Home > Geology > Booming Dunes

NEW! Our dunes research was featured on the premiere episode of NOVA's "Science Now" on PBS in January 2005. For a fun introduction to booming dunes, you can watch the show online on NOVA's website.

I studied booming dunes for a Caltech SURF ("Summer Undergraduate Research Fellowship") project during the summer of 2002 and enjoyed it so much that I continued the project as a senior thesis during the school year of 2002-2003. Although I've since graduated and started working on more purely geology projects, I'm still very much interested in sand dunes, and I try to tag along on field trips whenever I can.

Many desert sand dunes -- at least seven in the United States -- make loud booming noises (like a propeller airplane) when they avalanche. Records of the sound are centuries bold, but the cause of the sound remains a mystery.

There seem to be two phenomena at work: "booming" and "burping".

If you put a sample of booming sand in a jar, close the lid, and shake the jar, it will make a noise called "burping". In fact, even sand from many non-booming dunes will burp in a jar if you dry the sand in an oven first; it seems that at many dunes, the only thing preventing them from booming is a little extra moisture.

The cause of the burping sound remains a mystery. Burping sands have several unusual properties that could cause them to make noise; for instance, burping sands all have similar size distributions. Their mean grain diameter is generally between 0.2 - 0.4 mm, and they're unusually well-sorted. However, synthetic sands with similar size distributions do not boom, so size distribution can't be the only thing that matters. Dune sand, which endures millions of years erosion before ending up on a dune, is also very spherical and well-rounded; the grains' shape may have something to do with the burping sound.

"Burping sand" sings at a frequency of several hundred hertz, which is close to the pitch of a human voice. How could this mid-range sound get translated into the low, 60 - 100 throb of booming? The structure of the sand dune probably sets up a wave guide that amplifies the low frequencies. We think the sound bounces reflects off of the boundary between a top layer of loose, unconsolidated sand and a moister, more compact sand about a meter below the surface.

Dunes to Visit:

  • Big Dune, NV
  • Bodie Railroad Dunes, CA
  • Coral Pink Sand Dunes, UT
  • Dumont Dunes, CA
  • Eureka Dunes, CA
  • Great Sand Dunes, CO
  • Kelso Dunes, CA
  • Stovepipe Wells Dunes, CA
  • White Sands, NM

    • People:

  • Prof. Melany Hunt
  • Prof. Chris Brennen
  • Grad Student Steve Hostler
  • Staff Researcher Gustavo Joseph
  • Undergrad Nora DeDontney

    • Movie (with Audio):

    Here's a movie from one of our early ventures to Kelso Dunes, CA. The vignetting around the edges is probably the result of the tape overheating. (We hiked to the top around 8am to avoid the heat, but the temperature was already in triple digits.) Many speakers cannot reproduce the low frequency (~80 Hz) booming sound very well, so don't be surprised if you can't hear anything on your computer. The sound isn't audible until halfway through the clip, so be patient.