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The Sliding Rocks of the Racetrack Playa Mystery Answered

"One of the most interesting mysteries of Death Valley National Park is the sliding rocks at Racetrack Playa (a playa is a dry lake bed). These rocks can be found on the floor of the playa with long trails behind them. Somehow these rocks slide across the playa, cutting a furrow in the sediment as they move. "

The Question remains: "How do they move?"



Could it be a combination of the theories, not necessarily a strong combination, but include the possibility of magnetic fields?

Sorry, but I haven't checked in for some time. The stones of the playa do not contain iron, and are not subject to magnetic fields. Ice sheets can't explain the splash patterns, and wind does not blow rocks uphill. The only realistic explanation is frost heave. The stones are sliding downhill.

The reason the rocks move is due to a common phenomenon known as frost heave. Ice lenses form beneath the surface creating slopes for the rocks to slide down. Any rainfall that occurs while ice lens formation is present is enough to set the rocks in motion. The frozen subsurface explains why stones leave a uniform depth of track no matter how much they weigh.


Mud on ice is VERY slick.

Just out of curiosity, Mr. Berger, are you just posting your theory to every single site with reference to the Racetrack Playa?  And posting as though it were a "known fact" rather than your own personal guess?

I came up with this idea more than 20 years ago. Before I joined the debate, I decided to attack my own hypothesis trying to disprove it. I didn't want to look foolish if it was totally impossible, but I didn't succeed. Trying to get my hypothesis heard by anyone has become quite frustrating, so I started posting on blogs just to get my opinion heard. As for peer review, try getting anyone to even listen when you don't have a degree. I decided maybe it was best if I posted it as factual, and wait for people to start attacking it. When they wind up in my position of not being able to disprove it, maybe I'll make more headway. Please accept my invitation to be the first attacker, and good luck.

Mark B.
Greenville, OH

20 years ago?  You can certainly get good science published in peer-review without a degree.  I have examples which I can provide if necessary, but they are not pertinent to this issue.  If you have a good hypothesis, with good quantitative data to back it up, then you can definitely get it published.

What you are doing is not even close to the way science works.  Any crackpot (which you probably aren't) can come up with a hypothesis or three, then tell the community "now you have to disprove what I've said, or I must be right."  It is your responsibility to provide evidence supporting your hypothesis, and to outline observations or measurements which could be made, but have not, which would either support or refute your hypothesis.

Have you actually seen, or have any literature citations to support, permafrost in the Mojave desert?  Or even the kind of solid below-ground freezing necessary for frost heave?  Such data would go far to supporting your hypothesis as plausible.

I did not decide to join the debate until recently, and to be frank, I questioned myself as to how some nobody in small town Ohio could come up with a viable hypothesis when so many had been looking for so long. That is why I did a full scale attack against my own idea. I did not want to look the fool. As it stands now, I would love to have the opportunity to do a single core sample at the southern end of the playa. First to verify that a supply of water is available below the surface, and second to subject the soil to the Casagrande criterion. Passing both tests would mean it is not a matter of if it could happen, but only a matter of when it wil happen. That science is already recognized and understood. Unfortunately, I do not have the resources to do that. I would greatly appreciate any suggestions or advice you might have.

Thank you for your time,
Mark B.

(kelseyMH - apologies for butting in)

Ummm. It's not a good idea to assert as fact something which has absolutely no evidence backing it. I don't mean evidence that's questioned, or evidence that's been discarded, or evidence that's in controversy, or evidence that not everyone accepts - like you said, you don't have any evidence. At all.

So, setting aside the question of evidence for a moment, what do the arguments against your own hypothesis look like? What's it look like when you play devil's advocate?

When playing devil's advocate, I looked at wether frost heave could actually overcome the fact that the southern end of the playa is a few centimeters lower, because the minor amount of expansion caused by ice in soil simply could not generate the amount of upheaval necessary to bring about a sliding event. I researched frost heave, and discovered ice lens formation. I didn't think that the weather could get cold enough for frost heave, but a PBS show said it best, some times hell freezes over. The fact that the surrounding terrain features shield that area of the playa from the sun in the winter did not help my advocacy. In order for ice lens formation to occur, you need the right soil type, and a supply of water. A silt clay sediment mix is highly conducive to ice lens formation, and there are springs near that end of the playa. Every time I tried to argue against my own idea, I found more reason to believe it. I saw a picture of mud clumps that had slid across the surface, and you could still see faint traces of a fracture where they originated. Exactly the same way that frost heave tears up roads in Ohio. When I got to the point that not only can frost heave overcome the fact that the southern end of the playa is a few centimeters lower, it might actually be the reason it is lower because the surface layer of the playa is washing away as well, I gave up and started believing myself again.

It is still the case that you have a vague hypothesis, not an "answer", and it will remain a hypothesis until you (or somebody else) goes to the Playa to test it, or until a better hypothesis replaces it.

In this case, your "frost heave" idea is attractive, but you have not presented a mechanism whereby the frost will consistently "heave" on the SSW of the rocks (I can think of a mechanism that will produce a general tendency, but not a consistent pattern - can you?).

