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sabriel lirael abhorsen

moving rocks at death valley

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sabriel lirael abhorsen

in the California desert ther is one of the natural world's most stranege mysteries the moving rocks of Death Valley. These are not ordinary moving rocks that tumble down mountainsides in avalanches, are carried along riverbeds by flowing water, or are tossed aside by animals. These rocks, some as heavy as 700 pounds, aresome how moveds a virtually flat desert plain, leaving trails in the hard mud behind them, some hundreds of yards long. They move by some mysterious force, and in the nine decades since we have known about them, no one has ever seen them move.

Over the years, scientists have studied the rocks and proffered a variety of theories about their mysterious movements. Although there are credible theories involving wind, rain, and even ice, the exact mechanism responsible for the rocks' movement remains a mystery.

For decades, people have traveled to this remote and inhospitable region to see the bizarre rock trails, which are located in Racetrack Playa, a dry lakebed in Racetrack Valley in the northwestern hinterlands of Death Valley National Park. Hobbyists, UFO hunters, tourists, university geology students, and serious researchers have all held hope of prying answers from the valley floor. No one had undertaken a comprehensive survey of all the known moving rocks and their trails until 1993, when researcher Paula Messina set out to do just that.

A Beach in the Desert

Messina is an assistant professor of geology at San Jose State University in California. A native of New York City, she was immediately captivated by the openness and remoteness of Racetrack Valley. After miles of bone-jostling driving along a narrow dirt road, one beholds a vista of steep, jagged peaks surrounding a dry, oval lakebed, Racetrack Playa. It takes its name from its oval shape that resembles a racetrack. Playa is Spanish for "beach"-- a semantic salute to the fleeting lake that forms when rain inundates the valley.

Even the keenest human eye cannot discern any feature on this playa. It is so flat that only precision surveying instruments can identify changes in grade. But from the very southern end of the dry lakebed, a long ridge of striated, twisted rock rises to meet the base of a girthy mountain. In the shadow of the ridge, at the southern end of the lakebed, several rocks lie strewn across the hard, sun-baked earth.

Behind the rocks--some small, some the size of boulders--are the tracks, hardened into the playa surface as if the rocks had been bulldozed across a once muddy lakebed and then "fossilized" by the desert sun. But nowhere is there a trace of what propelled the rocks--no footprints, no tire tracks, nothing to reveal the bulldozer that pushed hundreds of pounds of dolomite rock, or why.

"It's hard to imagine that anyone can go to the Racetrack and not wonder why and how the rocks move," Messina says. The rocks captivated her. She said her decision to study them seemed only natural after her first intriguing visit to Racetrack Playa many years ago. "I was immediately hooked. Going there for the first time was one of those pivotal moments in one's lifetime."

Answers in the Wind

Although nobody has ever actually seen the rocks move, all substantial research clearly identifies wind as the engine that drives them. But for these stones to shove off, they need more than just extreme and sustained winds. Their vagabonding requires the right combination of conditions to act in concert-- possibly in perfect harmony. Determining that combination of conditions has been the subject of great debate, conjecture, countless hours of theorizing, and exhaustive study by researchers through the years.

The valley in which Racetrack Playa lies is about 30 miles east of the crest of the Sierra Nevada mountain range. Summer days are clear and hot. Spring and fall are, for the most part, free from storms, and winter is defined by cool days, frigid nights, and occasional precipitation--mostly rain, but sometimes snow.

The playa sits at a relatively high altitude for the region. At 3,710 feet above sea level, the playa floor doesn't experience the extreme heat that characterizes the lower reaches of Death Valley. It also sees more precipitation and dramatically lower temperatures in winter.

A small pass at the southwestern end of Racetrack Valley acts as a huge natural funnel through which tremendously powerful winds frequently blast. The winds of Racetrack Valley have created features called "ventifacts," rocks deeply etched by sand accelerating past in hurricane-force gales. Wind force here can be tremendous.

Long-term studies of the moving rocks show that they move predominantly in a southwest to northeast direction, in line with the winds. But some rove from north to south. Some head west. Many carve zigzag paths along the playa, and some have even made complete circles.

