The Dead Sea: A Warning from the Past

A drilling project in the Dead Sea has revealed findings regarding the region's climate history and concerns about the problematic future expected of it

Mary-Ann Gurevich | Galileo

An international project of drilling in the Dead Sea, in which researchers from the Freddy and Nadine Herman Institute of Earth Sciences at the Hebrew University are participating, opens a window into the climatic and seismic history of the Dead Sea in the last hundreds of thousands of years.

The sedimentary rocks that accumulated during these periods of time under the floor of the modern Dead Sea store information that allows us to reconstruct the climate conditions that prevailed in the area of ​​the drainage basin, and even in more remote areas such as the Sahara and Arab deserts. In the drilling project it was found that about 125,000 years ago the sea dried up almost completely as a result of the climate conditions. This finding raises concern about the current state of the Dead Sea, when climate change and human intervention accelerate the drying process.

The sea remembers everything
Professor Mordechai Stein from the Israel Geological Survey and the Institute of Earth Sciences at the Hebrew University, one of the researchers working on the drilling project, says: "The Dead Sea is a salty lake, located in a deep tectonic depression (the Dead Sea rift) from which the water exits only through evaporation. The Jordan River and the Arava River transport silt and water to the Dead Sea from a very wide drainage basin, extending from Mount Hermon in the north to the Gulf of Eilat in the south.

Thanks to the drift, the Dead Sea serves as a repository of information about the environmental processes occurring in the area of ​​the drainage basin. This region includes two climatic zones - deserts to the south, and a Mediterranean climate to the north. In the last hundreds, thousands and tens and hundreds of thousands of years, natural climate changes have occurred in these climate zones. These changes left their mark on the sediments that sank in the Dead Sea and in a series of lakes that preceded it. For example, during the period called the last ice age (between 70,000 and 14,000 BC) the climate was more humid in the northern part of the drainage basin of the Dead Sea and large amounts of water filled the lake, which was called the Lake of the Tongue at that time. The levels of the tongue lake were about 200 meters higher than the levels of the Dead Sea during the Holocene period (the last 10,000 years).

On the other hand, there were events in the history of the lake where its levels dropped significantly below the current level. Such events indicate prolonged droughts and extreme dryness in the drainage basin. Extreme dryings of the Dead Sea occurred as mentioned about 125,000 years ago as well as about 13,000 years ago. The Dead Sea rift area focused the development of human activity over hundreds of thousands of years, and was probably an important route in the migration of prehistoric man on his way out of the African continent. The climatic changes in the drainage basin of the Dead Sea lakes accompanied, and probably influenced, the development patterns of human culture."

Prof. Mordechai Stein (pictured): The Dead Sea serves as a repository of environmental information. Photo: Alyssa Kagan

warning sign
As part of the drilling project, a special rig with drilling equipment suitable for extracting cores of sedimentary rocks from the bottom of lakes was brought to Israel. The drilling itself was carried out between November 2010 and March 2011 at two sites: in the center of the Dead Sea - at a water depth of 300 meters, and on the edge of the Dead Sea near Ein Gedi beach. A preliminary analysis of the drilled material shows that the cores produced in the center of the Dead Sea consist of sequences of salts and "muddy" material, indicating very dry and wetter periods respectively, in the drainage basin of the Dead Sea.

Among the exciting initial discoveries: evidence of the existence of colonies of microorganisms up to a depth of 150 meters below the surface of the ground, as well as a sequence of salts with a total thickness of about 45 meters at a depth of more than 200 meters below the surface of the ground, above which a layer of pebbles indicates the presence of a nearby beach. This finding indicates a significant drying of the Dead Sea in the past.

Scientists have shown that the sea will probably stabilize at a depth of about 550 meters below sea level (today it is at a depth of 426 meters below sea level) and will not dry up, but "the evidence of significant drying and natural retreat in the past of the Dead Sea is a warning sign against significant drying in the future. In the past, the Dead Sea was restored naturally following the renewal of the hydrological activity of the drainage basin, but such restoration of course requires the restoration of the activity of the natural system of the flow of the Jordan River, which is currently inhibited as a result of the water consumption of the countries of the region", concludes Professor Stein.