Researchers have discovered a new explanation for the polygonal shapes found on salt flats by studying the movement of salt in the soil. This information is important because salt flats have negative impacts on human health and the climate.
GS I: Geography
Dimensions of the Article:
- What are salt flats?
- Study Findings
- Implications of the results
What are salt flats?
- A salt flat is a natural landscape in which a large area of flat land is covered by salt.
- Perhaps the world’s most well-known salt flat is the Salar de Uyuni in Bolivia.
- It is the largest in the world of its kind, and also contains more than half of the planet’s lithium reserves.
- A salt flat forms from a natural water body whose recharge rate is lower than the evaporation rate.
- Over time, all the water evaporates, leaving behind the dissolved minerals, usually salts. They reflect sunlight strongly and thus appear bright.
- The underlying soil is highly saline — even if the water table is shallow. The groundwater is too salty for humans to drink.
- In salt flats across the world, the salt on the surface forms ridges that join together in a patchwork of pentagons and hexagons.
- These captivating patterns have been photographed as far apart as Bolivia, Chile, China, India (in the Rann of Kutch), Iran, Tunisia, and the U.S.
- These shapes are also invariably a metre or two across.
- That the salt always crenellates in these shapes and at these sizes, irrespective of the local environmental conditions, the mineral chemistry, the soil type, and other factors has puzzled researchers.
- The researchers hypothesized that the salt on the surface of a salt flat is influenced by the salt flowing through the soil below.
- The distribution of salt in the soil is not uniform, with the highest salinity near the top of the soil and decreasing towards the bottom.
- The researchers found that the salt penetrated deeper into the soil exactly below the ridges and remained shallow under the flat areas.
- The less-dense groundwater within the convection cell is displaced upwards, carrying more saline groundwater towards the surface than through other parts of the soil, resulting in the accumulation of salt on the surface and the formation of the narrow ridges that make up the polygons.
- The mathematical equations in the computer model show that the subsurface convection is relatively insensitive to salt chemistry, and the convection columns grew to have a stable width of 1-2 m over time, which matches the dimensions of the polygons on the surface.
Implications of the results
- The new findings have significant implications for understanding the formation of polygonal shapes on the surface of salt flats and the processes that lead to the accumulation of salt.
- By demonstrating that both above-the-surface and below-the-surface dynamics interact to create these patterns, the study provides a more comprehensive explanation for the phenomenon than previous models that focused only on one aspect.
- Furthermore, the research has practical implications for mitigating the negative effects of salt flats.
- By understanding how the salt accumulates on the surface, experts can develop better strategies to control the distribution of salt and reduce the amount of particulate matter carried by winds.
- The findings may also have implications for climate models, as they describe a significant source of aerosols that reflect sunlight, and highlight the shrinking of saline lakes worldwide due to agricultural practices.
- Overall, the study represents an important step towards a more complete understanding of the complex dynamics of salt flats and their environmental impact.
-Source: The Hindu