of the playa, Racetrack Playa, Death Valley National Park.

There you have it. Direct observation by doggedly persistent researchers utilizing technology to provide answers to the mystery. But, of course there is more than just the explanation. There is the experience of the place and seeing and walking among the results of the phenomena first hand in the sun and dust of a March day.

In the picture above the rock in the foreground seems to have made a nice consistent trail until is apparently sunk into a zone of soft mud and plowed up a barricade to further movement. It appears to be stuck and not likely to move very easily in the future. But, maybe a 90-degree shift in wind direction could mobilize it and send it on its way?

Sliding rock & trail, Racetrack Playa, Death Valley National Park.

I walk along a particularly long arcing trail and imagine the movement of the rock embedded in a thin sheet of ice floating across the muddy playa. It is such a strange thing for a rock to do. Usually they just lie around, maybe fall from an outcrop into a pile of similar rocks. It must be fairly rare for them to go sailing along with the wind.

The largest wandering rock we say at Racetrack Playa, Death Valley National Park

The rock show above is particularly large as you can see by inquisitive humans obligingly providing a reference scale. Perhaps even more interesting is the track in the foreground of the picture. Two tracks come together or a single rock changed direction by 180 degrees. Unfortunately the rock had been removed so I could not figure out what was going on there. Even in supposedly protected National Parks, people do destructive and selfish things.

I'll close with this panorama from the northern portion of the playa near the "Grandstand." The panorama is oriented with north to the left, east in the middle and south to the right. Racetrack playa is an impressive silent piece of geography with wonderfully playful geology. Don't miss it.