Sand Dunes of the Southwest

Dune Tunes

Way back in the 13th century, as Marco Polo crossed the Gobi Desert, he was haunted by unearthly noises that seemed to be coming from the sand beneath his feet. Not able to come up with a logical explanation for the sounds, he blamed evil spirits.

In deserts around the world, sounds produced by sand dunes have been variously described as booming, rumbling, roaring, droning, humming, buzzing, squeaking, whistling, singing, and musical. Often these sounds are both heard and felt, like the low sound emitted by a bass speaker. The cause of these dune noises remained a mystery for centuries, and scientists still do not fully understand why it happens.

Recent research indicates that these unusual acoustics occur when sheets of sand cascade down and rub against the stationary sand below. The friction causes the sand particles to vibrate like a musical instrument. The sand flows like liquid after being disturbed, then it begins to vibrate. The frequency of the vibration seems to be controlled by the depth and thickness of the sliding sand layer.

A 1979 report by Caltech scientist D.K. Haff explains: “…the most spectacular and enduring vibrations were produced by the movement of large quantities of sand. This could be initiated by vigorous kicking at the sharp dune crest in order to dislodge a metastable surface layer on the lee slopes.” In other words, stand at the top of a dune and kick lots of sand down the steep side!

Not all sand dunes make sounds, however, and in order to create the sound in those that do, the conditions have to be just right. The sand must be extremely dry, for example, but low moisture content alone is not sufficient to facilitate booming. The sounds also seem to be related to the shape of the sand grains, the distribution of grain size, and other factors such as surface tension and slope height.

In the southwestern United States, the best sounds can be heard at Kelso Dunes and Sand Mountain. The Eureka Dunes and Dumont Dunes also make noise under favorable conditions. In any case, it has to be a quiet day when off-road vehicles aren't racing around.

References:

http://www.pbs.org/wgbh/nova/sciencenow/3204/04-recipe.html - Recipe for Noisy Sands, from PBS Nova ScienceNow.

http://www.pmmh.espci.fr/fr/morphodynamique/SongOfDunes.html - The Song of Dunes.

http://www.schweich.com/sbdA.html - Singing and Booming Sand Dunes of California and Nevada, by Dennis T. Trexler and Wilton N. Melhorn.

http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=2588&DID=118664&action=detail - Characterization of Booming Sands, by Katherine S. Brantley, Melany L. Hunt, Christopher E. Brennen, and Steven S. Gao, California Institute of Technology.

http://www.its.caltech.edu/~nmvriend/research/ - Caltech Booming Sand Dunes Research.

http://www.its.caltech.edu/~nmvriend/research/multimedia.html - Booming Sand Dunes: Multimedia from the California Institute of Technology.

SEE ALSO:

N.M. Vriend, M.L. Hunt, R.W. Clayton, C.E. Brennen, K.S. Brantley, A. Ruiz-Angulo, Solving the Mystery of Booming Sand Dunes, Geophysical Research Letters, 34, L16306, doi: 10.1029/2007GLO30276. (2007).

N.M. Vriend, M.L. Hunt, R.W. Clayton, C.E. Brennen, K.S. Brantley, A. Ruiz-Angulo, Reply to Solving the Mystery of Booming Sand Dunes, Geophysical Research Letters, 35, L08307, doi: 10.1029/2008GLO33202. (2008).

M.L. Hunt & N.M. Vriend, Booming Sand Dunes, Annal Review of Earth and Planetary Sciences, Volume 38, May 2010.

Website design and content (c)2010 by Peter Olsen. This educational unit study was my PVCC honors project for GPH 211 Landform Processes.