The Life of the Dead Sea

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Millions of years ago, seismic forces where two tectonic plates come together formed the Great Rift Valley. Millions of years later, the Dead Sea was created in that valley—the lowest point on earth. Thus begins the story of the life of the Dead Sea. That life is now imperiled. Can the Dead Sea be saved?

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Between 70,000 and 14,000 years ago (the Pleistocene epoch in geologic time), a large body of water we call Lake Lisan filled the valley that extends from the Sea of Galilee to the Dead Sea and beyond it to the south. At its maximum, the level of Lake Lisan was about 800 feet (about 250 m) higher than the current level of the Dead Sea. Then, between 14,000 and 12,000 years ago, when the ice sheets in North America and Europe retreated, the melting of the glaciers caused a shift in the regional weather patterns. This climate change diminished the rainfall in Lake Lisan’s watershed, and it shrank. Some say it dried up.¹ When the rains returned about 10,000 years ago, water levels rose again and a new lake—the Dead Sea—was born.²

Millions of years before Lake Lisan and the Dead Sea were formed, the valley in which the sea lies was created when the once-continuous Arabo-African continent pulled apart, forming the Red Sea. The Arabian tectonic plate then broke further along the Dead Sea fault line (a series of deep fractures that cut through the earth’s crust) that separates Sinai and the Levant from Jordan and the Arabian interior. These two plates are still sliding past each other; the Arabian plate on the eastern side is moving north, and the Sinai plate on the western side is moving south. Massive tectonic forces caused the Great Rift Valley in which the Dead Sea is located to sink down. These same tectonic forces uplifted the mountains on either side of the valley.

The fault motion on this tectonic boundary has resulted in numerous earthquakes that have periodically rocked the region. The Jewish historian Josephus describes an earthquake in 31 B.C.E., which created the cracks that are still visible at one of the stepped mikva’ot (ritual baths) at Qumran, near where the Dead Sea Scrolls were found.

The Dead Sea is the lowest continental depression on the face of the earth. Its surface is now 1,380 feet (420 m) below sea level. This extreme negative elevation, in combination with the tectonically elevated mountains that flank the basin, promotes an extremely arid environment. The Dead Sea receives almost no direct precipitation. (The annual precipitation is about 100 mm—less than 4 inches.³) Summer air temperatures reach over 104 degrees Fahrenheit (40° C). Surface soil temperatures rise even higher.

Water that enters the Dead Sea has no outlet. Hence, in many ways it is a flexible lake—expanding and contracting with the amount of water that 037enters it. When the amount of rainfall in the watershed from which it derives its water increases, then the Dead Sea level rises. Conversely, during periods of reduced rainfall in the watershed area, the Dead Sea level falls. And, of course, the shoreline moves inland in wetter times and retreats in drier times. The principal Dead Sea watershed area is located in the mountains north of the upper Jordan River, which flows into the Sea of Galilee and subsequently south into the Dead Sea via the lower Jordan River.⁴

Geologists have been able to chart fluctuations in the level of the Dead Sea using sediment and geomorphic indicators of past shorelines,⁵ as well as the elevations of archaeological sites on the Dead Sea shores.⁶ Historical photographs and accounts from Victorian-era travelers to the Holy Land, including Mark Twain, have helped establish that Dead Sea levels were rising throughout the 19th century. Between the 14th and 19th centuries (a period known as the “Little Ice Age” in Europe, when Alpine glaciers advanced), levels of the Dead Sea were low. The previous period, during the Crusades and the Medieval Age (mid-11th–13th centuries), was a warm climatic period, so Dead Sea levels were once again high. Further back in time, it becomes more difficult to reconstruct the level of the sea. It does appear, however, that in four archaeological periods—the Byzantine period (late fourth–sixth centuries C.E.), the Late Hellenistic to Roman period (first century B.C.E.–first century C.E.), the Late Chalcolithic to Middle Bronze Age (3450–1550 B.C.E.) and the Pre-pottery Neolithic period (8500–5500 B.C.E)—the level of the Dead Sea was high.

As the lake’s level has fluctuated, so has habitation on the shore of the Dead Sea. Episodic waves of settlement and abandonment characterize the areas adjacent to the sea. For example, at the Biblical site of Heshbon on the plateau east of the Dead Sea, the number of settlements increased when the lake was high, and was lower when the lake was low.⁷

The Iron Age (the Biblical period, 1200–586 B.C.E.), however, appears to be somewhat of an exception to this trend. Sites with Iron Age occupation are well documented around the Dead Sea, even during a period when the water line was low. But the archaeological remains that have been found from that period are largely the remnants of towers built in the eighth and seventh centuries B.C.E., perhaps to protect the eastern frontier from 038Assyrian or, later, Babylonian attack. Most of these Iron Age towers (Mezad Mazal, Mezad Gozaland Qumran) and a fort (Ein Gedi) were reoccupied during the Late Hellenistic and Hasmonean periods (third–first centuries C.E.), suggesting that these locations had high strategic or resource value.

