Photograph by Richard Nowitz, National Geographic
A cross-section of Dead Sea sediment. Crumpled areas represent earthquakes. Photograph courtesy Adi Torfstein.
Published December 8, 2011
Sediment cores from the Dead Sea (map) reveal that the water body may once have completely dried up, researchers say. The discovery raises fears the sea could vanish again.
The salty sea—actually a lake—whose surface now lies more than 1,380 feet (420 meters) below sea level, is not only the lowest nonmarine place on Earth but also the catch basin for water flowing from much of Jordan, Israel, Syria, Lebanon, and Palestine.
As such, "it is the most fantastic recorder for past climate," geophysicist Zvi Ben-Avraham said this week at a meeting of the American Geophysical Union in San Francisco.
Drilling cores collected in 2010 revealed clear annual layers, almost like tree rings, said geologist Steven Goldstein of Columbia University's Lamont-Doherty Earth Observatory.
White layers in the cores represent summer dry periods, when the lake slowly evaporated and calcium carbonate settled to the bottom. Dark layers are mud and silt from winter storms.
"We can use these to reconstruct the climate on a seasonal basis," Goldstein said.
In fact, he noted, the drilling team was able to watch a new dark layer being formed, as a flash flood dumped sediment out of the Israeli hills, turning the waters a muddy brown.
(Read about the Dead Sea's "dramatic decline" as a travel destination.)
Dead Sea Bible Links?
The team also found "jumbled" sections in the Dead Sea sediment, where normally rhythmic layers had been stirred together by large earthquakes, Goldstein said.
Because the cores weren't ready for study until last month, he said, scientists haven't had time to count the number of earthquakes, let alone date them.
"What I can tell you," he said, "is that there are a lot of earthquake deposits throughout the core," which stretches back about 200,000 years.
Ben-Avraham, head of the Minerva Dead Sea Research Center at Tel Aviv University in Israel, noted that this is important because, when it comes to earthquakes, the last century in the Middle East was unusually quiet.
"People don't take this into consideration," Ben-Avraham said, "but we have mighty earthquakes."
Looking farther back, one of the seismically active eras revealed by the core samples appears to have been about 4,000 years ago, he said.
"If you believe the biblical chronology, this is roughly [the time of] Sodom and Gomorrah," he said. During this period, according to the Book of Genesis, God "rained fire and brimstone from heaven, and destroyed all."
(Find out about the King James Bible in National Geographic magazine.)
A later text, Antiquities of the Jews, tells of an earthquake in Judea, an ancient land bordering the Dead Sea—"such a one as had not happened at any other time, and which earthquake brought a great destruction upon the cattle in that country. About ten thousand men also perished by the fall of houses. ... "
The cores also show layers of salt. These, Columbia's Goldstein said, represent eras when the climate dried and the Dead Sea evaporated and shrank.
Some of these occurred during the biblical period, Goldstein added, noting that the dry spells are interspersed with wet intervals.
"So we see lean years and the fat years like those described in the ancient texts," he said.
The Dried Sea
Even more severe droughts occurred much longer ago, accompanied by salt deposits up to 150 feet (45 meters) thick, researchers said at the meeting.
In the worst such instance, about 120,000 years ago, Goldstein said, there is even a layer of pebbles akin to current Dead Sea beach deposits, suggesting that at this time the entire lakebed was dry—and that it could happen again.
Irrigation and drinking-water diversions have been cutting off the flow of water to the Dead Sea, raising concerns for its future, said Emi Ito, a lake researcher from the University of Minnesota and a member of the study team.
Prior models, she said, had indicated that while the Dead Sea might shrink dramatically, a remnant would remain.
But we now have evidence that the lake once dried completely even without the humans diverting its water sources, "so all of those previous models may have to be reconsidered," she said.
Tel Aviv University's Ben-Avraham added, "The message that comes out from these drill holes [is] that what we see happening in the Middle East mimics a severe dry period" depicted in the geologic record.
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