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Archive 2011 · How Do Rocks Race?

  
 
Mike K
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p.1 #1 · p.1 #1 · How Do Rocks Race?


While visiting Death Valley's Racetrack, I met Gunther Kletetschka, a research professor, studying how the rocks at the racetrack move and create the playa mud trails we are so fond of.
http://www.fototime.com/67DFC432E1CFF29/orig.jpg

This question as to the mechanism of the rock trails is one that has captured people's imagination for some time. No one has ever actually seen the rocks move, as it is likely to be under the most uncomfortable conditions. Proposals I had heard in the past involved the wet playa being frozen, or mostly frozen, and very strong winds driving the rocks across the playa, leaving tracks.

Prof. Kletetschka's hypothesis is that the playa floods with an inch or two of water in a rare Winter storm, then freezes from above as the air temperature plunges at night. A sheet of ice forms around the rocks and encases their base forming an ice collar. More water flows into the playa via known springs or additional runoff, and the ice sheet floats the rocks a fraction of an inch above the playa clay mud. A strong wind, measured up to 100 mph, drives the partial ice sheet across the playa taking the rocks with them. The wind is blowing the ice sheets with the embedded rocks, not the rocks slipping on the ice as had previously been proposed.

It has been shown that with extremely high winds most rocks will tumble across the frozen playa, not slide. At times, these ice sheets could be fairly large in area and have substantial mass, thus having the force to move larger rocks and create larger trails.
http://www.fototime.com/60836F09DB465FF/orig.jpg

This theory of floating ice sheets taking the rocks, also explains why small and large rocks can move as one, with parallel tracks. If the rocks were simply blown over the frozen playa, the small rocks would move much faster or tumble producing different shaped tracks.
http://www.fototime.com/B9506C8C4634E01/orig.jpg

If more water floods the playa the rocks will be lifted free of the playa clay mud and the ice movement will result in the rock being carried away without leaving a trail. This also explains why more than 1/2 of all the Racetrack rock trails have no rock at either terminus. I originally thought that vandals carried the smaller rocks home, but this proposal is far more sensible.
Of course the wind can change direction and velocity, making for curves in the tracks, or different storm events can lift and move some rocks and not other nearby rocks. This results in tracks going in very different directions, but these tracks could be created in different events and possibly years apart.
http://www.fototime.com/FD4F5C26322E41D/standard.jpg
http://www.fototime.com/FB5A6531786F2E8/standard.jpg
http://www.fototime.com/0EB2C9FB66B8C05/standard.jpg

The idea that the floating ice sheets carry the weight of the rocks is much more plausible as the largest rocks are very heavy, estimated to be several hundred to 700 pounds as they are easily several cubic feet of solid rock.
http://www.fototime.com/B09076924AFC098/orig.jpg

Of course Prof. Kletetschka has a good deal of data to back up his hypothesis; I just summarize his proposal here as a context for sharing some of my racetrack photos.
http://www.nasa.gov/topics/earth/features/roving-rocks.html

When taking these photos I wondered why the polygon pattern is so uniform in size, approximately 3" in diameter. Kletetschka explained that the playa is a mixture of clay and silt, and when the clay dries it shrinks creating the cracks in the surface. The surface of the playa is very uniform in composition and thus the cracks, patterns in the playa, are also very uniform in frequency.
Sorry for running over the image count: I was hoping this would be considered "an exception" as it seemed to be the best forum for this subject.
Mike K


Edited on May 02, 2011 at 04:56 PM · View previous versions



May 02, 2011 at 11:56 AM
David Leask
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p.1 #2 · p.1 #2 · How Do Rocks Race?


Interesting and plausible theory Mike.
Fabulous shots!
Thanks for sharing both.
David



May 02, 2011 at 12:11 PM
gdanmitchell
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p.1 #3 · p.1 #3 · How Do Rocks Race?


