posted on Jun, 9 2004 @ 01:50 PM
Rocks that roll? Racetrack Playa in Death Valley, CA has the distinction of being one of the stranger locations in the US do to the fact that the
rocks canít seem to sit still. It's a game of green light/red light that no one seems to have ever see in action
Racetrack Playa is actually a three-mile long dried up lake. Surrounding the lakebed are fairly rugged mountains, which help to channel the winds at
high speeds through the valley below.
At nearly 300 feet below sea level, Death Valley has the honor of being the lowest, hottest, and driest point in the United States.
These rocks, from pebbles to small boulders, leave a trail imprinted in the dry lakebed surface.
At first thought, one would tend to think that gravity is simply pulling these rocks downhill. But this theory can be quickly ruled out. The playa is
so flat that just two inches of rainwater will cover the entire lakebed on a calm day.
Way back in the 1950's, when the scientists started to study this phenomenon, it was believed that the rocks moved due to the combination of
high-speed winds coupled with a slick, muddy lakebed (only two inches or less of rain is received each year). The mud becomes so slick that it acts
like it is treated with WD-40 lubricant. Couple that with the howling winds and those rocks will just glide across that playa.
One scientist, Dr. Robert P. Sharp, supports this theory. Sharp, a professor of geology at the California Institute of Technology embarked on a
seven-year study of this curious wonder. He tagged the positions of thirty stones and watched them for about one year. He recorded the weather
conditions after each move. To no one's surprise, all but two of them moved in the directions of the prevailing winds. A nine-ounce stone moved 690
feet in one giant slide. Another stone moved 860 feet in a series of moves.
Another geologist, John Reid, has come up with an alternative theory. Reid was out on a field trip with a group of students back in 1991. They arrived
to Racetrack Playa right after melting snows had left about five centimeters of water on the lakebed. The mud formed from this meltwater was downright
slippery - one of his students slid between five and six meters. But when Reid tried to move modest sized rocks (25 kg), they wouldn't budge. From
this he concluded that the wind could not solely move the rocks (yet a 200 pound person easily slides along with no wind?).
Back at his lab at Hampshire College in Amherst, Massachusetts, Reid put forward an alternative theory. He proposes that the meltwaters form a thin
layer of ice at its surface. Of course, this ice freezes to the rock surface. Friction due to the wind blowing over the large surface area of the
frozen water causes both the ice and the rocks to move together.
Other reference source information:
Relocate thread if necessary.
[edit on 9-6-2004 by Jonna]