Six years ago, a patch of land in the Inner Mongolian desert became unnaturally flat. Researchers, for the sake of science, had razed 40 acres — or the equivalent of eight city blocks — of desert. Then, for three and half years, they set up cameras and watched as small piles of sand grew and grew into full-fledged sand dunes.
There's already a theoretical model for how sand dunes form, but dunes are ridiculously hard to study close up. "At a minimum you need a wind tunnel hundreds of meters long, and it quickly becomes impractical to study dunes in a lab," geophysicist Douglas Jerolmack told LiveScience. All the theoretical maths was finally confirmed by this bulldozing study, which was just published in Nature Geoscience.
At this particular site, wind predominantly blew in one of two directions during different times of the year. While the sand dunes were still small, their orientation changed with the shifting winds and seasons. But as they matured, the dune's final orientation were the average of the two.
This all might seem obvious — it's what the theoretical model said, anyway — but it's far more interesting to imagine what this means in reverse. Instead studying of how wind forms sand dunes, we can reverse engineer wind patterns from the shape of sand dunes.
And so in places where we don't have weather reports — like Mars, Venus, or Saturn's moon Titan — looking at the sand could be one way to divine the patterns of the atmosphere. [Nature Geoscience via New Scientist, Phys.org, and Live Science]
Giant dune with superimposed bedform near a lake of the Badain Jaran Desert also courtesy of Clément Narteau.
Lead image: Incipient sand dunes in Inner Mongolia China courtesy of Clément Narteau.