Skip to comments.Astronomy Picture of the Day -- A Sailing Stone in Death Valley
Posted on 02/21/2012 9:54:30 PM PST by SunkenCiv
Explanation: How did this big rock end up on this strange terrain? One of the more unusual places here on Earth occurs inside Death Valley, California, USA. There a dried lakebed named Racetrack Playa exists that is almost perfectly flat, with the odd exception of some very large stones, one of which is pictured above. Now the flatness and texture of large playa like Racetrack are fascinating but not scientifically puzzling -- they are caused by mud flowing, drying, and cracking after a heavy rain. Only recently, however, has a viable scientific hypothesis been given to explain how 300-kilogram sailing stones ended up near the middle of such a large flat surface. Unfortunately, as frequently happens in science, a seemingly surreal problem ends up having a relatively mundane solution. It turns out that high winds after a rain can push even heavy rocks across a temporarily slick lakebed.
(Excerpt) Read more at 18.104.22.168 ...
[Credit: Nathan Alexander, Wikipedia]
And what does this have to do with Astronomy? I enjoy the “Astronomy Picture of the Day” greatly, however ...
Did you know that Death Valley is sinking? The valley has been sinking about 1/2 in per year.In relation to the valley, the Black Mountains under you are movng to your left as well as rising. The eroding mountains fill the valley at about the same rate as it sinks.
Don't have an answer, but I'm not buying that wind pushed a 660 pound rock.
Death Valley is mentioned in several prominent Astronomy Books. In fact NASA tested the Viking probes to Mars here.
Still, what does this have to do with our daily Astronomy picture of the day. This should be presented in “Our Geology Picture of The Day”, not here.
NASA has also Death Valley on their Earth Observatory site,too
Death Valley has similar geology to the Red Planet
So, in my repartee of saved Astronomical pictures, I should consider this one as just another “astronomical phenomenon”?
Death Valley is a important site on the planet and in Solar System.
You do realize that it is “wind” that lifts a Boing 747-400 weighing 870,000 lbs (max takeoff wt) up into the air.
SO on an extremely “slick” (very low coefficient of friction) muddy surface, a very strong desert wind - which can easily exceed 100 mph - can generate enough horizontal force to break the rock free, and then, once it is moving, slide it these long distances.
Visualize a weatherman showing off in a hurricane, and being blown away down the road.
Weatherman - rock - basically the same thing... :-)
:-) to any weathermen, don’t be offended.
Not sold. BTW, a 747 has wings.
Morelocks. That’s my guess.
“Don’t have an answer, but I’m not buying that wind pushed a 660 pound rock.”
Think of a beer being slid from on end of a bar to the other.
I’ve read about this for years. I first came across it in a strange phenomenon book from the 60s or early 70s and this was given as one particularly plausible explanation. Its really neat, but nothing new regarding science.
You obviously do not understand Science.
What makes this different than all those decades old speculations is that this is prefaced by, "Scientist says...".
But a truck or a van doesn't, and the wind can push on those hard enough to tip then over or push them off the road.
Sounds like a job for Myth Busters. Although the photograph in question with the trail in the dirt running up to the rock, and no vehicle tracks, footprints, etc. would also seem to support the theory. Or maybe leave a cheap webcam triggered by motion on a tripod (VERY WELL ANCHORED!) by the rock and wait for the next windstorm might confirm it.
Actually wind doesn't lift the airplane, vacuum does. The air going over the top of the wing moves slower than the air going under it and creates a vacuum, the air rushing to fill the vacuum lifts the plane. This is a different, and quite a lot stronger, force than simple wind. There is no vacuum created in front of the large rocks that move, at least I don't think so, unless the rocks have an airfoil shape to them.
You mean it’s NOT Giant Aliens playing checkers?
I am SO disappointed! :-)
Despite the extensive work conducted most notably by Kirk (1952), Stanley (1955), Sharp and Carey (1976) and by Reid et al. (1995) the causative conditions promoting the sliding rocks motions remain unclear.
At the outset this project was conceived and designed in hopes of revealing predictable order in the sliding rock trails. The patterns have been successfully captured for the first time to high accuracy standards, and they do indeed show general trends. Yet the degree of chaotic motion implied by the furrows, and the insignificant correlations of rock and trail parameters, are remarkable. Perhaps the most surprising outcome of this research is the unanticipated lack of order in this natural system. Countless efforts to establish statistically significant relationships between rocks, trails and terrain characteristics yielded disappointing results.
I’ll take glacial deposit for $100 dollars Alex. heh
That’s generally how things got moved around into the strange positions we see them today, although this does look odd even for that.
Ice shanties on snow free ice need to be anchored or they will be blown away on high wind days.....
I've had to chase down ice buckets that were blowing away while I was drilling holes for icefishing.
It’s the flying rocks you have to watch out for.
If the ground turns to mud, it never rains enough to wipe out the track behind? Or rains but the wind isn’t strong enough to break the rock free? I can’t see by the pick if there is any water erosion on the trail of the rock, doesn’t look like any to me.
Seems like you would only get that type of thing if every time it rained the rock only moved after the rain stopped. But why wouldn’t the next rain wipe out the track behind? Maybe the rain only moistens the very top level of soil? But then you would think there would be a lot more friction, that looks like a fairly deep furrow. The furrow itself looks like the rock almost scooted along on three points, with places between where the mud is cracked from the heat like the rest of the ground.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.