Divers have discovered strange chimney-shaped vents on the Dead Sea’s lake floor that discharge shimmering plumes of fluid.
The Dead Sea is a constantly changing and dynamic system. Its level is currently dropping by roughly 1 meter (3.3 feet) per year, which has been happening for over 50 years. This is because the Dead Sea is a landlocked lake, rather than a sea (despite the name), and is cut off from key tributaries. Over the years, it has been losing large amounts of water due to drought, heat, and exploitation for agriculture, which has caused it to drop to around 438 meters (1,437 feet) below sea level.
This loss has significant geopolitical implications and environmental consequences as it borders Israel, Jordan, and the West Bank under Palestinian administration. One such issue relates to the groundwater level. As this is falling, it becomes increasingly difficult for the neighboring countries to access it as a resource.
It was while investigating the dynamic nature of the groundwater system and how aquifers are changing, that divers discovered the strange chimney-like structures on the lake floor.
“These bear a striking similarity to black smokers in the deep sea, but the system is completely different,” Dr Christian Siebert, from the Helmholtz Centre for Environmental Research, Leipzig, explained in a statement.
Siebert, and an interdisciplinary team of researchers – including mineralogists, geochemists, geologists, hydrologists, remote sensing experts, microbiologists, and isotope chemists – from 10 research institutions have now turned their attention to these odd structures.
Although these Dead Sea chimneys resemble the black smokers that are seen along the mid-ocean ridge, they are quite different. Black smokers are usually located at depths of several thousands of meters below the surface, and they emit hot water that contains sulfides. In contrast, the Dead Sea stacks appear to be issuing highly saline (salty) groundwater and are much closer to the surface.
This is interesting on its own, but where does this salt water come from? It seems the groundwater surrounding aquifers – underground reservoirs – penetrates into the saline lake sediments and leeches out extremely old and thick layers of rock that mostly consist of mineral halite. This then flows into the lake as brine.
“Because the density of this brine is somewhat lower than that of the water in the Dead Sea, it rises upwards like a jet. It looks like smoke, but it’s a saline fluid,” Siebert added.
When this liquid makes contact with the lake water, the salts (and halite) dissolve and spontaneously crystallize after emerging from the lake bed and form the unique vents that have just been discovered. These vents can grow several centimeters within a single day. While many are around 1 or 2 meters (3.3 to 6.5 feet) high, some are several meters high and have a diameter of more than 2 to 3 meters (6.5 to 9.8 feet).
The researchers also found traces of chlorine-36 – a radioisotope known as a cosmogenic nuclide because it is formed from energetic cosmic rays that impact matter in a fission reaction – in these white smokers. This, coupled with the results of genetic verification of freshwater microbes in the water issuing from the chimneys, shows that white smokers originate in the aquifers in the surrounding area.
The researchers believe these white smokers can play a role as an early warning indicator for sinkholes, thousands of which have appeared along the Dead Sea in recent decades. These holes appear due to the dissolution of massive layers of salt in the subsoil (a process known as karstification). This can create giant cavities that eventually give way and collapse.
For decades, sinkholes have been appearing across the Black Sea. Now the scientists believe the white smokers may help identify where future ones will appear.
Image credit: Helmholtz Centre for Environmental Research (UFZ)
“To date, no one can predict where the next sinkholes will occur. They are also life-threatening and pose a threat to agriculture and infrastructure”, Siebert added.
Through their work, the team were able to show that the chimneys formed wherever the land surface went on to collapse over a larger area due to karstification.
“This makes the white smokers an outstanding forecasting tool for locating areas that are at risk of collapse in the near future,” Siebert said.
It is possible that autonomous watercrafts equipped with multibeam echosounders – a type of sonar often used for navigation or measuring the bottom of the sea – or side-scanning sonar systems could be used to map the chimneys with a high level of precision.
“This would be the only method to date, and a highly efficient one, for identifying regions at risk of imminent collapse”, Siebert concluded.
The paper is published in Science of the Total Environment.
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