Rainbow at the Racetrack. It lasted for about 20 minutes which allowed me to get a lot of photos.

EDIT: This paragraph was written in 2016 for this gallery: For a lot of years it was believed that no one had seen the Racetrack rocks move. That changed in 2013. A paleobiologist named Richard Norris and his cousin noticed the rocks moving in December of 2013. At the time the Racetrack was essentially a pond with three inches of water. The water froze and broke into sheets during the day. The moving sheets moved the rocks at a speed of a few inches per second (2-6 meters per minute). Individual rocks could be seen in motion for anywhere from a few seconds to 16 minutes. Some of the rocks moved 200 feet before stopping. Sometimes it can take years or a decade for the rocks to start moving again.

The following paragraph was originally written in 2007 for a different gallery of mine: There are perhaps several hundred of these rocks with trails on the Racetrack playa. The force that allows movement is still up for speculation but the most obvious culprit would be a combination of water (or more likely thin sheets of ice) and wind. These rocks only seem to move once every few years and after 4 to 8 years their old paths have been replaced by new ones. No one has ever seen these rocks move. I suspect that a lot of the reason why is because the playa would require a wet surface and that same weather condition would make the dirt road to the playa impassable hence no one would be on the scene to see them. Rocks can double back on themselves, do circles and leave zig-zag patterns and travel uphill. I have seen a few interesting scientific papers on the subject floating around on the Internet.