Counting Stones

Between 1993 and 1997, Messina and her team made 18 visits to the Racetrack. Employing technology unavailable to their predecessors, they mapped and measured the locations (and relocations, as many of the rocks moved during this period) of the Racetrack's mysterious rocks. They used a differential global positioning system to attain accuracy down to approximately one foot and a digital version of a highly detailed topographic map. Messina also looked at other factors, including playa constituents, wind velocities, and temperatures at Racetrack Playa. The team also took their tools to other moving rock sites. In all, there are nine in Nevada and California.

During her fieldwork at the Racetrack, Messina mapped, photographed, and measured 162 rocks and their trails (over 10,000 unique data points). In keeping with a tradition established by researchers in the late 1960s and early 1970s, Messina assigned each rock a female name.

In analyzing their massive collection of data, her team made some dramatic discoveries, not the least of which was that the phenomenon demonstrates an almost total lack of order. There seems to be no general rule for how the rocks move, either on their own or in relationship to one another. Also, Messina found no relationships among the rocks' size, shape, composition, or weight and the type of motion (straight versus curvy) or distance traveled. "Countless efforts to establish statistically significant relationships between rocks, trails, and terrain characteristics yielded disappointing results," she writes in her study. "However, this in itself may be considered one of the project¹s accomplishments."

Rock History

Prehistoric wanderers and early explorers may very well have noticed the moving rocks, but the first known sighting was made by Joseph Crook, a mining prospector from Fallon, Nevada, in 1915. He showed his wife the strangely juxtaposed rocks and their mysterious trails; the surreal phenomenon immediately mesmerized Mrs. Crook. She marked the location of one of the rocks with a stake, which was later useful in measuring the distance and direction of the rock¹s next journey.

The first published account of the moving rocks of Racetrack Valley was a brief mention in part of a 1948 abstract on the geology of the region. The authors made no measurements but put forth their idea on the cause of the phenomenon: strong, gusty winds (such as those that cause dust devils) blowing the rocks along the playa surface after it had been inundated by water. Nevertheless, it remained unclear how wind alone could move rocks of such size along such long paths.

Over the next few years, other researchers visited the playa to measure, mark, and monitor the rocks. After eliminating factors such as vibration, playa tilting, magnetism, and water currents, they focused on the combination of extreme winds and inundation by water from isolated thunderstorms.

One researcher, Thomas Clements, acknowledging that Racetrack Playa was not necessarily unique in its composition and climate, set out to see if the phenomenon occurred on other, similar desert playas as well.

Clements traveled to a Nevada lakebed called Little Bonnie Claire Playa in January 1952 and, after a careful sweep of the playa, found three rocks that had apparently moved, although their trails were much fainter than those of Racetrack Playa. Clements returned to Little Bonnie Claire Playa a few months later, in March, and camped there during a vicious rain and windstorm. He arose the next morning to find about a half-inch of water covering the playa. He walked onto the surface and found it so slippery that he could barely keep his balance. After a search, he observed a number of new rock trails of varying lengths and paths.

Clements had been pondering two possible scenarios for rock movement, and the slippery surface he found after the rain supported them both. The first hypothesis was that after an inundation event, the clay in the playa surface becomes extremely slippery, allowing high winds to move a rock.

Slippery When Wet

An important factor in Racetrack Playa's geology is that water, both from rainfall and meltwater, never makes it to the ocean-- it runs off the mountains and collects in the low-lying basins. As water flows down the mountains, it picks up chunks of rocks, ranging in size from boulders that are larger than a house (during extreme flash floods over very steep terrain) to pebbles, sand, and microscopic minerals and clays.

Typically, the largest stones are left at the top of the mountain as the grade lessens and water flowing downhill loses speed and power. The finest particles are carried all the way to the valley floor. Over many thousands of years, infrequent desert rains and spring melts have slowly deposited clay from the surrounding mountains into the valley between them, creating the playa that exists today, layer by layer.

When Racetrack Playa is dry, its surface is tough and seems about as conducive to sliding as sandpaper. When wet, however, the clay transforms as water flows between the particles (which appear as flat plates beneath a microscope) and allows them to glide past one another nearly without friction. After a good soaking, the upper surface of Racetrack Playa "swells," its numerous cracks disappear, and it becomes one of the most slippery surfaces known.

The long, beautifully striated ridge at the southern end of the playa is the northernmost part of Hunter Mountain, which defines the southern end of Racetrack Valley. Known to many as "Moving Rock Ridge," this stone phalanx, composed primarily of dolomite, is the source of the majority of the moving rocks. Natural weathering breaks off chunks of the ridge, and gravity delivers the chunks to the surface of Racetrack Playa. From there, they are ready to embark on their bizarre adventures.