Some of the most prominent archaeological sites that line the western shore of the Dead Sea date from the Hasmonean and Herodian periods (141 B.C.E.–70 C.E.).⁸ Carbon and oxygen isotopic analyses of wood within the Roman siege ramp at Masada apparently provide evidence of a moister climate in this period.⁹ Jericho, Qumran, Masada and other sites in the area (Ein Feshkha, Turabeh, Ein Gedi, ‘En Bokek and ‘En Tamar) flourished around springs in the first century C.E.

Elaborate water delivery and storage systems, including long aqueducts and covered cisterns, were also built to use ephemeral stream flow and rainwater catchment basins. This region was near the eastern front of the Judean kingdom, and water 039systems were evidently constructed here both for defensive purposes and for cultivation of crops, including balsam. These trees produced a valuable resin used in the perfume industry referred to in ancient historical accounts. South of ‘En Bokek lay the border between Judea and the Nabataeans, who dominated the overland incense and spice route through Petra, south of the sea and east of the Rift Valley.¹⁰

Plantations around the Dead Sea also grew date palms on relatively large tracts of land. Jericho is called the “city of palms” in Deuteronomy 34:3. The fruit of the tree could be eaten or made into date honey or date wine.

And of course salt, which was an important dietary staple used in the preparation and preservation of foods, was abundant. In Hebrew, the Dead Sea is known as Yam ha-Melech (“the Sea of Salt”) (Genesis 14:3; Deuteronomy 3:17; Joshua 3:16). More than 30 percent of the water in the Dead Sea is made of various salts. This is the highest salinity of any body of water on earth. 041Nevertheless, the sea is not completely dead. It is home to some microorganisms—highly specialized green algae and red bacteria—that can endure the sea’s hyper-saline brines.¹¹

On the northeastern shore of the Dead Sea lay the hot springs of Callirhoë, where Herod the Great came to find relief from his suffering before he died.^a Farther south along the eastern shore lies Qazone, with its 3,500-grave cemetery (largely of the Roman-Nabataean period), adjacent to the town of Mazra’a.^b Recent excavations at Qazone have yielded, in addition to pottery, fine examples of textiles, leather and even a mummified body.¹² The extreme aridity of the Dead Sea region has defied the decay process and allowed artifacts from this and other sites around the Dead Sea to remain exquisitely preserved.

In this period, boat docks were constructed on the Dead Sea shores at a lake elevation 80 feet (25 m) higher than it stands today, again demonstrating the existence of a wetter period. The dock located at Khirbet Mazin on the west connected boat travelers with the hot springs and medicinal pools at the Callirhoë dock on the east. A dock at Rujm el-Bahr on the north indicates probable anchorages in Ein Gedi and Masada on the southwest.¹³

At least one of these docks had dry-dock facilities to protect the boats and to clean them from the Dead Sea’s alkaline brine.¹⁴ Even today the research vessel we geologists use for marine geophysical studies and boats used in the potash industry experience rapid corrosion and must be fastidiously cleaned and stored out of the water.

The Dead Sea has been called by several different names. As noted earlier, in Hebrew it is known as the Salt Sea. In Latin, it is called Lacus Asphaltitis (“Asphalt” or “Pitch Lake”). In antiquity, bitumen (asphalt or pitch) was used as a sealant for waterproofing, as well as for medicinal and agricultural purposes. It was also traded to Egypt for use in the embalming process.¹⁵

Greeks and Romans referred to the Dead Sea as the Asphalt Lake because blocks of bitumen floated on the water and were apparently harvested. The 043last occurrence of such blocks was in the 1950s, when a huge block, as tall as a man and twice as wide, floated ashore.¹⁶ Similar stories of large blocks weighing over a ton are recorded. Smaller blocks were harvested in boats. These blocks are apparently produced when seismic shifting of the faults below the Dead Sea loosen and provide conduits for the heavy oil to be liberated from the deeper reservoirs. The appearance and disappearance of floating bitumen may be related to earthquake cycles in which periods of increased seismic activity are followed by periods of earthquake quiescence. Reflecting the seismic activity of the first century B.C.E., Josephus tells us that the sea “in many places casts up black masses of asphalt, which float on the surface, in their shape and size resembling decapitated bulls.”¹⁷

Liquid asphalt sometimes seeps through planes that bound the Dead Sea basin. These seeps may be the “slime pits” mentioned in the King James translation that the kings of Sodom and Gomorrah fell into when they tried to flee from battle (Genesis 14:10). Modern translations call them “bitumen pits,” rather than “slime pits.” The Hebrew word is hemar, which means asphalt.

