Fog, caverns and corn fields are popular settings for horror films. Why not sand dunes?
In fact, new research suggests these undulating landscapes may be capable of "communicating" their movements with one another, according to Eureka Alert.
If you live in a town or city on the edge of a desert or coastline where sand dunes form, you might understand the threat these fluid terrains can pose. Encroaching dunes can engulf roads, buildings, farms and other man-made developments with their unpredictable movements. Figuring out how they migrate is essential to planning around these natural disasters.
Now scientists have discovered that if you watch closely enough, you can decipher the secret language of sand dunes. And it turns out, dunes have been secretly coordinating their motions in ways we never knew before.
"There are different theories on dune interaction: one is that dunes of different sizes will collide, and keep colliding, until they form one giant dune, although this phenomenon has not yet been observed in nature," said Karol Bacik, first author on the new dune study. "Another theory is that dunes might collide and exchange mass, sort of like billiard balls bouncing off one another, until they are the same size and move at the same speed, but we need to validate these theories experimentally."
Bacik and colleagues have found a new explanation for dune movement, however. Using a circular dune "racetrack," the researchers employed high-speed cameras to observe how dunes separated by distance can act as if they're connected.
"We've discovered physics that hasn't been part of the model before," said Dr. Nathalie Vriend, who led the research.
It turns out, currents flowing over sand dunes can carry "information" to other dunes downstream in the form of eddies, swirls and drafts. For instance, as wind or water flows over the top of a dune, it gets deflected and turbulence patterns form. This can generate "swirls" on the back of a downstream dune and push it in a counterintuitive direction opposite the movement of the front dune.
"The flow structure behind the front dune is like a wake behind a boat, and affects the properties of the next dune," explained Vriend.
Researchers were able to provide causal explanations for some of these strange, previously unpredictable movements for the first time. The next step will be to scale up the model to capture how these swirls might become more complex when spread out over a larger and more varied dune field.
The team also hopes to get out of the laboratory and into the real world, to see if their models can be applied to dune movements in complex natural systems. They have plans to use satellite images over large deserts to track clusters of dunes over long periods, with the aim of devising ways of manipulating dune migration with artificial structures.
In other words, now that they're beginning to decipher the language of sand dunes, maybe they can start to speak it themselves and alter the dune marching orders. Imagine being able to tell a dune field exactly how you want it to move. That's the idea that this research might one day make possible.
The study was published in the journal Physical Review Letters.