DEAD SEA

Salt deposits on the southwestern shore of the Dead Sea near Masada, Israel. Arabic Al-bahr Al-mayyit, Hebrew Yam Ha-melah (Salt Sea), landlocked salt lake between Israel and Jordan, the lowest body of water on Earth, which averages about 1,312 feet (400 m) below sea level. Its northern half belongs to Jordan; its southern half is divided between Jordan and Israel. After the 1967 Arab-Israeli War, however, the Israeli army remained in occupation of the entire western shore. The Dead Sea lies between the hills of Judaea to the west and the Transjordanian plateaus to the east. The Jordan River flows from the north into the Dead Sea, which is 50 miles (80 km) long and attains a width of 11 miles (18 km). Its surface area is about 394 square miles (1,020 square km). The peninsula of Al-Lisan (the tongue) divides the lake on its eastern side into two unequal basins; the northern basin encompasses about three-fourths of the lake's total surface area and reaches a depth of 1,300 feet (400 m); the southern basin is smaller and shallower (less than 10 feet on the average). During biblical times and up to the 8th century AD, only the area around the northern basin was inhabited, and the lake was about 115 feet (35 m) below its level of the late 20th century. It rose to its highest level (1,275 feet below sea level) in 1896 but receded again after 1935. The name Dead Sea can be traced back at least to the Hellenistic epoch (323 to 30 BC). It has been associated with biblical history since the time of Abraham (progenitor of the Hebrews) and the destruction of Sodom and Gomorrah (the two cities, according to the Old Testament, that were destroyed by fire from heaven because of their wickedness; the city sites are now possibly submerged in the southern part of the Dead Sea). The desolate rivers of the lake offered refuge to David (king of Israel) and later to Herod I the Great, king of Judaea, who at the time of the siege of Jerusalem by the Parthians in 40 BC barricaded himself in a fortress at Masada. Masada was the scene of a two-year siege that culminated in the mass suicide of its Jewish Zealot defenders and the occupation of the fortress by the Romans in AD 73. The Jewish sect that left the biblical manuscripts known as the Dead Sea Scrolls took shelter in caves to the northwest of the lake. The Dead Sea occupies the lowest part of the JordanDead Sea trench (350 miles long), which is a northern extension of the East African Rift Valley. It is a sunken block confined by two parallel geologic faults. The eastern fault, along the edge of the Moab Plateau, is more readily visible from the lake than is the western fault, which marks the gentler Judaean upfold. In the Jurassic and Cretaceous periods (208 to 66.4 million years ago), before the creation of the trench, an extended Mediterranean Sea covered Syria and Palestine. During the Miocene Epoch (23.7 to 5.3 million years ago), upheaval of the seabed produced the upfolded structures of the Transjordanian highlands and the central range of Palestine, causing the fractures that formed the Dead Sea depression. At that time, the Dead Sea was probably about the size that it is in modern times. During the Pleistocene Epoch (1,600,000 to 10,000 years ago), it rose to a height of about 700 feet (about 215 m) above its modern level, forming a vast inland sea that stretched some 200 miles (320 km) from the Huleh Valley area in the north to 40 miles (64 km) beyond its present southern limits. The Dead Sea did not spill over into the Gulf of Aqaba because it was blocked by a 100-foot rise in the highest part of Wadi Al-'Arabah, a seasonal watercourse that flows along an eastern extension of the central Negev highlands. About 2.5 million years ago or later, heavy stream flow into the lake deposited thick sediments of shale, clay, sandstone, rock salt, and gypsum. Later strata of clay, marl, soft chalk, and gypsum were dropped upon layers of sand and gravel. With the water evaporating faster than it was replenished by precipitation over the last 10,000 years, the lake gradually shrank to its present form. In so doing, it bared deposits that cover the Dead Sea valley to a thickness of 1 to 4 miles (1.6 to 6.4 km). The peninsula of Al-Lisan and Mount Sedom (historically Mount Sodom) are