That flooding/ice/wind hypotheses has been around for a while and seems like the most reasonable one. (Unless you believe in little green men... ) Some used to think that water and wind alone were enough, but someone calculated that the wind velocities required to move the largest rocks that way would be far greater than anything that is plausible.

I'm to completely convinced by the "rocks frozen in water that rises enough to move them without tracks" idea. First, that would be a quite astonishing amount of added water when you consider the vast expanse of the playa... and it would have to occur with astonishingly unlikely coincidence with the freezing and the wind.

I would most certainly not dismiss the vandalism idea. Sadly, and somewhat astonishingly, there seems to be some real evidence of that.

Dan



May 02, 2011 at 01:24 PM
Mike K
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p.1 #4 · p.1 #4 · How Do Rocks Race?


gdanmitchell wrote:
That flooding/ice/wind hypotheses has been around for a while and seems like the most reasonable one. (Unless you believe in little green men... ) Some used to think that water and wind alone were enough, but someone calculated that the wind velocities required to move the largest rocks that way would be far greater than anything that is plausible.

I'm to completely convinced by the "rocks frozen in water that rises enough to move them without tracks" idea. First, that would be a quite astonishing amount of added water when you consider the vast expanse of the playa... and it would
...Show more

Dan, the difference in this hypothesis is that an ice collar/sheet supports most of the weight of the rock via flotation. This differs from rocks being individually blown over a frozen playa ice sheet.
I am told that well before DV was a park, that someone landed a plane on the frozen playa to generate 100+ mph winds to test the wind/sliding on ice theory. The rocks did not slide, they tumbled. In particular this makes sense with the smaller rocks.
There are several known springs in the playa, as one source of additional water. Obviously additional run off can occur from the numerous washes around the playa as well. The amount of additional water does not have to be much, just a fraction of an inch in the right areas. I think many of the rocks are too large to carry away. Graduate students (the academic version of slave labor) counted all of the tracks with no rocks, over half! check out the reference link.
Mike K



May 02, 2011 at 02:37 PM
alichty
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p.1 #5 · p.1 #5 · How Do Rocks Race?


This is a fun read - thanks Mike. I do like Dan's little green men theory the best but that isn't likely to get much traction with the research crowd

Thanks for the reference link - research projects like these are always easier with a nice supply of grad students to do the data collection (graduate school: It's not just a job - it's an indenture).....

Alan



May 02, 2011 at 03:03 PM
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p.1 #6 · p.1 #6 · How Do Rocks Race?


excellent read Mike, thanks for sharing both the thoughts of the professor and your images whch really bring it to life for use foreigners

simon



May 02, 2011 at 03:10 PM
Rosemary R
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p.1 #7 · p.1 #7 · How Do Rocks Race?


It's a fascinating subject and I like this theory. Nice photos, too.



May 02, 2011 at 04:42 PM
Aaron Cowan
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p.1 #8 · p.1 #8 · How Do Rocks Race?


Great info. I like the hypothesis. However they move, they keep us photogs going back!


May 02, 2011 at 10:55 PM
Bandi
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p.1 #9 · p.1 #9 · How Do Rocks Race?


Fascinating stuff Mike and thanks for compiling it. Great set of images to go with it too!

Anthony



May 03, 2011 at 05:53 AM
bshamilton
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p.1 #10 · p.1 #10 · How Do Rocks Race?


Cool stuff. Dig the u-turn in the next to last.

Barry



May 03, 2011 at 06:21 AM
JimFox
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p.1 #11 · p.1 #11 · How Do Rocks Race?


Hey Mike,

A very interesting read here. And while it can be inhospitable out there in the winter time, it's still amazing that it's still such a mystery... I had heard at one time that web cams were going to be set up to monitor the rocks, that would seem to be pretty feasible.

As to the missing the rocks on the trails... I caught 2 people taking a rock off the Racetrack one of the times that I was there. There are people who take the mystery as some kind of magic... and they think by taking the rock they can take that magic with them it seems... Perhaps solving this mystery would help reduce the # of rocks taken?

