Tuesday, June 07, 2005

I rock, but I'm no playa


Racetrack Playa is a dried lakebed in Death Valley (California) National Park that is home to mysterious moving stones. The stones range in weight from pebbles all the way up to 700-pound boulders. No one knows for sure what causes them to move. In fact, in over 100 years, no one has ever reported witnessing the rocks in motion. But move they do, leaving a trail of flattened earth behind them.

Back in the early 1900's, the popular explanation was that it had something to do with magnetism. The theory in favor currently is that the phenomenon occurs when the right atmospheric conditions coincide, with rain wetting the lakebed surface and a lot of wind. Apparently the fine clay there becomes extremely slick under these conditions, and the wind just sort of pushes the rocks around.

This explanation doesn't satisfy everyone, though. Similar rocks in the same initial location will vary, with one moving and one staying put, or even going in a different direction. Trails, while generally running in a straight line, will sometimes curve sharply in various directions, loop or even reverse direction.

There are a bunch of websites devoted to this strange phenomenon. Here are but a few.

The Sliding Rocks of the Racetrack Playa. They even went so far as to map the position of the rocks using GPS, and track their motion, direction and distance. Cool!

The US Geological Survey mentions it, but doesn't try too hard to explain anything.

DesertUSA's piece on the Sliding Rocks

Bill and Cori's Excellent Adventures "Death Valley Moving Rocks"

Anomalies-Unlimited also covers it

(via growabrain)

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