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.
Why are salt flats around the world covered in a similar pattern of ridges?
- 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.
- In a new study, researchers from Austria, Germany, and the U.K. may finally have an explanation.
- Using a combination of ground sampling and computer models, they have pointed their fingers at the way salt flows up and down in the soil below this formation.
- It is important to know the underlying mechanism because salt flats have significant effects on both humans and the climate.
The study and its findings :
- The researchers began with the hypothesis that the salt on the surface is influenced by the salt flowing through the soil below.
- Imagine the soil in a salt flat: there are some ridges on the top, followed by a layer of salt, then the topmost layer of the soil, and finally the rest of the soil.
- The groundwater in the soil is saline but the distribution of salt is not uniform.
- The salinity is highest near the top of the soil and decreases 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.
Implication of the results :
- Since at least the early 1960s, scientists have offered different explanations for why the surface of dried salt lakes becomes covered with this pattern of polygonal shapes.
- Most of them have either considered above-the-surface dynamics or below-the-surface dynamics, whereas the new study shows that the polygons are formed when these two realms interact.
- The theory and the results matter because when winds blow over salt flats, they carry some of the salt with them as particulate matter.
- When this air mass reaches the ocean, it deposits the salts there.
- Such sea salt can enter the atmosphere and go on to swirl at the centre of cyclones.
- When a salt-bearing air mass reaches an inhabited area, the particles cause significant respiratory problems.
- A 1996 study characterised the salt flat of what was once Owens Lake in California the “single greatest source of particulate matter in North America”.
- To mitigate the deleterious effects of salt flats, experts have recommended covering them in a shallow layer of water, so that the salt is deposited on the surface more uniformly and less salt is carried away by winds.
- Salt suspensions are also an important group of aerosols (suspensions of fine solids in air) that reflect sunlight.
Way forward :
- We know that for some time saline lakes around the world are shrinking, including due to agriculture.
- So more accurate climate models will need to better understand the sources of salt, and the new findings describe one such source.
SOURCE : THE HINDU
Syllabus : Mains; GS1 – Geography