A century ago, miners working in California’s Death Valley reported seeing boulders on the desert floor with long trails behind them as if the stones had been pushed across a dry, muddy surface. But despite decades of trying, no one could figure out how they moved.
Death Valley National Park, located in both California and Nevada, is the largest national park in the lower 48 states. It has the distinction of being the hottest and driest national park.
The place where these mysterious boulders move is the Racetrack Playa (dry lake) and is located in the northwest part of the park. Dotted across the playa are hundreds of rocks, some weighing hundreds of pounds, that seem to have been dragged across the ground leaving tracks in the dry mud that can stretch hundreds of yards.
When I visited here in 1978, experts still didn’t know how these rocks moved.
Boulder on the Racetrack, Photo credit: Getty Images
Scientists Solve the Mystery
In 2014, researchers from Scripps Institution of Oceanography finally solved the mystery when they actually observed the stones being moved by thin sheets of ice pushed by wind. They found that moving the rocks requires a rare combination of events. First, the playa fills with water, which must be deep enough to form floating ice sheets during cold winter nights but shallow enough to expose the rocks. The following morning would need to be sunny enough for the ice to begin to melt and break up into large floating panels, which light winds drive across the playa, pushing rocks in front of them and leaving trails in the soft mud below the surface.
The rocks move under light winds of about 10 miles per hour and are pushed by ice less than 0.25 inch thick (but 40 or 50 feet across). They move a few inches per second which can be really difficult to notice without having a stationary object to compare it to.
The researchers also observed rock-less trails formed by grounding ice panels. Park rangers had previously suspected these were the result of naughty tourists stealing the rocks. I enjoyed reading the scientific process that was used to discover this. You may too and can read it here. Mystery Solved: “Sailing Stones” of Death Valley Seen in Action for the First Time | Scripps Institution of Oceanography (ucsd.edu)
Vandalism and Mischief Problem
Leave no trace principals say “Take only pictures Leave only footprints.” Well, PLEASE DON’T leave footprints in the wet mud at the playa. This area only gets around one to two inches of rain per year so any footprints left in the mud will likely be on the playa for years and years. There isn’t enough water to wash away the damage.
In addition to the muddy footprints in the photo above, back in 2016 somebody used the playa as their own personal racecourse. One eyewitness said that the majority of the surface of the dry lake is cracked leaving behind about 10 miles of looping tire tracks. Illegal tire tracks mar Death Valley dry lake famous for mysterious moving rocks | Las Vegas Review-Journal (reviewjournal.com)
How to Visit
The Racetrack is not a spot you can just visit on a whim. Getting here takes advance planning. The only way to get here is via long, rough, rocky roads through a remote landscape. The following paragraph is a warning from the NPS website.
WARNING: The road to the Racetrack is rough, and good tires, 4×4 and high clearance are usually required. Standard vehicles and small SUVs are not recommended, and often get flat tires. Use extreme caution on this road in the summer heat. There is no cell phone coverage in the area. Do not attempt a trip to the Racetrack without a plenty of fuel and water. There is no cell phone service in the area. Be prepared for the possibility of spending the night if your vehicle becomes disabled.
Do your homework. The Earth Trekkers site gives in depth information about how to visit. How to Visit Racetrack Playa in Death Valley National Park – United States – Earth Trekkers The following page gives in-depth information about how to get there and the author’s feeling about possibly returning. He also comments about the vandalism problem. Is Visiting the Racetrack Playa in Death Valley Worth It? (digital-photography-school.com)
A Nearby, More Accessible Moving Rock Playa
Apparently, this phenomenon is not unique to the Racetrack Playa and has been observed on at least eight other dry lakes in southeastern California and western Nevada. The Bonnie Claire playa east of Scotty’s Castle seems to be a smaller, more easily accessible copy of the Racetrack. The south shore of the playa runs right along the north side of Highway 72. The area is administered by the Bureau of Land Management. This website gives a bit more information on how to get there. Along the Way – Park to Park in the Dark I need to plan a trip back to Death Valley to see how this checks out.
Sources
The Racetrack – Death Valley National Park (U.S. National Park Service) (nps.gov)
Mystery Solved: “Sailing Stones” of Death Valley Seen in Action for the First Time | Scripps Institution of Oceanography (ucsd.edu)
An Icy Solution To The Mystery Of The Slithering Stones : NPR