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Sailing Stones Explained: Why & How Do They Move? (7 Facts)

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Can you imagine 300 kg of rock moving in a desert and leaving tracks behind without any help? Sounds ridiculous.  But it has a rational explanation. What has come to your mind? Stormwind? Magnetic field? Today we would like to unravel this natural phenomenon for our readers. 

Sailing stones are stones that move in the desert and leave a track on a mud button behind. Their movement is explained by thin ice rafts, with the stones frozen into them. A slight wind is enough to move the ice platform and rock, which slide on the slippery mud bottom.

Sailing stones of the Death Valley have puzzled scientists for about a century. A bunch of theories have been suggested, including an extraterrestrial one. Only in 2014, the explanation was found.

To explain the natural phenomenon, a combination of very specific conditions is needed: heavy rains, mud surface, cold nights, ice, a warm sunny day, and slight wind. How does it work? It’s an honor for us to guide you.

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What Are Sailing Stones and Why do Sailing Stones Move?
What Are Sailing Stones and Why do Sailing Stones Move?

What Are Sailing Stones? Scientific Explanation

After several decades of study and observation, the sailing stones of Racetrack Playa have been observed in motion!  In December 2013, paleobiologist Richard Norris and his co-author and cousin Jim Norris reported first-hand observations of the phenomenon.

Sailing stones, or moving rocks, are any composition stones that move on the flat mud surface and leave a trail behind them. Their movement is caused by thin ice sheets the stones are frozen into. Sailing stones move due to ice rafts created in winter after the heavy rains.

Researchers documented multiple rock movement and trail formation events by in situ observation, video, time lapse cameras, a dedicated meteorological station, and GPS tracking of instrumented rocks.

They reported dozens of rocks with simultaneous movement, fresh trails of 10s of meters in length, and speeds of 2 – 6m per minute. The movement was clearly caused by wind stress on a transient thin layer of floating ice.

What Are Sailing Stones in Death Valley

The Death Valley, California, USA  – is one of the most unusual places on Earth. There is a dried lakebed named Racetrack Playa. It is almost perfectly flat, with the odd exception of some very large stones. And these stones move!

Sailing stones of the Racetrack Playa in Death Valley National Park, California, USA – are the best-known sailing rocks in the world. They are boulders that leave a trail on the mud surface of a dried lakebed behind. Multiple stones show parallel tracks, including synchronous high angle turns.

The Racetrack Playa is a 4.5 km x 2 km lakebed at an elevation of 1130 m, which is only occasionally flooded. It is exceptionally flat.

The south end is only a few centimeters lower in elevation than the north and composed of mixed sand-silt clay, usually with striking but small desiccation polygons.

It is distinguished by the unusual presence of some dozens of rocks, usually cobbles or small boulders, which are very distinct against the very uniform playa.

The stones often appear at the end of trails or furrows on the playa surface. These trails suggest that the rocks have moved across the surface when the playa was wet.

Remarkably, multiple rocks commonly show parallel tracks, including apparently synchronous high-angle turns and sometimes reversals in travel direction.

How Was the Sailing Stones Formed

The sailing stones don’t require any specific formation conditions. Sailing stones are usually stones with dolomite and granite composition. Sailing stones require a specific environment, where they can move.

There is nothing special about the sailing stone formation. They are ordinary rocks that were accidentally placed into specific conditions. Sailing rocks are mostly composed of dolomites and granites, which were previously a part of local surrounding cliffs and outcrops.

TIP: Sailing stones are founded in the Death Valley, California. Earthquakes are very common in this area. Find out what rocks are often founded in these areas in the article below:


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Why do Sailing Stones Move

The puzzle of sailing stones remained unresolved until winter 2013-2014 when after several decades of study and observation, the sailing stones of Racetrack Playa were observed in motion. Scientists were able to document the environment and the factors which create movements.

