Scientists have identified mineral formations on the floor of the Dead Sea that could warn of oncoming sinkholes. These 'chimneys' are usually about one meter (3.28 feet) in height, and they form as minerals spontaneously crystalize from the groundwater that flows out of the floor of the lake, bringing extremely high levels of salt with it. These vents were shown to be an indicator of sinkholes, which are a hazard to the communities that live around the Dead Sea. These findings have been reported in Science of the Total Environment.
"These bear a striking similarity to black smokers in the deep sea, but the system is completely different," said Dr. Christian Siebert, a hydrogeologist at the Helmholtz Centre for Environmental Research (UFZ). Siebert has been studying groundwater dynamics in the region for many years.
The black smokers on mid-ocean ridges are at a depth of several thousand meters, and release hot water that contains sulfides. But extremely salty water is coming from the white smokers on the bottom of the Dead Sea.
The researchers suggested that these white smokers are forming as groundwater from aquifers in the area seeps into very salty lake sediments. The groundwater then pushes through old and thick rock layers that are made primarily of a mineral called halite. The salty groundwater moves into the lake as brine, then the salts in the water crystalize after pushing into the lake bed, and forms the vents, or chimneys that were found.
"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," noted Siebert.
The white smokers can grow as much as a few centimeters every day, and while many slim chimneys are between one and two meters, others can grow to be seven meters high and two or three meters in diameter.
An analysis of the microbes in the water around the chimneys, as well as a radioisotope, confirms that they are from the region.
Scientists have also shown that they can act as warning signals for area sinkholes. Subsidence craters that are as much as one hundred meters wide and twenty meters deep have appeared in the region in recent decades. They happen when many layers of salt dissolve, causing the ground above to suddenly collapse.
"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," said Siebert.
In this research, the investigators showed that chimneys formed wherever the ground then collapsed over a large area. This makes the white smokers an outstanding forecasting tool for locating areas that are at risk of collapse in the near future," Siebert added.
If the area was mapped with watercraft carrying echosounders or specialized sonar systems, the places that are at risk of imminent collapse could be found, said Siebert.
The Dead Sea is one of the most unusual places on Earth. The level of this body of saline water has been consistently dropping by about one meter every year for the past 50 years at least, since it is not supplied by critical tributaries. Drought and heat are causing significant evaporation, which has led to the loss of vast quantities of water. The surface of the Dead Sea is now about 438 meters below sea level.
The loss of water is also impacting groundwater in the area, and neighboring communities are finding it increasingly difficult to access adequate water resources.
Sources: Helmholtz Association of German Research Centres, Science of the Total Environment