A Fluid Characteristic of Particulate Matter observed in dunes collision

Geology: When sand dunes collide Nature 479, 7371 (2011). doi:10.1038/479009d Sand dunes can appear to pass through each other when they collide, confirming previous theoretical predictions. G. STEINMETZ/SCIENCE PHOTO LIBRARY Pieter Vermeesch at the University of London studied 45 years' worth of satellite images of a type of dune in Chad called barchan (pictured), and observed ten such collisions. When wind pushes a smaller dune towards a larger, slower-moving one, the small one catches up with the larger dune. Once there, the smaller dune blocks the supply of sand to the larger one such that the small one grows and slows, and the large one shrinks and accelerates. The transfer of mass means that one dune appears to move through the other as if it were a solitary wave. Geophys Res. Lett. http://dx.doi.org/10.1029/2011GL049610 (2011)