Singing Sand Dunes

http://en.wikipedia.org/wiki/Image:Kelso_Dunes_01.jpg

Walk on Kazakhstan’s Dune of Altynemel and it will sing. The sound is described as a cross between a roar and a boom; a strong wind can produce the same effect.

Singing sand is found at about 35 sites around the world, including the Eureka Dunes in California, Sand Mountain in Nevada, and the Booming Dunes in the Namib Desert of Africa.

No one’s quite sure how it works. Scientists think it’s a reverberating resonance produced by the sliding of similarly sized grains of sand.