The large-scale deposits of salt around the Dead Sea, known as salt giants, are built up as the lake’s highly saline water evaporates, and a new study of their formation has revealed some of the secrets of these mounds of halite.
That’s exciting for geologists, because salt giants can be found in several other places, including under the Mediterranean Sea. However, these deposits are no longer being formed, so they can’t be analyzed in the same way as the Dead Sea salt giants.
The study was carried out by mechanical engineer Eckart Meiburg, from the University of California, Santa Barbara, and geologist Nadav Lensky, from The Hebrew University of Jerusalem, and gives us some answers to long-standing questions about salt deposits, the evolution of lakes, and shifting environmental pressures.
Related: Tiny Drops of Water Trapped in Salt Hold 150 Million Years of Ocean History
“These large deposits in Earth’s crust can be many, many kilometers horizontally, and they can be more than a kilometer thick in the vertical direction,” says Meiburg.
“How were they generated? The Dead Sea is really the only place in the world where we can study the mechanism of these things today.”
The researchers used a combination of field observations, lab experiments, and computer models to figure out exactly how the Dead Sea salt deposits were forming. They were particularly keen to see how variations in salt giant formation might come about.
Numerous discoveries came out of the study. For example, the researchers found salt deposits happening all year round, not just during the winter months (as had previously been assumed).
In summer, the top layer of water experiences evaporation, cooling and sinking. As a result, salt crystals form in the top layer, which then fall as snow to the bottom, forming salt giants. This snow falls at different rates and in different ways, depending on the temperature of the water, the research showed.
The new information challenges some previous assumptions about salt giants, and shows how unique the Dead Sea is – as the lowest point on Earth’s surface, with one of the highest concentrations of salt. While this body of water may stand out, it can still teach us lessons about what might happen elsewhere.
“All of these observations provide valuable lessons for coastlines around the world with regard to their stability and erosion under sea level change,” write the researchers in their published paper.
That’s because the Dead Sea is dropping by about 1 meter (a little over 3 feet) every year. It’s something happening in many other seas and lakes across the globe, as climate change takes hold – and it’s happened to other bodies of water in the past, too.
You may not be aware, but the Mediterranean Sea almost vanished many millions of years ago, and the circumstances weren’t all that different from those facing the Dead Sea today: water flow was cut off, salinity rose, and surface water levels dropped. What’s happening in the Dead Sea gives us a window back in time.
“There was always some inflow from the North Atlantic into the Mediterranean through the Strait of Gibraltar,” says Meiburg. “But when tectonic motion closed off the Strait of Gibraltar, there couldn’t be any water inflow from the North Atlantic.”
“But then a few million years later the Strait of Gibraltar opened up again, and so you had inflow coming in from the North Atlantic and the Mediterranean filled up again.”
The research has been published in the Annual Review of Fluid Mechanics.