This asphalt seepage, which is simply heavy hydrocarbon, naturally raises the question of whether there are significant oil reserves under the Dead Sea or in the vicinity. Several years ago, in Nahal Hemar (Asphalt Valley), I actually saw thick droplets of oil dripping out along the fault contact between the marl and the limestone bedrock—a tantalizing hint at the potential of hydrocarbon resources that lie far below.

It has been estimated (conservatively, it is said) that the Dead Sea basin holds between eight and ten billion barrels of oil.¹⁸ Since 1953 a number of exploration wells have been sunk, but no commercially viable source has been discovered. The giant reservoirs and oil fields that characterize much of the Middle East continue to elude Israeli and Jordanian attempts at lucrative petroleum exploitation. But the search for oil in the Dead Sea basin is still in its relatively early stages.

The cliffs of bare limestone that line the western shore and the sandstone and other rocks that line the eastern escarpment of the Dead Sea are pocked with natural caves. Most of the caves were formed by slow dissolution of the minerals in the limestone bedrock that itself formed back in the age of the dinosaurs. These caves typify a region that is rugged, mountainous and remote. The caves were often used in antiquity for refuge. David hid 044from King Saul in a cave in Ein Gedi (1 Samuel 24:1–3). Rebels hiding from the Roman legions in the First Jewish Revolt (66–73 C.E.) and the Second Jewish Revolt (or Bar-Kokhba Revolt, 132–135 C.E.) also fled to these caves. Dead Sea Scrolls and other manuscripts were hidden in these caves.

The most famous cave east of the Dead Sea is Lot’s Cave, located in the mountains above Safi, where a Byzantine monastery was located (see In Depth: Jordan’s New Dead Sea Museum).^c Across the valley from Lot’s Cave (on the western side of the lake) is the rock salt formation known as Mount Sedom with caves of extraordinary beauty.

Caves were also hand-dug into the naturally soft lime mud (marl) and silty clay that were deposited on the floor of Lake Lisan in the Pleistocene epoch. In several of these marl caves near Qumran, thousands of fragments of Dead Sea Scrolls were found. Similar caves, but none containing scrolls, are located north of the Dead Sea at al-Maghtas. This is where John the Baptist preached and where he baptized Jesus at “Bethany on the other side of the Jordan” (John 1:28).^d Byzantine monks also dug caves in the hermitages of Dayr Al-Qattar Al-Byzanti on the Lisan Peninsula¹⁹ and the Chapel of the Crosses at En Tamar, southwest of the Dead Sea.²⁰

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The major difference between the western and eastern sides of the Dead Sea is the height of the plateau that towers above the valley; the eastern side is much higher. On the western side, the drop from the plateau of the Judean desert to the shore of the Dead Sea varies between 1,000 and 1,600 feet (300–500 m). On the eastern side, however, the drop from the plateau of Moab to the seashore can be over 3,000 feet (900 m) in places. South of the Dead Sea, the drop from the plateau to the dry valley (the Aravah) is well over 5,000 feet (1,500 m). The wadis or drainages on the eastern side—Wadi Zerka Main, Wadi Mujib and Wadi Hasa—are also larger, commensurate with the higher elevation from which they begin and from their increased watershed size. The majestic views in this area are simply spectacular and constitute one of Jordan’s newest tourist attractions: the Dead Sea panorama park and museum (see In Depth: Jordan’s New Dead Sea Museum).

The rising and retreating level of the lake in response to slight changes in climate also affects the shape of the lake. A satellite view of the Dead 046Sea a few decades ago shows a long, narrow lake that is separated into two basins by a peninsula that extends into the lake from the east. The Lisan Peninsula (lisan means “tongue” in Arabic) has a cape or bay on the north and a smaller one on the south. The northern one is named for the English naval officer Lieutenant T.H. Molyneux, who explored the sea in the mid-19th century; the southern one is named for the Irish explorer Christopher Costigan, who worked here a few years earlier. They were followed in 1848 by Lieutenant William F. Lynch, who, on behalf of the U.S. Navy, conducted the most important pre-modern study of the lake.^e The strait between the northern and southern basins of the lake is named for Lynch.

