Faces Magazine, May 2006 issue.
A 9th century Chinese writer, from Kansu, wrote a strange text. It described a ‘Hill of Sounding Sand,’ which was 500 feet high in places. In peak summer, when horses or people walked over the dunes, loud and mysterious sounds came from these sands. During the Dragon festival, men and women slid down from the highest point of the sand mountain, to make it sing! Arabs have known about booming desert dunes for more than 1,500 years. Marco Polo thought that evil spirits caused strange noises in the sands of Gobi desert!
Booming sands in deserts can produce loud noises like jet planes taking off, kettledrums, galloping horse, thunder, or a truck starting up. Most beach sands ‘sing’ or squeak, as Australians call it.
Dr. John Lindsay Johnson, scientist at the Lunar and Planetary Institute, Texas, who grew up in Australia said, “The best known is Squeaky Beach in the state of Victoria. Most beaches in Eastern Australia squeak – they are just so common we took it all for granted.”
Singing sands are more common than booming sands. Scientists buried oscilloscope to study the vibrations produced by the singing and booming sands. On the oscilloscope screen, the vibrations appear in short bursts. The singing sands produce vibrations every 0.1 seconds, whereas booming sands produce vibrations about one second apart.
The dunes produce noise when sand grains bump each other. This makes a layer of sand, sometimes only 2 or 3 centimeters deep, to quiver like the surface of a boom box. Dr. Douady, a French scientist who studied singing dunes in Morocco, had samples shipped back to his lab. Here, he could make the sands sing by pushing it by hand or with a metal handle. After a month the sands stopped singing! Under the microscope, sand grains showed a smooth coating of silicon, iron and manganese. When this coating wore off, the sand could no longer sing. This explains why all sands cannot sing.
During the lunar landing, scientists heard ‘Thermal moonquakes’ in lunar craters. The noise was similar to the booming sands on Earth. On the Moon, the temperature at night is about –180 degrees Celsius. It increases to 130 degree Celsius during the day. Scientists believe that grains trapped in the cracks of the craters produce noises due to temperature variation.
Dr. David Criswell, Director of the Institute for Space Systems Operations, Texas, explains, “Booming dunes are very rare on Earth. The booming process may be common on the Moon.”
So, the next time you head to the beach, take your time. You can make the sands sing!