The secret of the salt fingers of the Dead Sea

“Salt fingers” are abnormal salt crystals growing on the bottom of the Dead Sea. For a long time, scientists could not understand what exactly led to their formation, and finally they had the opportunity to lift the veil of secrecy.

For millennia, the saltiest body of water on Earth has attracted hundreds of thousands of people who want to plunge into its waters. Surprisingly, over time, the concentration of salt in this “sea” (which is actually an isolated lake on land) only increases – and this is despite the fact that water is already almost 10 times saltier than in the present sea!

This transition is mainly due to human activities: fresh water from the Jordan River, which has traditionally fed the Dead Sea, has been used for other purposes in the region in recent decades, including agriculture, mining, and drinking water. As a result, the lake water gradually evaporated, leaving behind the salt-covered salt marsh. But in these salt crystals there is something that has confused scientists for decades.

In particular, after the gradual cessation of the influx of fresh water, the researchers began to notice that the crystals precipitate from the upper water layer, and then fall into the water and accumulate at the bottom. This phenomenon is called “salt fingers”, and for a long time no one could understand why it happens in the Dead Sea, since nothing similar happened in other super-saline water bodies known to us.

“Initially, these“ fingers ”are too small to be seen with the naked eye, but they quickly interact with each other and form larger structures,” explains mechanical engineer Raphael Willon of the University of California, Santa Barbara.

The solution was very interesting. When light falls on the waters of the Dead Sea, the upper layers of the water naturally heat up. This heat is enough to start the evaporation process, which means that the upper layers of the water literally “spill it out” with the crystallized salt. But how then do they end up at the bottom? Usually warm and cold water, and even with a high salt content, mixes very reluctantly.

In a new study, Willon and his team simulated this process, triggering small waves in a salt water tank. As a result, the layers of warm and cold water began to mix, the warm water cooled and the salt rushed down. The end result was a strong downward flow of salt, with the result that the bottommost layers of the liquid became supersaturated and precipitated the salt in the form of crystals. However, these are the results of an experiment in the laboratory, and scientists want to make additional measurements and make sure that this is how the Dead Sea is covered with crystals in the real world.