Have you ever heard sand sing? Listen to 15 seconds of this bizarre phenomenon!

Just as our own voices are made by air moving through a vibrating vocal chords, a humming sound is made at Great Sand Dunes as air is pushed through millions of tumbling sand grains during an avalanche. Avalanches occur naturally during storms, but can also be created by people pushing sand down a dune face.
In the 1940s, one of Bing Crosby's musical hits was "The Singing Sands of Alamosa" a love song based on the sounds of Great Sand Dunes. This humming sound continues to inspire people today!
NPS/Patrick Myers