Singing Dunes of Kazakhstan: Sand, Sound and the Landscape of Altyn-Emel

How can a hill of sand make music? Travellers have puzzled over the sounds of the desert for at least seven centuries, from Marco Polo in the Desert of Lop to Charles Darwin in the north of Chile, and the singing dunes of Kazakhstan put it to anyone who comes to the great dune of Altyn-Emel, a single mountain of pale sand standing alone in a desert of stone above the Ili River. When the sand is dry and on the move, the dune gives out a deep, sustained hum that local accounts liken to an organ. On Day 24 of our small group journey through the four Stans, the group visits these Singing Barchans, and this article explains what is happening inside the sand when they sing.

A dune that should not be there

The first surprise of the singing dune is simply its setting. Most of Altyn-Emel is not sandy at all. Our separate guide to the petroglyphs, burial mounds and desert mountains of Altyn-Emel describes the park as a whole; here it is enough to say that the approach crosses a gravel plain scattered with saxaul and low shrubs, and that the dune rises out of it abruptly, with nothing comparable anywhere in view. The Astana Times, reporting on the dune, which is known locally as Akkum-Kalkan, calls it the only dune in a rocky desert covered with saxaul and small shrubs.

Kazakhstan’s official tourism portal places it on the right bank of the Ili, between two stony hills, the Small and Big Kalkan, and describes it as a mountain of pure sand more than a hundred metres high and several kilometres long. Published figures for its exact height and length vary from source to source, and we have found no survey that settles them, so the safest description is the portal’s: a dune on the scale of a hill, which most visitors see first as a pale wall rising between dark rock.

How the Ili River built a mountain of sand

Every grain in the dune has a source, and both the tourism portal and local reporting point to the same one: the Ili River. The portal describes the dune as built by winds out of Ili sand between the two Kalkan hills; the Astana Times explains that a strong wind carries material from the shallow river towards the ridges, weakens as it reaches them, and drops its load in the gap between. The hills, in other words, act as a trap. Sand that would otherwise travel on across the plain is caught in the lee of the rock and piles up, season after season, into a single body.

That is the usual explanation for why the dune is where it is, and why it is alone. A desert of gravel and stone has little loose sand to give; a shallow river that leaves sandbars and banks exposed to the wind has a great deal. The dune is a deposit of the river, moved a short distance by the air.

A barchan that stays put

The tour itinerary calls the site the Singing Barchans, and the word is a local one. Britannica defines a barchan as a crescent-shaped dune formed by wind blowing mainly from one direction, with a gentle slope facing the wind, a steep slip face on the sheltered side and two horns pointing downwind. The term comes from Turkistan, where such dunes are common, and was brought into scientific writing by the naturalist Alexander von Middendorf in 1881. Britannica gives typical barchans a height of 9 to 30 metres and notes that they migrate with the wind, by roughly 1 to 100 metres a year, as sand is stripped from the windward face and dropped on the lee.

The Altyn-Emel dune breaks both rules. It is several times taller than a typical barchan, and, as the Astana Times notes, it does not wander off across the plain but stays where it is. Kazakhstan’s tourism portal describes two winds, one from the east and one from the west, constantly striking the sand mountain. A dune pushed alternately from opposite sides, and held in a trap between two hills, is a very different thing from a lone crescent travelling before a steady wind, and its stability in one place is part of what has made it a landmark.

Why the singing dunes of Kazakhstan hum

The sound is real, and it has been measured on other dunes even if, so far as we can find, no published study has yet recorded the Altyn-Emel dune itself. Booming dunes are rare, and that rarity is one reason the sound stayed a mystery for so long. The research described below was carried out on dunes in Morocco, Oman and California, and every one of them shares the same requirement: a large dune with a steep face of dry, loose sand that can be made to slide.

The physicists who have studied them agree on the basics. The sound does not come from wind blowing over the dune; it comes from an avalanche. In 2004 the French physicist Bruno Andreotti, working on singing dunes in Morocco, showed in Physical Review Letters that avalanches set the surface of the dune vibrating, and that this vibration radiates into the air as a coherent sound of about 100 hertz, loud enough to reach around 105 decibels. Two years later, in the same journal, Stéphane Douady and colleagues compared several singing dunes with laboratory and field experiments and concluded that the frequency of the sound is the frequency of the grains’ own relative motion. Above a threshold speed, some of the moving grains fall into step with one another, and the flowing layer becomes a resonating instrument.

Where the researchers part company is on what sets the note. In 2012 Simon Dagois-Bohy, Sylvain Courrech du Pont and Stéphane Douady reported in Geophysical Research Letters that a dune near Tarfaya in Morocco, whose grains fall in a narrow size range, sang consistently at about 105 hertz, while a dune near Al-Askharah in Oman, with a much wider spread of grain sizes, produced a jumble of frequencies from 90 to 150 hertz. Sieved sand of a narrow size range, set sliding in the laboratory, sang a clear note of about 90 hertz, which pointed to grain size as an important factor in the pitch.