Sailing stones move only when they are frozen into thin ice sheets. Wind pushes ice platforms and frozen rocks into them. Another important factor is the slippery mud surface of the bottom, which lets the rocks slide. That’s why heavy rains are required in winter to create all the necessary conditions.

During winter 2013-2014, a group of scientists was present while the playa was flooded and frozen.

A steady wind drag moved the thin ice sheets covering the playa’s south end, and these sheets pushed the rocks along, creating the characteristic furrows in the playa’s muddy surface.

The movement observed involved dozens of rocks, forming fresh trails typically of 10s of meters in length at speeds of ∼ 5 cm s−1 and were caused by wind stress on a transient thin layer of floating ice.

Their observations show that moving the rocks requires a rare combination of events:

  • Water. The surface should be flooded. Water, which must be deep enough to form floating ice during cold winter nights but shallow enough to expose the rocks. 
  • Temperature. As nighttime temperatures plummet, the pond freezes to form thin sheets of “windowpane” ice, which must be thin enough to move freely but thick enough to maintain strength. 
  • Sunny days. On sunny days, the ice begins to melt and break up into large floating panels.
  • Wind. Light winds drive ice sheets across the playa, pushing rocks in front of them and leaving trails in the soft mud below the surface.

What Causes the Sailing Stones to Move

The cause of the movement of the rocks has been a matter of discussion since the 1940s.

Previous theories propose hurricane-force winds, dust devils, slick algal films, or thick sheets of ice as likely contributors to rock motion. The mechanism was described in winter 2013-2014.

Thin ice floating platforms driven by wind cause sailing stones to move. Some other factors should be met. The surface should be horizontal and slippery. The water level has to be very low and not cover the top of the rock. Nights should be cold enough to freeze the water, and days should be sunny and windy.

Sailing rocks move under very light winds of about 3-5 meters per second and are driven by ice sheets less than 3-5 millimeters thick.

The speed of movement is only 2-6 meters per minute. It is almost imperceptible at a distance and without stationary reference points, which is typical for desert.

It seems likely that sustained winds are needed to keep both the ice and liquid water of the pond in motion before the ice melts completely.

Therefore, the extremely episodic occurrence of rock motion (years to decades) is likely due to the infrequency of rain or snow events sufficient to form winter ponds.

TIP: Sailing stones look like they are alive. Do you know what the organic rocks are? The most common organic rocks are described in the article below:


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How Do Sailing Stones Move

Sailing stone movement requires a number of very specific conditions to be met. Sailing rocks are moved by thin floating ice platforms driven by slight wind during sunny winter days. Rocks are frozen into ice sheets and slide on the slippery mud bottom, which was previously humidified by heavy rains.

Observed rock movement occurred on sunny, clear days, following nights of sub-freezing temperatures. Steady light winds and morning sun caused floating ice to break up near mid-day.

Ice initially broke into floating panels tens of meters in size that became increasingly fragmented and separated by open rippled water as melting continued.

Floating ice sheets, driven by wind stress and flowing water; pushed rocks resting on the playa surface. In some cases, moving more than 60 rocks in a single event.

Rocks often moved multiple times before reaching their final resting place. The researchers also observed rock-less trails formed by grounding ice panels – features that the Park Service had previously suspected were the result of tourists stealing rocks.

BTW: Do you want to know more about rocks and minerals identification? The books listed below are the best ones you can find on the internet (Amazon links):

Where Are Sailing Stones Located & Can Be Found?

Sailing Stones in the Death Valley National Park, California
Sailing Stones in the Death Valley National Park, California

The best-known place of sailing stones is the Racetrack Playa in Death Valley National Park, California, USA.

It is the place where the movement of rocks has been observed and filmed for the first time. However, there are some other places in the world where a similar mechanism takes place.

Sailing stones can be found not only in Death Valley National Park. They are also reported from the shallow bottom of the Great Slave Lake in northern Canada, the shores of the Baltic Sea, dry lake surfaces in Spain and South Africa. The explanation of rock trails is linked to floating ice, too.

