Salt flats, also known as salt pans, salt playas, or dry lakes, are flat expanses of land covered in a layer of salt and other minerals.
Salt flats are typically found in areas with little rainfall and high evaporation rates, such as deserts or regions that were once covered by seas or lakes.
These areas are characterized by a cycle of flooding and evaporation, which leaves behind a layer of minerals on the surface. Over time, this layer can become several meters thick and form a hard, crusty surface.
Salt flats can range in size from small depressions to expansive landscapes that stretch for hundreds of kilometers.
Some of the largest salt flats in the world include the Salar de Uyuni in Bolivia, the Bonneville Salt Flats in Utah, Badwater Basin in Death Valley, and the Etosha Pan in Namibia.
The Salar de Uyuni is the largest salt flat in the world, covering an area of over 10,000 square kilometers. The salt flat is one of the most popular tourist destinations in Bolivia.
Badwater Basin Salt Flats is a vast expanse of salt flats located in Death Valley National Park, California. The basin is the lowest point in North America, with an elevation of 282 feet below sea level.
The salt flats are formed by the evaporation of the small amount of water that flows into the basin each year. This process leaves behind a layer of salt and minerals that forms a thick crust on the surface.
Geometric pattern of salt flats
One of the most unique features of salt flats is their honeycomb pattern.
From an aerial view, salt flats resemble a patchwork of hexagonal shapes, which has puzzled geologists for many years. The hexagonal shapes are created by the evaporation of water from the surface of the salt flats.
As the water evaporates, it leaves behind a layer of salt that begins to crystallize. The salt crystals grow into hexagonal shapes, which then expand and merge with neighboring crystals to form the characteristic honeycomb pattern.
Why do salt flats form a hexagonal pattern?
Researchers wanted to understand why salt flats, no matter where in the world or what chemical composition the dry lake is made up of, tend to form similar hexagonal patterns. Regardless of where the salt pan is located, the polygons formed always tend to be about 1–2 meters across.
What the researchers found was that the shapes that form on dry lake beds with salt are created by the movement of high and low salt water under the ground. This was found by observing and simulating the process. The water moves through convection, creating the patterns seen on the surface.
To better understand how salt flats work, scientists used a computer model that uses fluid dynamics and other geophysical principles to recreate the process.
Salt beds, despite their appearance, are in a constant state of evaporation. Water just underneath the surface of the flats is continually being pulled towards the surface by evaporation.
In a generalized sense, the difference between density of low-salinity water, which rises, and high-density saline water, which sinks, creates the dynamics that result in the geometric patterns as higher-saline water movements in the form of convection rolls to the edges of the shapes.
Buchanan, M. (2023, February 24). Why Death Valley is full of polygons. Physics. https://physics.aps.org/articles/v16/31
Lasser, J., Nield, J. M., Ernst, M., Karius, V., Wiggs, G. F., Threadgold, M. R., … & Goehring, L. (2023). Salt polygons and porous media convection. Physical Review X, 13(1), 011025. DOI: 10.1103/PhysRevX.13.011025