Clements's theory that the playa surface became slippery enough for the wind to push them along seemed plausible. But Clements had another theory as well, one that would grip moving-rock researchers in a heated debate for many years to come. That morning at Bonnie Claire, he noted that snow had fallen on the surrounding mountains, nearly falling on the playa surface. If temperatures had dropped enough during the night to form ice, that would support his second hypothesis, which added the formation of an ice sheet to the equation. After an inundation by rain, Clements suggested, falling temperatures would lock one or more rocks in a thin sheet of ice at the surface of the water. The added buoyancy of the floating ice, he reasoned, would dramatically reduce the force necessary to move rocks across a playa.

However, he wasn¹t convinced that the ice- floe theory was correct. At Bonnie Claire, he had noted that each rock that had moved seemed to have taken its own path, independent of the other rocks' movements. Had a sheet of ice formed, he reasoned, two or more of the rocks trapped in ice would have moved in unison. But he had observed many rocks that didn't move at all, and of the ones that did, each described a unique path. Clements concluded that ice was not necessary for the rocks to move.

Two Persistent Theories

But the debate had been launched. In 1955, researcher George Stanley published a paper supporting the ice-floe hypothesis, citing precise measurements he had made of multiple parallel tracks inscribed by rocks. The noted rock trails maintained their relative positions along much of their paths, including zigzags, turns, and straight lines.

Stanley also cited another event to further support the ice-floe hypothesis. In December 1952, a large, wind-driven ice sheet had yanked 20 telephone poles out of their foundations and toppled them into a remote Nevada lake. He felt that if wind and ice could topple telephone poles, then certainly the combination could move rocks-- even rocks weighing hundreds of pounds-- across a wet, slippery playa surface.

The next few decades of research included attempts to model the wind forces necessary to move rocks of varying sizes, refinement of the two primary theories, and even a new theory that claimed wind had nothing to do with the motion of the rocks. This theory, devised by

E. Creutz, stated that the playa surface swells differentially when inundated by water, causing slippery mounds to form, which the rocks slide down. Little evidence exists to support this theory, however.

Two camps formed around the debate. The "wind-and-water alone" camp spent years studying the rocks, even corralling a group of rocks in a pen in an attempt to disprove the ice-floe theory. The ice-floe theorists cited many cases of parallel tracks among the rocks. They even artificially flooded an area of the playa and used an airplane propeller to try to set the rocks in motion, in an attempt to disprove the "wind- alone" theory.

John Reid, a professor at Hampshire College in Massachusetts, is an ice-floe theorist who brought a team to the playa to weigh and measure the rocks in the mid-1990s. After artificially saturating the area with water, Reid and his team tried to determine what kind of force would be necessary to move the rocks. Reid said that it would take at least 500 m.p.h. winds for even the smaller stones to move. Such winds have never been recorded on Earth. Reid contends that ice is in fact necessary to move the rocks.

But Messina believes that her research confirms those first theories put forth in 1948-- that strong, gusty winds alone do indeed blow the rocks along the playa surface after it has been inundated by water. She cites the chaotic pattern of tracks and splash marks in the dried mud as evidence that ice is not a factor.

It remains to determine what other factors influence the rocks' movements. Why do some move while others do not, and why do they take the mystifyingly random paths they take? One of Messina's research associates, Eric Garcia, is working on re-creating the conditions of Racetrack Playa in a wind tunnel to perhaps chip away at some of these questions.

Of course, some researchers suggest placing a video camera at the site to catch the rocks in action. But Racetrack Valley is part of a wilderness-protected area, and such intrusive monitoring is not allowed.

Messina isn't convinced that that approach would work anyway. "Before the area was deemed wilderness, an anemometer tower had been erected, in the 1950s, I believe, to quantify the wind speeds. The only problem was that the wind blew the anemometer tower down. So perhaps the videotape idea is futile, too." One must also wonder about setting sensitive equipment and live observers out in the desert under conditions violent enough to scar rocks and move 700-pound boulders.

Besides, Messina says, "I don¹t want the Racetrack to become an 'outdoor laboratory.' I know that having equipment all around would greatly hinder the experience for people who come there, as I did, to observe a unique phenomenon."