TIP: California is full of amazing rockhounding sites. Check out the best digging sites in California with maps included in the article below:


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Interesting & Fun Facts About Sailing Stones

The strange things without explanation create a lot of superstitions and fun around. Here we will describe some of them.

Sailing stones gather a lot of fun facts around. There was a theory that explained the rock movements by aliens. Another fact is that scientists who gave us an explanation of the movement of rocks said that is the most boring experiment ever, as they were forced to wait two years before any results.

Another interesting fact is that you can simulate the similar movement of rocks even at home the same way as it did Ralph Lorenz, a planetary scientist. 

He conducted the kitchen table experiment. He took a small rock, put it into some tableware, and filled it with water, so there was an inch of water with a bit of the rock sticking out. He put it in the freezer and later found a slab of ice with a rock sticking out of it.

The scientist flipped the rock-ice hybrid upside down and floated it in a tray of water with sand on the bottom. By merely blowing gently on the ice, he realized he could send the embedded rock gliding across the tray, scraping a trail in the sand as it moved. 

Don’t hesitate to conduct the same experiment at home and to get sailing rocks right in your kitchen.

FAQ About Sailing Stones (Rocks)

Still did not find the answer to your answers about sailing stones? Find frequently asked questions in the section below:

What Is the Theory of Sailing Stones

The accepted scientific theory proven by observation is that floating ice sheets, driven by wind, push the rocks resting on the mud desert surface. Surprisingly, there is heavy rain and ice in the desert in winter. The combination of events gives rise to the sailing stones phenomenon.

What Does Sailing Stones Look Like?

Sailing stones don’t differ from any other stones. They are pebble to boulder-sized pieces of dolomite and granite, which leave tracks on the surface showing the direction of motion. The sailing stones are light-colored, with a weight of up to 300kg and a flat bottom.

What Made the Sailing Stones?

Sailing stones don’t need to have a specific composition to be called sailing. It can be literally any stone, which is placed into specific conditions. A stone to be called sailing has to move on the flat surface, and leave a track on the ground behind.

What Does Sailing Stone Mean?

Sailing stone, or sliding stone, or moving rocks, means that huge boulders of rock up to 300 kg move somehow on the horizontal surface without any external help. The best-known example – is sailing stones at Racetrack Playa, in the Death Valley National Park.

TIP: Are the rocks alive? Sailing stones can move so it could be possible that certain stones can be alive. Find out more in the article below:


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Conclusion

Sailing stones have puzzled scientists for approximately eighty years. Because of the remote location of sailing stones in Death Valley National Park and its severe weather conditions, the only thing people could observe is a mystery bulldozer trail just behind the heavy stone.

Dozens of theories were developed to explain the strange observation. The seemingly surreal problem ends up having a rational solution.

The explanation is that in winter, thin ice sheets form. Wind pushes ice sections laden with even heavy rocks across the temporarily slick playa when sunlight melts the ice.

For us, who saw the pictures of boulders’ trail in a desert, it was really hard to imagine that there would be rain in winter.

Moreover, winter temperatures are so low that they even turn water into ice. These prejudices push the reveal of truth for more than half of the century.

Here is a list of incredible facts concerning sailing stones:

  1. The composition and origin of stones are not important. It can even be artificial stone placed into the right conditions.
  2. There should be heavy rains to flood the valley.
  3. The water level should be deep enough to form floating ice during cold winter nights but shallow enough to expose the rocks.
  4. The movement occurs in winter.
  5. The day of movement should be sunny and warm to break the ice into rafts.
  6. A very gentle wind is necessary to initiate the movement.
  7. The bottom should be composed of mud material to be slippery enough for movement.

Now we know the real cause of stone movement. But it still fascinates us how inventive nature can be.

TIP: And it’s rockhounding time now! But do you know what tools you need for rockhounding? Check out the list of all needed tools and equipment for rockhounding in the article below:


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