It’s December 2013, and scientists Jim and Richard Norris are at Racetrack Playa in California’s Death Valley National Park. There to check on an experiment that they are conducting, they suddenly hear crackling noises. And with that, Richard exclaims to his cousin, “This is it!”
But the Norrises weren’t in danger. They were at the playa to study rocks – more specifically, the phenomenon known as sliding rocks. That’s right: not only do some stones move, but they seemingly do so entirely on their own in unpredictable ways. And until the intrepid Norris cousins arrived in California, no one had ever actually seen this happen.
Rocks seemingly sliding by themselves isn’t anything new, though. Indeed, sailing stones appear to exist in a handful of places on the planet. But while there had been theories as to why the rocks at Racetrack Playa moved, there had been precious little scientific confirmation of any of these hypotheses. The Norrises, then, had decided to head to California to try to solve the puzzle for good.
Of course, Mother Nature has been blowing the minds of the general population for centuries. This state of confusion is sometimes only temporary, though, however, as our ever greater understanding of the biology, physics and chemistry of Earth helps us figure out plausible explanations for even the most unusual phenomena.
Take, for instance, the sudden appearance of a new island off the coast of Japan. Yes, in 2013 an entirely new land mass materialized around 600 miles from Tokyo. Many centuries ago, we may have assumed that this was some kind of reverse Atlantis situation; however, these days, we know a little more about how land formation occurs.
This particular island – subsequently named Niijima – was in fact birthed during the eruption of an undersea volcano. Initially out on its own, the little islet has now joined with the larger land mass of Nishinoshima. And in 2013 National Geographic claimed that Niijima may be around to stay for a while. The magazine explained, “Japanese scientists now say that they expect the island has grown large enough to survive for at least several years – if not permanently.”
Speaking of expanded masses, though, stones exist that also appear to grow. Yes, in the town of Coste?ti, Romania, there are a group of rocks – named trovants – that seemingly get bigger over time after spells of rainfall. As a result, a pebble that is initially just a fraction of an inch in size may ultimately grow to more than 32 feet tall.
Are these growing stones actually alive? No, they’re not, although scientists are still mildly baffled by the phenomenon and don’t yet fully understand how it works. One theory is that calcium in the rainwater reacts with the minerals in the trovants; this process then encourages the sand in the rocks to swell.
So, given that science still has some way to go with growing rocks, will it ever be able to fully explain the sliding boulders of Death Valley National Park? Well, the signs are good: there’s evidence that the stones do actually move, which is at least a start. Pristine tracks have shown the routes that they have taken to their current locations in the sand.
Those trails are incredibly varied, moreover: some are small, while others go on for hundreds of feet. A number of tracks have sharp corners, while, intriguingly, still others have no rocks at either of their ends. Meanwhile, their location – Racetrack Playa – is an almost three-mile-long dry lakebed. And the playa itself is in a rather isolated position – at more than 3,600 feet from sea level and in a drainage basin between two mountain ranges.
Despite its location, though, Racetrack Playa is not completely inaccessible, and so those curious about the rocks have made the journey to see them up close. Over the years, there have also been several theories about what causes the stones to seemingly move – ranging from super-strength winds to the magnetic field of the Earth and even, unusually, algae. But until the Norrises ventured to Racetrack Playa, no researcher had ever actually witnessed any movement for themselves.
So, two years prior to that visit to Death Valley in 2013, the cousins had decided to solve the mystery of the moving stones once and for all. And Jim, an engineer, and Richard, a biologist, had the idea of bringing in their own rocks to see if they too would sail. GPS sensors were therefore attached to the new stones, and these were put in position on the playa in 2011. A weather station was also set up there – ostensibly to chart the nature of any winds at the location.
Now all the Norrises had to do was wait. And it wasn’t until 2013, when the pair were at the site checking on the experiment, that their patience finally paid off. Not only did the stones move, but the two were also there to witness the feat for themselves.
With that, the cousins and their research partner, planetary scientist Ralph Lorenz, had become the first ever recorded observers of the sailing stones phenomenon. What’s more, thanks to their GPS and weather-sensing equipment, they also knew exactly how the rocks were moving and what was causing them to do so. The Norrises and Lorenz had just solved a mystery that had been puzzled over for close to 70 years.
Luckily, though, the team were prepared and were able to film the whole event for posterity. And the incredible footage does indeed show a large rock seemingly gliding around – incredibly slowly, that is. So slowly, in fact, that if the video hadn’t been sped up, you probably wouldn’t even notice anything amiss.
So, what was really causing the rock movement? In the end, the answer is fairly simple: ice. It’s not down to the berg-sized chunks that occasionally sink ships, though; instead, the stones are propelled thanks to sheets of incredibly thin frozen water which are themselves moved around the lakebed by the wind. And the unstoppable force of huge sheets of ice may move the Racetrack Playa rocks for considerable distances.
Indeed, during their experiment, the Norrises’ team were able to measure the total distances traveled by individual rocks, some of which had moved in excess of 200 feet. But what exactly is causing ice to form on a dry lakebed? According to the cousins’ research, several key factors must be in play for the phenomenon to occur.
In particular, when rain falls, just the right amount of precipitation should accumulate in the playa. Next, the surface of the lake has to freeze but, crucially, the ice that results should be of a certain thickness. Then, as the sun begins to warm the valley, the ice must crack and split into large sheets rather than just melt away. And, finally, there has to be wind – enough to move the ice panes around on what’s left of the rainwater.
The Death Valley researchers subsequently published the details of their findings in noted journal PLOS ONE, essentially closing the scientific book on the riddle of the sliding stones of Death Valley. But while there may be those who lament the solving of one of nature’s great mysteries, it seems that Racetrack Playa has yet to give up all of its secrets.
Indeed, while the movement of comparatively small rocks has been more or less explained, no one has yet been able to understand exactly how the largest boulders are moving around. The Norrises’ team didn’t witness the huge stones move, either, suggesting that sheets of thin ice may not be enough to make them budge. So, as it turns out, Mother Nature continues to baffle science – at least for now.