Two new theories try to explain how the crescent-shaped sand mountains persist
Michael Poliza/National Geographic Creative
No sand dune is an island.
Interactions between crescent-shaped, or barchan, dunes stabilize the mounds and explain how vast swarms of them can persist over time, two new studies find. But the studies don’t agree on what kind of interactions matter: One team argues that dunes colliding and breaking apart keeps barchan fields from growing into giant sand piles, while the other claims that dunes calving off each other are the key.
Even if they disagree, “both papers are providing convincing evidence that the generation of small dunes in a field is a very important ingredient to explain the structure of barchan corridors,” says Eric Parteli of the University of Erlangen-Nuremberg in Germany.
Barchans arise in deserts where the ground is hard and flat and strong winds blow sand in one direction. Thousands of the dunes can occupy a narrow strip. Fueled by wind, the dunes travel at different paces and can traverse up to 100 meters in a year.