(ORDO NEWS) — Scientists have figured out how patterns are formed in the desert in the form of polygons.
Polygon-like honeycomb patterns occur in many salt deserts, including Death Valley in California and the Salar de Uyuni in Chile.
For a long time, scientists suspected that the salt crust of the desert dries up and forms cracks around which patterns grow.
Another hypothesis suggested that the salt crust continuously grows and bends due to lack of space, leading to the formation of patterns.
However, neither explanation made it clear why the elements of the pattern always have a constant size – from one to two meters – and also did not clarify why the honeycombs are so even and periodic.
Now American scientists were able to capture the formation of these structures on video, conducted a series of laboratory experiments and eventually revealed the secret of their formation.
The driving mechanism for pattern formation is the circulation of salt water in the soil under the salt crust.
The salt flats in which these patterns occur are not really dry: very saline groundwater often reaches the surface, lying just below the salt crust.
When this brine evaporates in the 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 and the fresher water rises from below.
Like hot and cold water circulating by convection, convection swells of salty and less salty water form in the bowels.
A single convection roll will have a circular shape that maximizes the volume contained within the roll while minimizing its circumference.
However, when many convection swells are formed in the ground next to each other, they “shrink” and form hexagonal honeycomb patterns, along the edges of which very salty water sinks.
In places with a particularly high salt content, the salt also crystallizes on the surface. Over time, the drying crust forms raised humps that create a honeycomb pattern.
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