California's Death Valley is probably best known for its soaring temperatures, which are among the hottest recorded on the planet. But another natural phenomenon has puzzled scientists for decades; rocks that appear to slide on their own across a dry lake bed.
A Central Coast man says the mystery is now solved. His research was published Wednesday in the journal PLOS ONE.
Several years ago Jim Norris, a Santa Barbara engineer, recruited some local friends as volunteers and his cousin, UC San Diego scientist Richard Norris, to help with the Slithering Stones project.
"We have no outside funding, it's all been self-funded," said Norris about his group's efforts. "It's recreational science, we've been doing this for fun."
But just because Norris was doing it for fun, doesn't mean he wasn't taking it seriously. His cousin helped submit the paper for PLOS ONE using scientific standards.
The National Park Service has also been working with Norris on the project.
Researchers have long held ideas on what might be driving the stones along the lake bed—or playa—leaving long trails in their wake. But, despite the preponderance of theories, none of the researchers had ever seen the phenomenon take place, until Norris and his team witnessed it this past winter.
Many believed hurricane-force winds were pushing the rocks. Others thought ice formed beneath the boulders, floating them across the playa.
Norris says his observations prove both of those theories wrong. He says his group caught the rocks at just the right time when a mixture of rainfall and snow melt had collected in the usually dry lake bed, and the top layer of that water had frozen into thin ice sheets. Too much water and the rocks would be covered, too little and there wouldn't be enough to create the effect.
The temperatures have to cooperate too, because the water has to freeze, but not completely.
If all of the elements align and there's a light breeze, then you have the winning combination to push the rocks along, according to Norris.
"We had stones out on the playa that had GPS [units] in them and some of those moved this winter, and we have really great velocity records off of those," said Norris. "They were moving at maximum 15 feet per minute, and that's a painfully slow walk, it's like a tenth-of-a-mile-an-hour."
While that is incredibly slow, the movement is significant because researchers suspect there hadn't been any movement by the playa rocks since 2006.
Norris told KCBX the park service will be updating their literature related to the phenomenon.