Mystery of the Racetrack Playa's sailing stones
The Racetrack Playa sits in a remote corner of Death Valley National Park in California, a dry lake bed tucked between the Cottonwood and Panamint mountain ranges. The cracked, flat surface spans roughly 4.5 kilometres long and 2 kilometres wide, and its name comes from a large, oval-shaped rock that resembles a racecourse when viewed from above.
For travellers from Sydney or Melbourne, reaching this corner of the Mojave Desert is a serious commitment. Qantas flights from Sydney to Los Angeles take around 14 hours, then there is a long drive across the California-Nevada border past Las Vegas to reach the park's northern entrance. The journey across the Pacific is part of the appeal for many Australians who plan once-in-a-lifetime trips around the experience, treating the destination the way a grey nomad might plan a Big Lap around the country. The remoteness and the otherworldly scenery feel surprisingly familiar to anyone who has spent time around Lake Eyre or the salt flats of South Australia, where similar cracked surfaces stretch for miles under a hard blue sky.
A lake bed without water
Racetrack Playa is an endorheic basin, meaning water that flows in has no outlet and instead evaporates. During rare desert storms, the surface floods with a thin layer of water just a few centimetres deep, transforming the normally bone-dry mud into a slick, slippery skin. As the water retreats, the clay beneath contracts and forms the geometric mud patterns that give the playa its distinctive appearance.
The rocks scattered across the surface are mostly dolomite, sourced from the surrounding slopes of the Cottonwood Mountains. They range from pebbles to boulders weighing several hundred kilograms, yet somehow they slide across the flat ground, leaving long furrows in their wake.
A long-standing mystery
The phenomenon has been reported since the early 1900s, with prospectors and park visitors noting fresh tracks that seemed to materialise overnight, as if some unseen hand had dragged the stones across the lakebed. Early theories blamed strong winds, pranksters, or even magnetic anomalies, but none of these explanations survived closer scrutiny.
Serious scientific interest grew in the 1940s and 1950s, when geologists from the US Geological Survey began mapping the tracks and weighing individual rocks. The mystery deepened in 1968, when a team from the University of California calculated that some of the larger stones would require wind speeds in excess of 300 kilometres per hour to be moved by air alone, a figure simply not recorded at the site. For readers who enjoy the more personal side of travel writing, lifestyle notes for women often covers the human angle of long-distance journeys to remote American deserts.
How the stones move
| Theory | Mechanism | Strengths | Weaknesses |
|---|---|---|---|
| Wind alone | Strong gusts push lightweight rocks | Simple, no special conditions required | Cannot move heavier boulders on slippery mud |
| Wind on floating ice | Thin ice sheets form around rocks, wind pushes the ice raft | Matches the seasonal timing of track appearance | Requires specific overnight temperatures |
| Wind on wet clay | Rocks slide on a thin film of water | Reproduced in small-scale experiments | Harder to apply to very large stones |
| Microbial mats | Slippery biofilm reduces friction | Matches observations in some locations | Limited supporting evidence at Racetrack |
The most widely accepted explanation combines several of these factors. Researchers tracking stones with GPS between 2011 and 2013 found that movement was associated with particular weather patterns: a brief thaw after freezing nights, when the ground was wet and the sun was just warm enough to soften the ice. As the thin ice panels began to melt and break apart, light winds of around 8 to 16 kilometres per hour were enough to push the rocks, sometimes for just a few seconds at a time.
Reading the tracks
The trails left behind tell their own story. Some tracks run in almost perfectly straight lines for hundreds of metres, while others curve gently, double back, or change direction abruptly. A few stones have been observed to travel in parallel, suggesting they were embedded in the same moving sheet of ice.
For geologists visiting from the Australian outback, the patterns are reminiscent of features found in the Strzelecki or Simpson deserts, where wind-shaped surfaces produce similarly striking textures. The Racetrack's signatures are simply more pronounced because the surface is so flat and the rocks so hard, a level of clarity that has made the site a regular case study in undergraduate geology courses at universities from Perth to Hobart. Each furrow records a moment when stone, water, ice and wind combined in just the right way, a record that disappears within a few years as wind and rare floods gradually smooth the surface again.
Planning the journey
There is no public transport to Racetrack Playa, and the last stretch requires a high-clearance vehicle along a rough, unpaved road from the town of Ubehebe. Most visitors approach via the Grapevine Canyon Road, which forks off the main park road near Stovepipe Wells. Drivers coming from the south often pair the trip with a stop at the Mesquite Flat sand dunes, the most photographed dunes in the park, and a wander through the golden canyons of Mosaic Canyon.
Australians planning a visit should keep a few practicalities in mind before flying out, and many of the same principles apply to longer road trips across the Nullarbor Plain or out to Uluru, where self-sufficiency matters just as much. A few essentials for the Racetrack:
- The US has separate customs rules from the Australian Border Force, and fresh fruit, raw nuts and untreated outdoor gear must be declared on entry to avoid a hefty fine.
- Summer temperatures at the playa regularly climb above 40°C, similar to Marble Bar or Alice Springs at their hottest, so carry more water than you think you need.
- The nearest fuel and supplies are at Stovepipe Wells, and the road can close after heavy rain, so check park conditions before setting out.
- Cellphone coverage is patchy, and a satellite messenger is a sensible investment for anyone used to the communication blackspots of the Kimberley or the Pilbara.
Readers piecing together a wider US itinerary can browse the site's homepage for other unusual stops worth adding to a California road trip.
Other sliding stones and sounding sands
The Racetrack is not the only place on Earth where stones seem to glide on their own. Smaller examples have been recorded in several other dry lake beds around the world, including the Little Bonnie Claire Playa in Nevada and the Salar de Uyuni in Bolivia. On a separate but equally strange note, the singing sand dunes of Altyn-Emel in Kazakhstan produce a low, humming note when sand cascades down the slopes, a phenomenon that owes its existence to particular grain sizes and humidity.
A few other places worth comparing for travellers who enjoy the offbeat side of geology:
- Little Bonnie Claire Playa in Nevada, where lighter rocks leave shorter tracks.
- Salar de Uyuni in Bolivia, famous for its mirror-like wet season and occasional sliding stones.
- Altyn-Emel National Park in Kazakhstan, home to the booming Singing Dune.
- Margins of Lake Eyre in South Australia, where rare flood events sometimes shift small stones in the mud.
From the cracked floor of Death Valley to the salt lakes of Bolivia and the booming dunes of Central Asia, the planet still holds plenty of puzzles that science has only recently begun to untangle, and the next breakthrough may well come from a researcher who grew up staring at similar features in the Australian outback.