gdanmitchell Offline Upload & Sell: Off
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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 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...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
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