|05 February, 2012 |
| Omen for the future: the Dead Sea was nearly dry generations ago, drilling project shows |
| Prof. Mordechai Stein of the Geological Survey of Israel and the Hebrew University of Jerusalem |
The rapidly dropping water level of the Dead Sea, a cause of much concern today, occurred as well in the distant past, resulting in the severe drying up of the lake, an international drilling project there has shown.
The project, in which researchers from the Fredy and Nadine Herrmann Institute of Earth Sciences at the Hebrew University of Jerusalem were involved, opens a window into the climatic and seismic history of the Dead Sea over the past hundreds of thousands of years.
The project discovered that about 125,000 years ago, the lake had dried up almost completely as a result of climate change. This finding arouses worry about the present status of the Dead Sea – the lowest place on earth -- in which human intervention is causing acceleration of the drying-up process.
A special rig was brought to Israel for the purposes of the drilling project, including equipment to bring up sediment samples from beneath the lake floor. The drilling was done from November 2010 until March 2011 in two areas: in the center of the lake at a depth of 300 meters and near the Ein Gedi shore.
The drilling was done under the auspices of the International Continental Drilling Program (ICDP) under the direction of Prof. Mordechai Stein of the Geological Survey of Israel and the Hebrew University and Prof. Zvi Ben-Avraham of Tel Aviv University, with support from the Israel Academy of Sciences and Humanities.
Other partners in the project were researchers from the Hebrew University’s Fredy and Nadine Herrmann Institute of Earth Sciences: Prof. Amotz Agnon, Prof. Yehouda Enzel, Prof. Boaz Lazar and Prof. Yigal Erel.
The Dead Sea is a salt lake located in a deep tectonic depression – the Dead Sea basin -- in which the loss of water is only through evaporation. The lake behaves like a large water gauge of its watershed. The Jordan River and the Arava stream transport sediments and waters from north and south that reflect the environmental conditions in the Mediterranean and desert climate zones.
Over the past hundreds of thousand of years, the lake accumulated information on the hydrological–climate conditions in these regions. Moreover, the reconstruction of climates of the past are relevant to human history since the Dead Sea basin is located along a major route for pre-historic man on his way out of Africa.
The sediments that were drilled and recovered from the floor of the Dead Sea contain the information that enables us to reconstruct the climatic conditions that existed here and even in more distant areas such as the Arabian and Sahara deserts, said Stein.
A preliminary analysis of the drilled cores discovered, at a depth of 250 meters below the lake floor (and 550 meters below the lake surface), thick sequences of salt covered by rock pebbles that indicate a period when the lake retreated and nearly dried up. These sequences are overlain by marly (muddy) sediments that indicate, conversely, an enhanced input of freshwater to the lake and wetter climate conditions in the watershed.
Today, the Dead Sea is at a level of 426 meters below sea level and sinking rapidly. The evaporation of the lake in the past should be a warning sign for us now in terms of a possible drying up in the future, say the scientists. Whereas in the past, forces of natural climate change brought about a refilling on the sea through drainage of waters coming into the basin, this cannot happen as long as the waters of the Jordan River are diverted by its neighboring states.