A team at the California Institute of Technology, including Nathalie Vriend, Melany Hunt and Robert Clayton, had already come to a different answer. Working on the Dumont Dunes, just south of Death Valley National Park in California, they measured booming at a dominant 70 to 105 hertz and argued in 2007 that the note is fixed by the depth of a surface layer of dry, loose sand that rests on firmer sand beneath. That layer, they proposed, acts as a waveguide, trapping and reinforcing sound waves as they bounce between the dune surface and the denser layer below, so that the dune behaves, in the words of their later press release, like a perfectly tuned musical instrument. The debate between the two schools has not been fully settled, and it is fair to say that the science is still being written.

Visitors to Altyn-Emel often hear another explanation: that the grains become electrified by friction and vibrate. It is repeated in local reporting and travel writing, but the published physics of booming dunes has looked instead to avalanching, grain synchronisation and the layered structure of the dune.

Will the dune sing when the group visits?

Not necessarily: the dune sings only when its sand is dry and moving. Kazakhstan’s tourism portal says it sings after a strong wind, falls quiet in long spells of calm, and stays silent after rain, even in wind, because wet sand does not flow. The Caltech researchers found the same on the Dumont Dunes, where moisture that soaks into the sand erases the layering they believe the sound depends on, and where, on a December visit, they could not start sustained booming on the large dune.

That is also why people climb. An avalanche can be started by hand or foot as well as by the wind, and Darwin, in Chile, was told of a sand hill called El Bramador, the roarer or bellower, that made its noise only when people climbing it set the sand in motion. A visit to a singing dune is therefore never a performance on demand, and the dune’s silence on a damp or still day is as much a part of its character as its voice.

Spirits, drums and a sleeping devil

Long before anyone measured them, booming sands were explained by stories. In the Yule translation of Marco Polo’s account of the Desert of Lop, travellers who fall behind hear spirits calling their names, and “sometimes you shall hear the sound of a variety of musical instruments, and still more commonly the sound of drums.” Physicists still cite Polo; the 2006 study by Douady and colleagues opens by noting that it has been known since Marco Polo that some dunes can emit a loud sound. The Caltech team cited Darwin in Chile and the Mughal emperor Babur in Afghanistan among the travellers who were mystified by the booming of the desert, and Darwin himself recalled earlier reports of sounding sand on Mount Sinai.

The Altyn-Emel dune has legends of its own. The Astana Times records that a great dragon is said to sleep and snore beneath it, or that desert spirits hide within it. The oldest and most widely told legend, according to the same report, is that the dune is a sleeping devil turned into sand for his sins, who groans whenever he is disturbed. These are legends, and they are best enjoyed as such. Yet they are oddly faithful to the physics: the sound comes from within the dune, it is set off by disturbance, and on a calm day the sleeper does not stir.

Stories of this kind belong to a wider landscape. Our article on the great grasslands of the Kazakh steppe follows the nomadic world that surrounds these deserts, and for practical background on the country our answers to travellers’ common questions about Kazakhstan cover the essentials.

When does the tour visit the Singing Barchans?

In the afternoon of Day 24, after the morning’s petroglyphs and lunch, on the same afternoon as the Oshaktas stone column near the Kalkan mountains. That night the group stays at a local guesthouse (our itinerary names the Agaikum Guesthouse or similar). The rest of the day, from the drive out of Almaty to the stop at the Spring of Chokmor Valihanov, is described in our guide to the park linked above.

Is walking on the dune physically demanding?

Walking on any large dune is hard work, because loose sand gives underfoot, and a booming slip face is steep: on the dunes the Caltech team studied, it stood at about 30 degrees. The Stans tour carries a Level 3 rating, Moderate to Challenging, which our itinerary defines as being in excellent health, very mobile and active, and able to manage up to six hours a day of continuous, strenuous activity at a moderate to fast pace over varied terrain. Our itinerary does not say how long is spent on the sand itself, so ask a Tour Specialist how the visit is paced before you travel.

What does the singing dune sound like?

A low, swelling rumble rather than a tune. Kazakhstan’s tourism portal describes “a growing rumble of a low tone” when the dry sand is set moving, and The Astana Times likens the tones to an organ. Bruno Andreotti, writing about the singing dunes of Morocco, compared the sound to a drum or a low-flying twin-engined jet and noted that it can be heard up to 10 kilometres away.

From singing sand to canyon country

The dune is one stage in a sequence of landscapes. The next morning, Day 25, the route leaves the sand behind for Charyn Canyon, cut by the Charyn River into the flat steppe, and ends the day at the Kolsai Lakes, which our itinerary calls the pearls of the North Tian-Shan. Our overview of the four-country route through Uzbekistan, Turkmenistan, Kyrgyzstan and Kazakhstan shows where these final days in southeastern Kazakhstan sit within the whole journey.

Listening to the desert

The singing dune of Altyn-Emel is a meeting point of several stories. A river supplies the sand, two stony hills trap it, opposing winds hold it in place, and dry avalanches on its steep face set it humming, by a mechanism physicists in Paris and Pasadena are still refining. Around it has grown a second story, of spirits, drums and a sleeping devil, told by people who heard the sound long before anyone could explain it. On the afternoon of the visit, you can hold both in mind at once.

In a small group of up to 16 travellers, with the day’s route, meals and guesthouse arranged, you come to the singing dune in the closing week of a journey that began in Tashkent. If you would like to listen to the desert for yourself, our 28-day Stans tour from Tashkent to Almaty brings you to the Singing Barchans on the afternoon of Day 24.