The vast majority of the planet’s water is contained within the oceans, which possess a relatively uniform salt concentration. However, certain isolated environments on Earth feature water with salt levels far exceeding the ocean average. These extreme aquatic systems are known as hypersaline bodies of water. The concentration of dissolved salts in these locations varies dramatically, creating unique geological and ecological phenomena.
Understanding Salinity and Measurement
Salinity is defined as the concentration of dissolved salts in a body of water, a property that affects density, freezing point, and the ability to support life. This concentration is commonly quantified using parts per thousand (PPT) or practical salinity units (PSU), which represent the grams of dissolved material found in one kilogram of water. For context, the world’s oceans maintain a consistent average salinity of approximately 35 PSU (35 PPT or 3.5% salt by mass). Modern measurements often use the Practical Salinity Scale (PSS-78) and are determined by measuring the water’s electrical conductivity.
The World’s Most Extreme Body of Water
The title for the saltiest naturally occurring body of water on Earth belongs to Don Juan Pond, located in the McMurdo Dry Valleys of Antarctica. This small, shallow pond is one of the most chemically unique aquatic environments known. Its recorded salinity levels frequently exceed 400 PPT (40%), making it more than ten times saltier than seawater. The pond’s extreme chemistry is dominated by calcium chloride, rather than the sodium chloride that characterizes ocean salt. This high concentration drastically lowers the water’s freezing point, keeping the pond liquid even when ambient air temperatures plummet to -50 degrees Celsius.
Comparing Other Famous Salt Lakes
The Dead Sea is often the first location considered when discussing salty waters, and it is a formidable example of hypersalinity. Situated between Israel, Jordan, and Palestine, its average salinity hovers around 340 PPT (34% salt). This high concentration is responsible for the famous, effortless buoyancy experienced by swimmers. The Great Salt Lake in Utah, the largest saltwater lake in the Western Hemisphere, presents a wider range of salinity due to fluctuating water levels. Its concentration can vary dramatically, from 50 PPT to over 270 PPT in its northern arm, depending on the season and water inflow.
Environmental Factors Creating Hypersalinity
The formation of hypersaline environments requires a specific combination of geological and climatic conditions. A primary factor is the presence of a closed basin, also known as an endorheic system, which means water flows in but has no outlet to the sea. Water can only leave these basins through evaporation, preventing the salts from being flushed out. High evaporation rates, typically found in arid or semi-arid climates, are the driving force that concentrates the salts left behind, steadily increasing the overall salinity. The balance between the rate of water inflow and the rate of evaporation dictates the final, stable salt concentration of the lake, while the specific type of salt depends on the surrounding geology and mineral input.