No. 72: Nov-Dec 1990
"The sun was sinking in the west African afternoon when we plunged into a wild Land Rover ride across the dunes. Within moments we lost all sense of direction, regaining it only momentarily when we caught a glimpse of the sea, as we sped along the notorious Skeleton Coast of Namibia. When we finally stopped, it was at the top of a crescent-shaped behemoth. On the inside of the curve, the dune was a good 200 feet high and as close to vertical as a sand dune gets.
"We gathered timidly at the edge of the precipice. But our guide, seemingly bent on suicide, sat down at the crest and started to slide down the dune face, the seat of his pants sending a small cascade of sand slithering to the bottom. Instantly, the entire dune began to pulsate, groaning and grumbling, as if armies of Frank Herbert's sand-worms from Dune were chewing their way to the surface. In a moment, all of us were laughing and scooting down the dune, the unearthly roar echoing in the natural amphitheater."
What a delightful introduction to one of Nature's light-hearted anomalies! Such booming dunes and roaring sands may be found in thirty-or-so localities all over the world, mostly in desert envi-ronments. Most of the booming dunes are composed of quartz sands, the main exception being the Barking Sands on Kauai, Hawaii, which are calcium carbonate. Despite over a century of investigation, no one knows exactly why some dunes boom. In fact, the sand grains of booming and silent dunes look pretty much alike. The addition of sand from a booming dune will not make a silent dune roar, but the additon of silent-dune sand to a booming dune will contaminate it and ruin its boomability. Glass beads of the same size as the quartz grains in a booming dune will not boom, despite their smoothness. A lot of experiments have been tried with the booming sands, but though they will boom, they won't talk! (Thompson, Sharon Elaine; "Wagnerian Sands of the Desert," Lapidary Journal, p. 26, July 1990. Cr. R. Calais)
Reference. Booming dunes and "muscial sands" are subjects covered in ESP14 in Anomalies in Geology. Ordering information here.