The available data supports the wind-blown hypothesis, not the frost-heave hypothesis, so the accepted hypothesis is "wind", not "frost".

This is nothing to do with popularity (science is not a democracy), but with evidence.

You have previously dismissed the wind hypothesis out of hand - would you care to present the evidence you possess that contradicts the wind hypothesis, or fits the available observations more accurately?

Hmm, when you go to the site itself, the picture to the right of the main page shows the rock actually digging a trench as it moves, with loosened dirt on both sides of the rock.  Wouldn't wind disperse this ? 

The wind theory, as well as mine, relies on the idea that the playa surface is wet when the rocks move. The loosened dirt on either side of the trail would not be greatly affected by the wind. It is, however, one of those points that lead to eliminating the ice sheet idea.

hmmm, yeah, the dirt may be "damp" but where the rock pushes it aside, it looks very "powdered" and further wind, should dry out and move it I would think....

but, who knows eh?  :-) 

It is a silt clay mix that is not susceptible to wind erosion as much as a fine powder would be, but the tracks don't last forever.

I find it a bit hard to swallow that the rock is moved by the wind but the dirt is not.....but again, I am not familiar with the conditions, not having seen it up close and personal, like.

The clay grit you find in the Mojave and other parts of the California High Desert is really yucky stuff.  When it's completely dry, it's either hard-as-rock solid (you can land a plane on it), or a fine dust (as fine as talc, sometimes, and gets into everything :-( ). 

Get it wet, and it doesn't act like mud, but more like grease.  It form an opaque viscous layer that a professional skater would be hard-pressed to walk on without falling down.  I hatedloathed despised the stuff when I had to deal with it during one summer.

I can imagine it being slick enough to support having a high and steady wind push a rock a few millimeters or centimeters at a time.  Some of the recent published work, however, indicates that the measured coefficient of sliding friction is still too high, especially for the larger rocks.  So I think now that the jury is more out than when I first read the USGS papers.

I wonder if it has a lot of graphite in it?  That would certainly make for a hard dried surface, but also a slicker one when damp since, as you know, graphite is used in some lubricants.

The USGS papers were probably written by some intern who did a little research and posted the idea that wind was blowing rocks uphill without the paper being thoroughly examined by an actual scientist/geologist. There are other studies that absolutely refute the possibility, because the coefficient of friction is too great for the wind to be the source of movement. I think it was back in the 60's that a geologist named Creutz said that gravity acts on rocks. His theory was totally dismissed by the wind theorists when he observed a rock trail that stopped, and turned almost 180 degrees in the opposite direction. They dismissed his theory entirely, but the wind theory did not explain it either. The sad part of it is that the wrong theory was dismissed.

You may have a valid point there because the studies that said the wind might be capable of moving some rocks were taking into account what would be tornado force winds. You would certainly be able to expect that there might even be scouring of the surface under such extreme conditions. The problem with the wind theory is that the surrounding terrain features have to channel the wind so that it is strong enough to move the rocks, thus the general NNE direction of movement. What it can't explain is why the rocks sometimes go the other way.

I am not saying that ice lenses consistently form to the ssw of each individual rock. What I am suggesting is, that entire area of the playa is capable of forming a single incredibly massive ice lens, and it  is by no means any stretch of the imagination. I live in Ohio. Our building codes require that the footers for house foundations have to be at least 3 feet down. In Maine, it's 6 feet. Frost heave is so common, building codes have to take it into consideration.The reason for that is to get the footing below the freeze thaw boundary. It is the freeze thaw boundary that generates ice lenses. The southern end of racetrack playa, because of the springs that are there, because the surrounding terrain features shield it from sunlight in the winter, because the soil type is optimal, and perhaps even because the wind is channeled through that area, is nothing but an ice lens generating machine. It is not even a question as to IF they are going to form, it is only a matter of when.

I forgot to include that, (was it Sharp and Carey ?) did tests on the playa surface that concluded that wind alone was not capable of moving the stones. The coefficient of friction was far to great for wind to overcome. I believe it was something like a 250 MPH wind necessary to move the heaviest  rocks. They were looking at the possibility that ice sheets surrounding the stones were increasing the wind"s effect by creating a larger contact surface for the wind to react with. Either way, each hypothesis has serious holes. Wind alone can't move the rocks. Ice sheets around the rocks do not accomodate the fact that the trails exhibit splash patterns. I have studied this extensively, and movement by wind just doesn't make sense. I did not dismiss anything out of hand, I used reason to eliminate each hypothesis. The latest from Paula Messina is that microbial organisms that exist on the surface of the playa, at certain times, are responsible for turning the surface into something slicker than Teflon. I am suggesting that rocks slide downhill because of a phenomenon so common you can't build a house in Ohio without taking it into consideration.

A gentle wind can gently wobble to rocks - enough to shift grains of sand and soil and shift the rock forwards.

It is quite disingenuous to dismiss "wind " on the grounds of too much friction, then claim that your own idea is right because you have found a way of accounting for the friction.