Whether this professor is correct or not, some things he says make sense, but then a few things didn't totally make sense either... But still, an interesting read, and it must have been a fascinating time for you to talk with him.

Jim



May 03, 2011 at 07:16 AM
gdanmitchell
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p.1 #12 · p.1 #12 · How Do Rocks Race?


Mike K wrote:
No, that actually is a very plausible theory that I first heard several years back. I've posted a few times repeating it here and elsewhere.
Dan, the difference in this hypothesis is that an ice collar/sheet supports most of the weight of the rock via flotation. This differs from rocks being individually blown over a frozen playa ice sheet.
I am told that well before DV was a park, that someone landed a plane on the frozen playa to generate 100+ mph winds to test the wind/sliding on ice theory. The rocks did not slide, they tumbled. In particular
...Show more

I've done a fair amount of reading on this subject, and I wouldn't dismiss the possibility of some rocks moving without tracks... any more than I would dismiss the likelihood of some moving without tracks... to the vehicles of thoughtless morons who now have a dumb rock on their mantels. :-)

It is interesting to read about the various research projects and the ideas that they have given rise to. One project a few years back was using GPS to map the locations of virtually all of the rocks on the playa. (The researchers ended up also assigning female names to many of the rocks. If you have shot out there enough, some of the individual rocks do start to feel a bit like old friends! I saw a TV program on the playa last night and drove my wife crazy by repeatedly exclaiming, "I know that rock! And that one, too!")

One earlier thing I read debunked the idea that wind alone could move rocks on a playa that was just wet. The idea had been that that playa mud would be so slippery that wind would cause the rocks to slide on top of the lubricating mud. I don't recall the exact details, but someone did some calculations based on the size and mass of the largest rocks and determined that, yes, wind could move rocks across a silt-covered playa... but that it would be something like an 800 mph wind! (I've been out there when it was very windy, as it often is, but I'm not buying the 800 mph wind potential! :-)

Another account that I read suggested that more than one process might be at work. In this case the researcher(s) suggested that some of the smaller rocks could, indeed, be moved simply by the action of wind and be propelled across the playa without the need for ice, but that others might require the ice.

The other thing that still seems to be unresolved is how frequently the rocks move. I'm no geologist, so I certainly cannot claim any real expertise on this stuff. However, when I first heard about the Racetrack and the moving rocks I think I fantasized about the vision of rocks regularly sliding across the playa in heavy winds. Then I visited and began to imagine that such a thing might happen, oh, may be every decade or so. After more visits and more poking around and some reading and thinking, it occurred to me that the interval between conditions that would be ideal for moving rocks might be very long indeed. I'm guessing that it might be at least decades and perhaps even centuries.

In any case, it is a marvelous and thought-provoking place.

Take care,

Dan



May 03, 2011 at 09:29 AM
tazmans
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p.1 #13 · p.1 #13 · How Do Rocks Race?


I find this to be a very believable hypothesis. As water freezes it expands and this would account for the "lift" of any item. As seen with glacier's, the scoring on the smooth faces of cliffs and shelves of the same process, large embedded rocks of incredible size and weight flowing along with the ice and scouring the surface. I'll buy in on the theory. Great shots by the way. Ron


May 03, 2011 at 09:46 AM
kwalsh
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p.1 #14 · p.1 #14 · How Do Rocks Race?


So there was one test a number of years ago that established that certainly some rocks can move without an ice collar. Researchers surrounded some rocks with stakes spaced far enough that the rock could "get out" on its own, but if in an ice sheet the stakes would hold the sheet and there would be no movement. Indeed, a few rocks departed from their stake "cages" leaving trails. I heard this from both Robert Sharp and Arden Albee (Caltech geologists) but I don't recall who did the study (definitely not Albee, but I'm not sure it was Sharp or another geologist).

