(ORDO NEWS) — For the first time, researchers have been able to explain the origin of the mysterious honeycomb patterns found in salt flats around the world.
Salt deserts are some of the most extreme and inhospitable places on the planet, and their strange and wonderful polygonal structures attract hundreds of thousands of tourists every year.
They are found in places such as the Badwater Basin of Death Valley in California and the Salar de Uyuni in Chile, where they served as the backdrop for the desert planet Crait in Star Wars: The Last Jedi.
Now a team of researchers from Nottingham Trent University and TU Graz in Austria have been able to explain the origin of these patterns and their legendary shape and size.
Previously, it was assumed that the salt crust in the desert dries up and cracks form, around which patterns grow.
According to another hypothesis, the salt crust grows continuously and, due to lack of space, bends, forming patterns.
However, none of these explanations account for the constant size always between one and two meters and the shape of the honeycomb.
Now the researchers have offered a more plausible explanation by describing how salt water convection in the subsurface is responsible for the formation of honeycomb patterns.
According to them, this can explain the constant size and growth rate of the patterns.
To unravel this conundrum of nature, the team combined fluid dynamics research from physics and geomorphology from geosciences and studied the phenomenon from multiple angles.
They observed in laboratory experiments how salt water moves in sandy soils and analyzed the scale of patterns under various conditions using numerical simulations.
In two field studies in California, they observed patterns in nature and collected samples to show that currents in the interior mirror patterns seen on the surface.
They became the first research team to videotape a salt pattern growing.
Evidence collected by researchers through experiments, simulations, and field studies points to a unified picture.
The driving mechanism for pattern formation is convection or the circulation of salt water in the soil beneath the salt crust.
The salt flats in which these patterns occur are by no means dry, and the very saline groundwater often reaches a level just below the salt crust.
In such deserts, you will quickly reach this water if you dig the earth with your hands, although it will be too salty to drink.
When this brine is then evaporated under the hot summer sun, the salt remains. This makes the groundwater immediately below the surface more saline and therefore heavier than the fresher water still lurking below.
If this difference in salinity is large enough, the saltier water near the surface begins to sink down while the fresher water rises from below.
Like hot and cold water circulating by convection in radiators, convection shafts of salty and less salty water form in the bowels.
The single convection roller is round in shape to maximize the volume contained in the roller while minimizing its circumference.
However, when many convective swells develop in the ground next to each other, they “shrink” together and form hexagonal, honeycomb-like patterns, along the edges of which very salty water sinks down.
In places with a particularly high salt content – salt also crystallizes more on the surface. Over time, the resulting crust forms raised edges and bumps, which create a honeycomb salt pattern.
First author of the study, Dr Jana Lasser of TU Graz, said: “This is a great example of fundamental research driven by curiosity.
Nature presents us with an obvious and fascinating mystery that stimulates our curiosity and thereby encourages us to solve it – even without any direct opportunity to further applications”.
In addition to satisfying curiosity, understanding the topography of salt flats helps predict how much mineral-rich dust will be knocked off the surface of salt flats and lifted into the atmosphere.
This dust, in turn, plays an important role in the formation of clouds and the transport of minerals to the oceans.
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