Sliding Rocks Bemuse Scientists 433
An anonymous reader writes "Scientists can't figure out why these rocks — weighing up to several hundred pounds each — slide across a dry lake bed. The leading theory proposes that wind moves the rocks after a rain when the lake bed consists of soft and very slippery mud.
Answer on page 42 ... (Score:5, Interesting)
Quote: "Research of the Racetrack has continued. In the April 1997 GPS World, Paula Messina, Phil Stoffer and Keith C. Clarke reported a GPS study they conducted of the Racetrack. In ten days of intense field work they mapped every featured of the playa using differential GPS to produce, "the first-ever, complete, georeferenced, submeter-resolution map of the wandering rocks." (Messina, 1997, p. 42)"
http://sophia.smith.edu/~lfletche/deathvalley.html [smith.edu]
But it seems they have no real conclusion too.
What about 'The Force"?
CC.
Begs the question (Score:4, Interesting)
Re:no buildup in front (Score:5, Interesting)
In all those pictures, I don't see any buildup of dust in front of the rocks, though there is plenty on the sides of the paths. Usually, when I push something through the dirt/mud/snow/whatever, I end up with a good buildup in front, too. I wonder where that has gone.
I had to think about this for a second... I think the answer is that if a rock was digging into the mud, you wouldn't have this effect, because of having to shove the mass of the mud. If you look at the pictures, the fronts of a lot of them tend to be sticking up, implying they're "surfing" over the mud.
Re:Mark Newman Poster (Score:1, Interesting)
1) many rocks didn't penetrate to the bottom of the mud pieces, which to me says the mud wasn't totally soggy when the rock was moved. How can the top be so soggy that the rock slides, but the bottom still be hard?
2) One of the rock pictures had rubble next to it that looked like it was created from already dry clay crumbled up.
Just seems to me that instead of crazy rocks sliding round on their own, some damn kids were up there fucking round with rocks.
One possibilty (Score:5, Interesting)
Re:Begs the question (Score:1, Interesting)
If you're trying to see if the movement is due to wind, you set up wind instruments that turn the webcams on when the wind blows hard.
You can also attach some kind of GPS reporting system to a moveable rock that calls home when it begins to move, and turns on the cameras at the same time.
Flowing water can generate more force than wind. I would suggest that the rocks may be more susceptible to being moved when the wind is blowing hard enough to get the water helping to first free the rock, then push against it. I'd guess that a shallow water depth may provide the right conditions - with a very strong wind, water will be able build up behind the rock and sweep it along. A shallow depth could even help create a hydroplane condition.
Problem with the ice or even water theory (Score:4, Interesting)
The cracked effect is what you get when muds dries out, the effect is NOT visible in the trails. How can this be IF the rocks moved when the mud was still there? There is a cracked effect in the trail but it is crushed, the effect you would expect if the rocks had been moved AFTER the ripple effect had already started to form, AFTER the mud started to dry or even when it was already dry.
But if the rocks moved on ice then AFTER the ice melted there would be mud, that if dried would show the same pattern all around the newly positioned rock with just the ridges of the trail left. NOT flattened dried mud.
As for purely the wind moving them, how fast do the winds get there anyway? Wind can be extremely powerfull even in areas with lots of obstructions, in open areas, well if it can pick up/move trucks, why not rocks? Far heavier things are lifted up by air alone, how do you think aircraft work?
Re:Mark Newman Poster (Score:5, Interesting)
The toilet seat lid was covered in a fine layer of condensation from the bath water at the time.
I'm betting if the stones are cooled way down to almost freezing by the wind, or maybe frozen overnight and still cold when the rains hit, and the top surface of the mud turns into a slurry of fine particles, the stone will move around all on its own just like my cold glass of water on a fine layer of condensation.
Either that or space aliens.
Re:Mark Newman Poster (Score:5, Interesting)
Problem is that storms come up rarely but suddenly there (usually) and it takes almost two hours to get to the Racetrack from the nearest paved road - three hours from the Death Valley visitor's center - and if you get out there before a storm, there's no guarantee that even a very capable 4x4 will get you back afterwards.
Ian M. Banks connection? (Score:1, Interesting)
Another theory (Score:3, Interesting)
Perhaps, when the ground is wet, there's a mud layer slightly beneath the surface that becomes fluid. Then, tidal foces make the surface to move up and down creating waves. The waves migh be very low amplitude (a few cm could be enough) and low speed/frequency, but enough to make the rocks slowly slide on the dry (or slightly moist) surface.
Does it sound plausible?
Re:Mark Newman Poster (Score:1, Interesting)