Regardless, I think there is a fair bit of consensus that ice is likely involved in some/most movements even if it isn't strictly necessary.

Ken



May 03, 2011 at 09:52 AM
Mike K
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p.1 #15 · p.1 #15 · How Do Rocks Race?


JimFox wrote:
Hey Mike, I had heard at one time that web cams were going to be set up to monitor the rocks, that would seem to be pretty feasible.

As to the missing the rocks on the trails... I caught 2 people taking a rock off the Racetrack one of the times that I was there. There are people who take the mystery as some kind of magic... and they think by taking the rock they can take that magic with them it seems... Perhaps solving this mystery would help reduce the # of rocks taken?
Jim


Jim,
My understanding is that video monitors have always been blown down, so its still a mystery.
I appreciate your first hand knowledge of vandalism of the site. I kind of expect it, given what some folks do.

Mike K



May 03, 2011 at 12:13 PM
Sunny Sra
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p.1 #16 · p.1 #16 · How Do Rocks Race?


Very cool info and shots to go with it. Thanks for sharing these and the link to the research.


May 03, 2011 at 12:23 PM
ioana o
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p.1 #17 · p.1 #17 · How Do Rocks Race?


as a geologist, i find this very interesting. thanks for the posting.

Edited on May 03, 2011 at 12:39 PM · View previous versions



May 03, 2011 at 12:29 PM
Mike K
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p.1 #18 · p.1 #18 · How Do Rocks Race?


gdanmitchell wrote:
It is interesting to read about the various research projects and the ideas that they have given rise to. One project a few years back was using GPS to map the locations of virtually all of the rocks on the playa. (The researchers ended up also assigning female names to many of the rocks. If you have shot out there enough, some of the individual rocks do start to feel a bit like old friends! I saw a TV program on the playa last night and drove my wife crazy by repeatedly exclaiming, "I know that rock! And that one,
...Show more

Dan,
http://geology.com/nasa/racetrack-playa/
This article, although written from the NASA one I referenced in the original post, gives a few additional details. This team is mapping the movements of the rocks with GPS, and I saw Kletetschka doing just that. What progrm is that you saw on TV? While I was out there several videographers took a few seconds filming of my shooting rocks and said I might be on TV.
Agreed that the rocks don't necessarily move every season. That is why some rocks seem to be moving in different directions, they were moving in totally different storm events. Also the track and mud birm many of the rocks create, show weathering, suggesting they have been there several seasons or several storm events.
Mike K




May 03, 2011 at 12:36 PM
gdanmitchell
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p.1 #19 · p.1 #19 · How Do Rocks Race?


Mike K wrote:
Dan,
http://geology.com/nasa/racetrack-playa/
This article, although written from the NASA one I referenced in the original post, gives a few additional details. This team is mapping the movements of the rocks with GPS, and I saw Kletetschka doing just that. What progrm is that you saw on TV? While I was out there several videographers took a few seconds filming of my shooting rocks and said I might be on TV.
Agreed that the rocks don't necessarily move every season. That is why some rocks seem to be moving in different directions, they were moving in totally different storm events. Also the track
...Show more

There was an episode of "Eye on the Bay" on CBS TV in the San Francisco Bay Area last night, on which they visited Death Valley. One of their three reporters (Brian somebody) made it out the Racetrack - looked like he drove out during the day and back after dark - and they did show some brief shots of perhaps two different photographers shooting the place.

This URL is related to their program: http://sanfrancisco.cbslocal.com/2011/05/02/eye-on-the-bay-desert-roadtrippers-pt-1-5211/

Dan



May 03, 2011 at 01:02 PM
Mike K
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p.1 #20 · p.1 #20 · How Do Rocks Race?


Thanks for the link Dan,!
I too remember most of the rocks they feature in the show (last clip). The video team showed up late in the afternoon and filmed for less than an hour. They got some decent footage for such a spontaneous interview.
Mike K



May 03, 2011 at 02:26 PM
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