The not so simple life of barchans
Research uncovers their dynamics and interactions.
Sand dunes aren’t just simple piles of sand, as we’ve noted before in
Cosmos.
Earlier this year we reported on research suggesting they can “communicate” with each other to avoid collisions; currents created by one will control the movement of another.
Now Brazilian researchers have found that barchans, the distinctive crescent-shaped dunes with horns, in fact have five basic types of interaction: chasing, merging, exchange, fragmentation-chasing, and fragmentation exchange. And collisions are involved.
The good news, according to Erick Franklin from the University of Campinas, is that the same formation and interaction dynamics apply regardless of size.
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IMAGE: Researchers at the University of Campinas conducted more than 120 experiments with dunes of up to 10 cm that interact for a few minutes, obtaining a model valid for dunes. view more
Credit: Agência FAPESP
Barchans are crescent-shaped sand dunes whose two horns face in the direction of the fluid flow. They appear in different environments, such as inside water pipes or on river beds, where they take the form of ten-centimeter ripples, and deserts, where they can exceed 100 meters, and the surface of Mars, where they can be a kilometer in length or more. If their size varies greatly, so does the time they take to form and interact. The orders of magnitude range from a minute for small barchans in water to a year for large desert formations and a millennium for the giants on Mars.