Underneath the surface of a salt desert, there are layers of water. The honeycomb patterns are created when water in the soil flows in convection “rolls” beneath the sandy crust. This process is similar to the circulation of hot and cold water in a pan when it is being heated.
Have you ever observed the peculiar pattern that forms across salt deserts?
The surreal honeycomb patterns that stretch across Salar de Uyuni in Bolivia, the largest salt flat in the world. (Photo Credit: -Sara Winter/Shutterstock)
Although it may appear as a mysterious and alien landscape from a science fiction movie, this is actually a real location – a massive salt flat, known as the Salar de Uyuni in Bolivia. It was even used as a filming location for a battle scene in Star Wars: The Last Jedi. The captivating beauty of salt deserts captivate tourists, researchers, and filmmakers alike.
But how are these “honeycomb” patterns formed in salt deserts worldwide?
To understand this, we must first comprehend what a salt flat is.
What is a Salt Desert Flat and How is it Created?
Natural salt flats are flat land areas, usually found in deserts, covered with extensive deposits of salts and other minerals. Salt flats were once bodies of water, such as lakes or ponds. Due to prolonged lack of rainfall, the ground becomes increasingly arid. The water that cannot penetrate into the ground evaporates, leaving only mineral and salt particles behind.
A salt flat often glistens like a dry white sea under the sun. The vastness of the terrain itself fills observers with awe. The honeycomb pattern on its surface adds to the sense of wonder… and has sparked much curiosity.
A still from the salt planet in Star Wars: The Last Jedi. (Photo Credit: Star Wars: Episode VIII – The Last Jedi (2017))
A salt desert may seem completely dry, but if you were to dig deep with your bare hands, you would quickly encounter a layer of water beneath the crust. However, this water is so salty that it is undrinkable!
Previous Efforts to Understand the Honeycomb Pattern
Early studies proposed that when the salt crust becomes excessively dry, it begins to crack, leading to the formation of these patterns. Another explanation suggested that when the salt crust expands too much, it bends under pressure without sufficient room to grow, resulting in a network of honeycomb-like ridges.
However, none of these hypotheses could explain why the polygonal shapes appear so similar worldwide, particularly in terms of their consistent size and shape (always 1-2 meters/3-6 feet) and the rate at which they form.
The pattern remains consistent, regardless of the variations in their environmental, geological, or chemical characteristics.
Discovering New Information
A recent study has shown that the honeycomb pattern found in salt deserts may be caused by the movement of salty water beneath the sandy surface in desert soil.
So, how does this process occur?
We are all familiar with the circular motion that occurs when water is heated. When water is heated, the hot water particles, which are less dense, rise to the surface while the cooler and denser water particles sink to the bottom. This circulation of hot and cold water in a boiling pan is known as a convection current.
In a similar manner, a convection ‘roll’ of salt and fresh water takes place directly below the salt pans. This is triggered by the difference in salinity between different layers of water.
The Driving Force: Convection Flow
As we know, saltwater is denser than freshwater. Saltier water becomes heavier than the layer of water directly beneath the ground in the salt pans. At a certain point, the saltier water sinks to the bottom while the less dense freshwater rises from below. This creates many rolling plumes of water that cover the entire area, resulting in a uniform texture in the salt flats.
Mechanism behind the mysterious honeycomb patterns. (photo Credit Physical Review)
But why do these patterns form hexagons instead of circles?
If only one convection roll occurred, the shape would be circular. However, multiple convection rolls occur simultaneously next to each other. As a result, they are compressed together, pushing each other to form these hexagonal salt patterns. The salty water then sinks down along the edges of these structures.
In a salt desert, each of these rolls or coils is 1-2 meters deep, which explains why the polygon-shaped structures have a diameter of 1-2 meters each.
In areas with high salt content, salt crystals are more visible on the surface.
A Final Thought
From Badwater Basin in California’s Death Valley National Park, Bonneville Salt Flats in Utah, to the Makgadikgadi Pan in Botswana, these surreal hexagonal patterns are a common sight. For years, it seemed like one of nature’s unsolvable mysteries.
When we observe these patterns, we can’t help but wonder how nature creates such regularity and uniformity, even in the most barren and inhospitable lands. Now, it appears that we are one step closer to finding the answer!