The Dead Sea is a landlocked body of water known for its extreme saltiness, a characteristic that makes it one of the most hostile environments for life on Earth. Located between Israel and Jordan, the lake’s surface sits at the lowest land-based elevation on the planet, well over 400 meters below sea level. This unique geography and the resulting high concentration of minerals are the direct reasons why this lake cannot support the fish, plants, and other macro-organisms typically found in freshwater or marine environments.
The Geological Foundation
The Dead Sea owes its existence to a tectonic depression known as the Jordan Rift Valley, or Dead Sea Transform. This trench was formed millions of years ago by the slow, lateral movement of the African and Arabian tectonic plates. The separation of these plates created a deep basin that became a catchment for water, trapping it far below the level of the open ocean.
The extremely low elevation of the basin is a factor in the lake’s current state. This geological setting contributes to higher atmospheric pressure and elevated temperatures in the valley. These conditions facilitate the rapid evaporation of water from the lake’s surface, setting the stage for its hypersaline condition. The lake is endorheic, meaning it has no natural outlet to the sea, ensuring that any minerals washed into it remain trapped within the basin.
The Engine of Salinity
The process that transforms the Dead Sea into a hypersaline environment is driven by a constant imbalance between water inflow and water loss. Historically, the main source of water was the Jordan River, which carried small amounts of dissolved salts and minerals eroded from the surrounding rocks. This mineral load is continually delivered into a basin with no exit.
The key mechanism for concentrating these salts is intense evaporation, a process amplified by the lake’s low elevation and hot, arid climate. While the water itself is removed through evaporation, the dissolved mineral compounds are left behind, gradually accumulating over millennia. The rate of evaporation has been estimated to be around 1,400 millimeters per year.
This water loss, coupled with the diversion of the Jordan River for human use since the mid-20th century, has led to a negative water balance. The continuous decline in water level—at a rate of over one meter per year in recent decades—further concentrates the remaining brine. The current salinity level is approximately 34.2%, which is nearly ten times saltier than the average ocean water.
The Unique Chemical Profile
The Dead Sea’s hypersalinity is not merely about the quantity of salt, but the composition, which is fundamentally different from the world’s oceans. Ocean water is predominantly sodium chloride, which accounts for about 85% of its dissolved solids.
The Dead Sea brine is characterized by a high concentration of divalent cations, particularly magnesium and calcium chlorides, along with potassium and bromide. Magnesium chloride is present in very high amounts and acts as a strong inhibitor of biological activity. The presence of these specific compounds, rather than just sodium chloride, makes the water extremely caustic and highly dense.
These unique chemical properties interfere with the basic cellular functions of most organisms, such as osmosis and enzyme activity. For a typical aquatic organism, the extreme osmotic pressure would rapidly draw water out of its cells, and the high concentration of divalent ions would disrupt protein structures, making survival impossible. The resulting brine is so dense that it provides exceptional buoyancy, allowing people to float effortlessly on the surface.
Life at the Extremes
The extreme salinity and unique chemical makeup preclude the existence of fish, aquatic plants, and other complex life forms. The vast majority of the lake is devoid of macro-organisms. However, the lake is not entirely lifeless, hosting a specialized biological community.
The only organisms capable of surviving in this polyextreme environment are extremophiles, specifically halophiles, which are salt-loving microorganisms. These include certain types of bacteria, archaea, and fungi that have evolved mechanisms to regulate the salt concentration within their cells. Halophilic archaea, for example, often dominate the microbial biomass in the Dead Sea’s upper layers.
These hardy microbes are adapted to withstand the high concentrations of magnesium chloride and the intense osmotic pressure. During rare, heavy rainfall events, the upper water layers can become temporarily diluted, allowing for blooms of green algae, such as Dunaliella. These algae are then consumed by halophilic archaea, sometimes turning the water a reddish color.