Sunrise on the dead sea on the coast of Israel
The “salt giants” of the Dead Sea offer a rare glimpse of the earth’s geological past.
O Dead Sea It is a meeting point for extraordinary conditions: it is at the lowest point of the earth’s surface and has one of the largest salinities in the world.
A high salt concentration also gives it an unusual density, and the fact that it is the deepest hypersaline lake on the planet gives rise to curious phenomenaoften linked to temperature that researchers continue to unravel under the surface.
In a new study, a team of researchers recently analyzed one of the most intriguing of these phenomena: the so -called “salt giants”, Huge saline deposits that are not local.
The study results were presented in a published in the magazine Review of Fluid Mechanics.
“These large deposits in the earth’s crust can extend horizontally by many, many kilometers, and have more than one kilometer thick in depth,” he explains Eckart MeiburgProfessor of Mechanical Engineering at the University of California and the main author of the article, in a UC.
“How they graduated? The Dead Sea is really the only place in the world where we can study today the mechanism of these phenomena. ”
In fact, although there are other seas with massive salt formations, such as the Mediterranean or the Red Sea, Only in the Dead Sea it is possible to observe them in formation, which allows scientists to closely study the physical processes that give rise to them-in particular spatial and temporal variations of your thickness.
Evaporation, precipitation, saturation
In the article, Meiburg and the co -author Madal Lenskyfrom the Geological Survey of Israel, describe the dynamics processes of fluids and sediment transport that currently govern the Dead Sea.
These processes are influenced by several factorsincluding the Dead Sea Statute as a Salt Water Terminal Lakewithout any flow, which makes evaporation the main form of water loss.
Over millennia, The lake has been shrinking and leave salt deposits. More recently, the construction of Dams on the Jordan Riverwhich feeds the lake, accelerated the decline of water level, now estimated at about one meter a year.
As temperatures along the water column they also play a determining role in the formation of “salt giants” and in other structures, such as the summits or salt chimneys.
The Dead Sea It was once a “meromic” lake (stresslessly stratified): Throughout the year, a superficial layer of warmer and less dense water was resting on a colder and more salty layer in depth.
“Even in winter, when the surface cooled, the upper layer was still less dense than the lower,” explains Meiburg. “And so there was a salt stratification”.
This situation changed in the early 1980safter the partial deviation of the Jordan River, which caused evaporation to exceed the entry of freshwater.
At that time, the surface salinity reached the levels in depth, allowing the mixture of both layers and transforming the lake of Meromitic into Holomitica lake that suffers annual inversions of the water column.
The Dead Sea continues to stratify, but only for about eight warmer months.
In 2019, Meiburg and his team identified a surprising process during the summer: precipitation of halite crystals, a kind of snow of salt usually associated with cold times.
Halite, also called sal-gemaforms when the concentration of salt exceeds the capacity of water to dissolve itwhich is why it tends to occur in the deepest, cold and dense layers, and especially in the winter months.
However, the investigators observed that, summeralthough evaporation increased the salinity of the surface, the salts continued to dissolve thanks to the highest temperature of the upper layer.
This phenomenon gives rise to a condition called “double diffusion”on the edge between the two layers: portions of the warmer and salty water of the surface cool and descend, while parts of the lower, colder and less dense layer, warm and rise.
As the upper layer, more dense, cool, the salts rush, creating the effect of “salt snow”.
The combination of evaporation, temperature variations and density changes in the water column, along with other factors such as internal currents and ripple, generates salt deposits in different forms and dimensionsexplain the authors of the study.
Unlike other shallower hypersaline lakes, where precipitation occurs mainly in the dry season, in the dead sea the process is more intense in winter.
This kind of “snow” all year explains the formation of salt giantsalso found in the Mediterranean – which has dried during the Messinian salinity crisis, about 5.96 to 5.33 million years ago.
“At that time, There was always some entrance flow From the North Atlantic to the Mediterranean through the Gibraltar Strait, ”recalls Meiburg.” But when the tectonic movement closed the narrow, there was no longer water.
“The sea level came down between 3 and 5 kilometers due to evaporation, creating the same conditions that exist today in the Dead Sea, and leaving behind the thickest salt crust that is still buried in the deepest parts of the Mediterranean, the researcher details.
Millions of years later, The Gibraltar Strait opened againallowing the return of the Atlantic waters, and to fill the Mediterranean again.