When the Dead Sea level was high, most of the eastern shore was impassable due to the sheer cliffs that drop down precipitously to the water’s edge. The western shoreline, on the other hand, weaves in and out as large alluvial fans from the drainages that originate high in the Judean mountains deliver sediment that has built a plain at the base of the western escarpment. As we shall see, however, recent changes in the lake level have made passage easier.

Today the lake lies at 1,380 feet (420 m) below mean sea level. The rate of fall of the lake level has accelerated in the last decade, reaching more than 3 feet (1 m) per year. The northern basin of the Dead Sea is quite deep. The bottom lies about 1,000 feet (300 m) below the current surface of the lake. But the level of the shallow southern basin has dropped so low that it is now disconnected from the northern basin and is occupied only by industrial ponds.

Perhaps the one happy advantage of the present low level of the lake is that roads can now run north and south on both sides of the lake. This is a fairly new addition on the Jordanian side, where the road was opened only about a decade ago. On the Israeli side, the road at the base of the steep cliffs of Ras Feshkha south of the spring of Ein Feshkha would be submerged if the Dead Sea level rose more than 80 feet (25 m). In the past 50 years, the Dead Sea has lowered about that much.

Water is pumped into the now-dry southern basin to fill evaporation ponds for the potash industry: the Dead Sea Works (Israel) and the 049Arab Potash Company (Jordan). Potassium chloride (potash) used for fertilizer is the main extraction produced through evaporation of Dead Sea water. Magnesium, bromine and other chemicals and salts are also extracted from the Dead Sea water and exported to the global market. The cosmetic industry also markets a wide range of therapeutic products derived from the sea.

Although the mineral industry is healthy, the tourist industry is struggling to cope with rapidly falling Dead Sea levels. Dead Sea bathing sites like Ein Feshkha and Ein Gedi that had facilities at the beach 20 years ago now find their shower houses stranded a kilometer or more from the water line. Carts must ferry bathers to their destination. But people still come, as did the Romans before them, to be healed by the unique elixir of the Dead Sea water and to bob unsinkable in the brine, even though the water feels greasy and tastes bitter. As the Web site of the Israeli Ministry of Foreign Affairs puts it: “Not only are [Dead Sea] waters unique, but so is the very atmosphere above it. There is an atmospheric pressure high enough to filter the sun’s harmful UV rays, more oxygen than at sea level, and more calming bromine in the air around the Dead Sea than anywhere else on earth.”

The retreat of the Dead Sea shoreline due to the low lake level has exacerbated a new and catastrophic environmental problem. As fresh groundwater flows down to an ever-lower sea level, it flushes and dissolves a buried layer of halite salt near the shores. When the lake was higher, this salt layer was relatively stable because freshwater draining to the sea came in at a higher elevation, above the salt layer. As the lake level has dropped, however, freshwater flow in the ground now flushes through the buried salt layer, dissolving it on its path to the sea. Without the salt layer, the result is a series of extremely dangerous sinkholes. The collapse is sudden and can be catastrophic (see In Depth: Rescue Squad Organizer Falls 30 Feet into Sinkhole). The problem is concentrated on the western margin in Israel and east of the Lisan Peninsula in Jordan. Large, gaping pits that drop down as much as 65 feet (20 m) have been opening since the mid-1980s, and the formation of the sinkholes has accelerated since 2000.²¹ These sinkholes are having a devastating effect on the infrastructure around the Dead Sea, especially on the agricultural fields in Jordan. The problem shows no signs of going away.

The source of the problem, of course, is that the Dead Sea is not getting a sufficient inflow of fresh water to replace the water that evaporates. The lower Jordan River, south of the Sea of Galilee (the Kinneret, in Hebrew), which traditionally is the major source of inflow, now carries only a trickle of water. Water is a valuable commodity in the Middle East, not to be wasted in the brine of the Dead Sea, so canals have been constructed by neighboring countries to divert water from the Sea of Galilee and its tributaries. Drainage areas around the Dead Sea and to the south deliver water to the basin only during flash floods, except for the perennial flow of the Wadi Hasa and Wadi Mujib in Jordan. The new dam on the Wadi Mujib now captures this major inflow and thus starves even more water from the lake.

It is clear that the Dead Sea levels will continue to fall rapidly as the sweet water flowing into it is used to feed the growing demand of a growing population. However, geochemical analyses provide an estimate on how much lower the Dead Sea can fall. Limits of evaporation due to increased water density indicate that the level of the Dead Sea may not be able to drop below 1,670 to 1,740 feet (510–530 m) below sea level, which should put a stop to the lowering in about another 300 feet (100 m).²² Such as it is, that’s the good news.