Movin' On

They're called moving rocks or, sometimes, sliding rocks, or even sailing stones, and they move, slide or sail across the dry lake floor of Racetrack Playa in California's Death Valley National Park. But while we know what they do, we don't know how. Though the trail of evidence is unmistakable and undeniable, no one's ever actually seen them move. The prevailing theory is that their slow, intermittent progress takes place when winter winds of up to 90 miles an hour combine with seasonal snow melt and cold night temperatures to push, and sometimes tumble, the rocks along the slick surface of the clay bed. But no one knows for sure.

What we do know is that while it looks like this rock skidded to a stop in front of Peter Hemming, it didn't.

Pete, who can best be described as an adventure photojournalist, came to Death Valley about a year ago to see and photograph the stones. He camped out and woke early to take advantage of the great light and the long, strong shadows of sunrise.

Setting his tripod low to capture this softball-size rock, he zoomed his 17-35mm lens back "to include the trail the rock had left and the desolate region." The morning light served "to give the rock depth and accent the pattern of the dry broken ground of the lake bed."

He made the picture with a D300 and an AF-S Zoom-NIKKOR 17-35mm f/2.8D IF-ED. The settings were 1/100 second, f/14, ISO 200, and he used manual exposure and spot metering. He also used a two-stop graduated neutral density filter to hold back the light a bit.

Pete says that he saw several rocks of the same size in the immediate area—some with similar trails, some that had apparently taken zigzag paths to their (perhaps temporary) destinations.