Rocks That Slide Across a Dry Lakebed
This photo shows the tracks left behind rocks that have moved across the dry lake bed known as
"Racetrack Playa" ("playa" is the name for a dry lake bed). The fascinating thing about these
rocks is that no one knows for certain how they move. The location is a dry lake bed in Death Valley
National Park, in California. Some of these rocks weigh more than 100 pounds and have moved, in some
cases, hundreds of feet in paths that are sometimes straight, but other times take sharp bends.
The cause of the movement is still in question, as no one has ever actually seen them move. The
consensus is that when the very infrequent rains fall, the mud of the lake bed becomes very slick, allowing
the rock to be pushed by the winds. This idea is supported by the nature of the trails, which clearly
show the displacement of the soil by the rocks, as would be the case if the mud were wet and soft.
The possibility of human or animal involvement is ruled out by the total lack of footprints along, or within,
the paths behind the rocks. There are some videos of the area, but unfortunately none of them capture the rocks in motion.
A Fascinating Optical Illusion!
This one has to be seen in full size to appreciate it. It is an optical illusion which
creates the impression that portions of the picture are moving, as you scan your eyes across it.
Open the full-size picture by clicking on
this link or the picture at the right.
Notice that as your eyes scan across the picture, the regions outside the central focal point will seem
to be turning in different directions. The picture is absolutely a static image - there is no movement
whatsoever. If you are very careful, you will be able to see that the different circles turn in a
direction such that the blue cylinders are in the lead.