For now, visitors to Racetrack Playa can come with the dream of potential discovery. Since no one has ever seen the rocks move, anyone has the chance to be the first. Someday, someone is certain to witness the event firsthand. Perhaps that someone will even be fortunate and insightful enough to capture it on videotape. But until then, the rocks move alone, in secret, without anyone's seeing. As Messina says, "I like the idea that some things are unknowable, even if they are unknowable only a for a time."

(the above is fomanother website)

its weird rocks jus moving on thre own it so strange the feeling that rockswich u somtimes chuck around are actualy moving of thereown acord what do you think

Edited by sabriel lirael abhorsen

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zandore
Only recently, however, has a viable scientific hypothesis been given to explain how 300-kilogram stones ended up near the middle of such a large flat surface. Unfortunately, as frequently happens in science, a seemingly surreal problem ends up having a relatively mundane solution. It turns out that high winds after a rain can push even heavy rocks across a momentarily slick lakebed.
Moving Rocks

user posted image

The wind

EDIT: Welcome Sabriel to UM forums!

Edited by zandore

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LISTENintheDARK

That is really interesting. I have never heard about this before.

I'm sure it could be filmed: pay students to camp out in the season mostly to get rain, and get ready to film.

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different

It's caused by many small earthquakes is not it?

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zrina11

No. It's the wind. And temerature changes, I think. i watched something on TV ages ago.

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NoTC

Death Valley is a pretty interesting place. I've been to the racetrack playa... pretty cool. Windy as hell out there too. My first guess when I went down there, after experiencing the winds (not gas), was that the rocks were pushed slowly across the track after it rained.

I was a bit p***ed off to see tracks from people offroading on the playa and ripping up the floor, as it takes a long time for it to be restored back to it's natural state. People just can't leave things alone.

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fantazum

No. It's the wind. And temerature changes, I think. i watched something on TV ages ago.

wonder why nobody has tried time lapse photography. This would solve the mystery at a stroke.

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NoTC

wonder why nobody has tried time lapse photography. This would solve the mystery at a stroke.

Too much wind out there. It'll knock over light poles, so setting up a camera would be a bad idea.

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fantazum

Too much wind out there. It'll knock over light poles, so setting up a camera would be a bad idea.

time lapse photography has been used in antarctica to monitor the movements of shelf ice and the great barrier over periods as long as 12 months under conditions which involve hurricane force winds, blizzards and temperatures as low as -50c.

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vincecate

There is a good youtube.com video on Racetrack Playa. It shows the valley and the rocks. They also show water blowing across the valley. They say that at night it drops below freezing and large sheets of ice are blown around on top of the water and these push the rocks. They did not do the night video and actually show the rocks moving, but this is a very reasonable explanation:

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sixxx
I read up on this awhile ago. It just seems odd that wind can move such heavy stones. I wish that some one would use time elapsed photography to record the movements, that would be worth seeing.

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Legatus Legionis

hmm pretty interesting indeed.

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swtp

The documentary i watched a few years ago also explained it as wind moving the rocks, especially when it rains they said the ground is as slippery as ice! But even when it doesn,t rain and the ground is dry the winds can get strong enough to blow them a fair distance! I just wonder if the wind is too strong for a camera to be mounted and stay put, has anyone ever tried being out there in person to catch the action with their own eyes? Mabey take a big, heavy RV out there and stay up all night, point the cam. out the window and see what happens? Just a thought!

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questionmark
I read up on this awhile ago. It just seems odd that wind can move such heavy stones.

The wind moves even heavier ships. All depends on the surface the wind attacks and its speed.

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Taylynn

It seems that the best theory (that is, the most easily believed) is the whole "slippery when wet" idea. But in truth, out in the desert, you can never really tell whats going on... which is why I think the time-lapse capture is a fantastic idea. :)

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AztecInca

Moved to appropriate section of the forum. :tu:

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Maxeng

I think this is caused by freezing and thawing water under the rocks. Each time there is a freeze the rock moves maybe only a few millimeters. There are 2 possiblilities: The shape of the rock allows more ice to buildup on on one end or the rocks are creeping downhill assisted by gravity. Downhill creep by frost action is well documented, but it happens to soils. There is no reason that it could not happen under rocks as well. This is not wind, unless the wind always blows in the same direction. Only freezing would cause the rocks to travel in the same direction. If the shape of the rock is influecing the direction this could be tested by rotating a rock 90 degrees and see if it changes direction accordingly.

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