Scientists have uncovered how polygon shaped patterns arise in desert salt flats, and this discovery is tied to the work carried out at Nottingham Trent University. These geometric formations resemble a honeycomb and are visible in arid regions such as Death Valley in California and the Salar de Uyuni in Chile. For years, researchers speculated that the drying salt crust would crack and radiate patterns around those fractures. Another theory proposed that a constantly growing crust with absence of voids could bend and create steady shapes. Yet the precise reason why each element of the pattern maintains a fixed size, typically between one and two meters, and why the honeycombs appear so even and periodic remained unclear until now.
American researchers captured the evolution of these structures on video, ran controlled laboratory tests, and pieced together the mechanism behind their creation. The guiding driver is the movement of salty groundwater beneath the crust. These salt flats are not completely dry. Very saline groundwater sits just below the crust and periodically rises to the surface.
As the sun evaporates this salty water, salt remains as crystalline deposits. The groundwater just below the surface becomes denser with salinity, and therefore heavier, than the fresher water deeper in the soil. Where the salinity gap is significant, the heavier, saltier water tends to sink while the lighter, fresher water ascends. This process mirrors convection currents driven by temperature differences, but in this case it is driven by salinity contrasts. The result is a vertical churn of salty material within the subsurface, sculpting the ground above.
When many of these convection cells align side by side, they form the characteristic hexagonal edging of the pattern. Each cell shrinks slightly and the edges become a network where the most salty water sinks. On the surface, in regions with especially high salt content, salt crystals accumulate and dry into a crust that lifts into bumps. Over time, these raised features interlock into a visible honeycomb of interwoven polygons.
The geometry of the system tends toward efficient packing. A single convection cylinder is circular, maximizing volume for a given footprint. But when dozens of such cells bunch together on the ground, they settle into a tessellation that optimizes space by forming hexagonal links along their margins where the densest saline layers settle. The resulting pattern is both stable and repeatable, explaining why the polygons tend to stay within a common size range and why the honeycomb appears so orderly across wide areas.
These findings not only illuminate a striking natural phenomenon but also reflect broader physical principles describing how fluids foliating a porous medium can drive large scale pattern formation. The study of saltwater convection patterns provides a tangible example of how simple processes at small scales can yield intricate and enduring macroscopic structures. This intersection of geology and fluid dynamics helps researchers predict when and where such patterns will form, and it informs models of desertification and soil stability in salinized regions around the globe. Scientific discussions and recent analyses offer corroborating observations from field sites and laboratory analogs, underscoring the reliability of the proposed mechanism and its implications for understanding arid landscapes.