Astronomy Picture of the Day -- A Sailing Stone in Death Valley

NASA ^ | February 22, 2012 | (see photo credit)

[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.

[21twelve]

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.

[calex59]

You do realize that it is “wind” that lifts a Boing 747-400 weighing 870,000 lbs (max takeoff wt) up into the air.

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.

[left that other site]

You mean it’s NOT Giant Aliens playing checkers?

I am SO disappointed! :-)

[aruanan]

It turns out that high winds after a rain can push even heavy rocks across a temporarily slick lakebed.

Once they're moving, but what gets them unstuck to begin with?

[aruanan]

From the Conclusion in the dissertation (emphasis added):

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.

[Bulwyf]

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.

[aruanan]

"Don't have an answer, but I'm not buying that wind pushed a 660 pound rock."

See post 25. It's funny how NASA refers to a dissertation that flatly denies the claim made in the sentence referring to it.

[Hot Tabasco]

Visualize a weatherman showing off in a hurricane, and being blown away down the road.

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.

[Blogatron]

It’s the flying rocks you have to watch out for.

[TheOldLady]

God gives us these puzzles to solve. This one is a toughy.

Death Valley taught me one thing. Even water that is hot from sitting in the car tastes very, very good after you've been hiking in 110-degree heat.

It is a beautiful and terrific (in the original sense) place.

[Ransomed]

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.

Freegards

[SunkenCiv]

Thanks!

[SunkenCiv]

/bingo.