The conditions on the Playa are radically different to Ohio.

I suggest you find some evidence to support your idea.  Flights are quite cheap at this time of year...

Last year, my wife had a heart attack. From personal experience, I can tell you that having to do CPR on your own wife is something you NEVER want to happen. Even with insurance, the medical bills were rather expensive, so I simply cannot afford to take off. As I said in a prior post, I just don't have the resources.

As for wind moving the rocks, let's say hypothetically that yesterday, 1,000,000 rocks on the face of the planet moved because of natural forces. Of those 1,000,000, gravity played a role in moving 1,000,000 of them. I am not arguing the extreme point here, I think YOU need to go find evidence that wind can move a rock.

I have already attempted to contact several members of the USGS, and the only response I received was from Angela Jayko. She conceded that it was an intriguing, and highly testable hypothesis, unlike some people who have labeled it as vague. Unfortunately, there has been no continuation of communication between us, although it is now a matter of public record that I am the first to propose this theory. As for the USGS publication that your link suggested as proof that the stones are being blown uphill, that paper cites no scientific data to support it. I should accept is as absolute fact however, because I would HATE to think the US government could ever be wrong in anything. 

Kiteman,  not to stick my nose where it wasn't invited, but in the picture at the site, it appears to me (and I may be wrong in this) that the "path" the rock is making is deeper then the one posted above, leaving what appears to be a shallow gorge, with what seems to be a somewhat powdered wake.  Wind, if this wake is not "wet", would disperse this, I would think.
If it were merely damp, one would think it would (further back) dry up some and blow away.  Neither of these seem to be happening.....not that I am espousing any other hypothesis's put forward,  I am just wondering about the wind thing...

Link?  Preferably to a peer-reviewed research article supporting your contention.  Otherwise, you're making exactly the same kind of unsubstantiated guess as everyone else.

Replying to 18-month past posts as though they should have already seen what you've only posted today is not entirely good manners.

it's alive!!!! jk

this will sound slightly stupid but what if they're is some extremely powerful magnetic element that shifts around and these are pulled by it we don't know completely what the core is so it is a venture

You may wish to read through the existing comments below. The correct answer (from the United States Geological Survey) was posted on 14 July 2008.

The USGS site does not express the opinion that the hypothesis proposed is the correct answer. It is just the most popular hypothesis, despite the fact that it is not the answer.

You are referring to statements like this I am guessing? 

may contribute to lower friction coefficients over the long-term in this region.

Wind. Downhill slope. Maybe that's it?

"Racetrack playa is lake bed that is almost perfectly flat and almost always dry"
doubt that its downhill, ;)

It's downhill when the rocks slide. The surface is dynamic, not static. See the post about frost heave.

Lol, I missed that. I have no clue then.

Brian Dunning of the Skeptoid podcast had an interesting show about this: http://skeptoid.com/episodes/4021 . It's well worth a listen, and you can see the phenomenon captured on video.

Brian Dunnings video DID NOT show the rocks moving. He witnessed water moving, and inferred it to be the cause.

Who says the rocks are moving?

The article says that nobody has seen them move. Has nobody thought of actually checking? It would be very simple: select a rock and mark it in some way, say a splash of paint.

Use a GPS unit to obtain an accurate position and orientation, then come back and check it on a regular basis.

Or set up a webcam to watch it.

If there is a possibility of animals moving it, use a telephoto lens and IR trip-wires to check.

My personal theory, though, is people - look at the random track-patterns in this image - there are sharp kinks and corners with piled-up dirt which would not easily be explained by water, wind or ice-flows, but would be easily explained by a couple of blokes wrapping cargo straps around the rocks to spread the load and dragging it wherever they wanted.

Anybody remember Doug and Dave?

So, they reckon wind moved 300kg boulders?


Yes, indeed. The ground is essentially inert: there are occasional flash floods, but not the kind of continously changing humidity, temperature, and precipitation which causes erosion. Consequently, wind can push a given rock a millimeter or two at a time, and the result, integrated over many years, is the kind of trail shown in the photograph.

It's a beautiful metaphor of nature for evolution in action. Something you, of all people, would appreciate!

The surface of the Playa is not inert. It is capable of dynamic changes due to the fact that the soil type of the playa is composed of a soil type highly conducive to frost heave. In reality, the rocks are moving for the same reason that most rocks do. Gravity.

the wind by itself would have a hard time pushing a rock if it is sitting square with a lot of surface contact to the soft ground. But as you know, the ground is uneven and very hard. imagine a rickety chair with uneven legs sliding. Remember "electric football game"? the board vibrated and moved the plastic players across the board. This is the same principle except the rock is rickety and vibrating in the wind. while the hard ground stays still.

The reason for the sharp kinks and corners with piled up mud relates to the frost heave theory. An already sliding stone ran into a surface fracture created by an ice lens upheaval, stopping the stones momentum, and sending it downhill in another direction.

I wouldn't mind doing a crop circle instructable... I called it first!

It's a new, and very slow moving life-form !