Under the Dead Sea, Warnings on Climate and Earthquakes
An international team of scientists drilling deep under the bed of the Dead Sea has found evidence that the sea may have dried up during a past warm period analogous to scenarios for climate change in coming decades. With nations in the volatile region already running short on water, the finding could be a warning of worse shortages to come, they say. The lakebed cores, which contain about 200,000 years of environmental history–the Mideast’s longest archive–also record earthquakes and other natural phenomena, and may shed light on human development and current seismic risks. The preliminary results were presented today at a press conference at the American Geophysical Union’s fall meeting in San Francisco.
Spanning Israel, Jordan and Palestinian territory, the Dead Sea is the world’s lowest-lying place on land, with shores some 1,400 feet below sea level, and salty waters going down another 1,200 feet. Fed by the Jordan River drainage, it has shrunk rapidly over past decades, as Syria, Israel, Jordan and the Palestinian Authority pull water for farming and other uses.
Near the sea’s center, under 900 feet of water, the team penetrated some 750 feet of muddy sediment, then hit a layer of nearly pure pebbles, underlain by some 120 feet of salt. The salt suggests to them that the lake dried quickly, precipitating out solids. The pebbles appear to be a beach—given their position near the middle, a signal that the sea more or less disappeared. Research by others has already shown that the sea has fluctuated, but this is the first time anyone has found that it actually disappeared.
The cores have not yet been precisely dated, but the researchers have correlated some layers with isotopes found in Mideast cave deposits, and believe the total drying took place around 125,000 years ago—the height of a warm period between the two most recent ice ages, when the Mideast is already known to have been not only warmer, but drier, than today. Climate projections say that if the world keeps warming as it is now, the Mideast could return to this more arid state within decades.
“The Dead Sea’s level is already decreasing very quickly, because humans are using all of its fresh water sources,” said Steven L. Goldstein, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory and one of the project leaders. “The evidence it has actually dried down in the past without any human intervention means that its sources may stop running again, if forecasts of increasing aridity turn out to be correct.” Reports by the United Nations and others have cited water as a potential spark for future Mideast conflicts; in the past, the governments of Egypt and Jordan have said that they would never go to war against Israel—except over water.
The Dead Sea’s basin is formed by a moving tectonic boundary similar to California’s San Andreas fault, and the cores also contain a detailed log of past earthquakes there. When quakes occur, typically flat layers of sediment are twisted into convoluted shapes. With precise dating, these should form a history from ancient times to the present, and perhaps give a better picture of future risks the region may face.
“The 20th century has been very quiet for earthquakes, so people have stopped worrying about it,” said Zvi Ben-Avraham, a geoscientist at Tel-Aviv University, who is also leading the project. He points out that there are many earthquakes shown in the still largely unanalyzed cores, so the risk could be far greater than assumed. The last sizable one came in 1927, causing landslides that blocked the flow of the Jordan River for two days. This event, he pointed out, is strikinngly similar to an apparent stoppage of the Jordan prior to the Battle of Jericho, described in the Biblical book of Joshua. Some researchers have speculated that earthquakes may have been the cause of that city’s walls tumbling down, also described in the Bible, as well as events such as the destruction of Sodom and Gomorrah.
The drilling, some 10 years in the making, was done by investigators from Israel, the United States, Germany, Japan, Switzerland and Norway, under the auspices of the International Continental Scientific Drilling Program, which sponsored the project and covered much of the cost. The rest was funded by agencies and institute from participating countries, including the Israeli, German, Swiss and U.S. national science foundations.
In addition to Goldstein, the project leaders are Zvi ben Avraham of Tel-Aviv University, and Mordechai Stein of the Geological Survey of Israel. Others come from the GFZ German Research Center for Geosciences; Hebrew University of Jerusalem; Swiss Federal Institute of Technology in Zurich; International Research Center for Japanese Studies in Kyoto; and University of Minnesota. The team is hoping to involve scientists from Palestine and Jordan as well.