formations that resulted from movements of the Earth's crust. Mount Sedom's steep cliffs rise up from the southwestern shore. Al-Lisan is formed of strata of clay, marl, soft chalk, and gypsum interbedded with sand and gravel. Both Al-Lisan and beds made of similar material on the western side of the Dead Sea valley dip to the east. It is assumed that the uplifting of Mount Sedom and Al-Lisan formed a southern escarpment for the Dead Sea. Later, the sea broke through the western half of this escarpment to flood what is now the shallow southern end of the Dead Sea. The Dead Sea lies in a desert. Rainfall is scanty and irregular. Al-Lisan has about 2.5 inches (65 mm) of rain a year, and the town of Sedom (near historical Sodom) only about 2 inches. Owing to the lake's low elevation and sheltered location, winter temperatures are mild, averaging 63 F (17 C) in January at the southern end at Sedom and 58 F (14 C) at the northern end; freezing temperatures are unheard-of. Summer is very hot, averaging 93 F (34 C) in August at Sedom, with a recorded maximum of 124 F (51 C). Evaporation of the lake's watersestimated at about 55 inches (1,400 mm) a yearoften creates a thick mist above the lake. On the rivers the atmospheric humidity varies from 45 percent in May to 62 percent in October. Lake and land breezes, which are relatively common, blow off the lake in all directions in the daytime and then reverse direction to blow toward the centre of the lake at night. The inflow from the Jordan River, whose high waters occur in winter and spring, averages 19,000,000,000 cubic feet (540,000,000 cubic m) per year. Four modest but perennial streams descend from Jordan on the east through deep gorges: the Wadis Al-'Uzaymi, Zarqa' Ma'in, Al-Mawjib, and Al-Hasa. Down numerous other wadis, streams flow spasmodically and briefly from the neighbouring heights as well as from the depression of Wadi Al-'Arabah. Thermal sulfur springs also feed the rivers. Evaporation in summer and the intake of water, especially in winter and spring, cause seasonal variations in the level of the lake of from 12 to 24 inches (30 to 60 cm). The waters of the Dead Sea are extremely saline, and the concentration of salt increases toward the bottom. In effect, two different masses of water exist in the lake. Down to a depth of 130 feet (40 m), the temperature varies from 66 to 98 F (19 to 37 C), the salinity is slightly less than 300 parts per thousand, and the water is particularly rich in sulfates and in bicarbonates. After a zone of transition located between 130 and 330 feet (40 and 100 m), the lower waters have a uniform temperature of about 72 F (22 C) and a higher degree of salinity (approximately 332 parts per thousand); they contain hydrogen sulfide and strong concentrations of magnesium, potassium, chlorine, and bromine. The deep waters are saturated with sodium chloride, which is precipitated to the bottom. The lower waters are fossilized (i.e., being very salty and dense, they remain permanently on the bottom); the upper waters date from a few centuries after biblical times. The saline water has a high density. Bathers float on it easily. The fresh water of the Jordan stays on the surface; in the spring its muddy colour can be traced across the lake as far as 30 miles (50 km) south of the point where the river empties into the Dead Sea. The extreme salinity excludes any animal or vegetable life except bacteria. Fish carried in by the Jordan or by smaller streams when in flood die instantly. Apart from the vegetation along the rivers, the only plant life is discontinuous and consists mainly of halophytes (plants that grow in salty or alkaline soil). The Dead Sea constitutes an enormous salt reserve. In particular, salt deposits occur in the structures of Mount Sedom along the southwestern shore. The salt has been exploited on a small scale since antiquity. In 1929 a potash factory was opened near the mouth of the Jordan at Kaliya. Subsidiary installations were later built at Sedom. During the 194849 Arab-Israeli War, the factory at Kaliya was destroyed. A factory producing potash, magnesium, and calcium chloride was opened in Sedom in 1955. Another plant produces bromine and other chemical products. Because of its location on the contested Jordan-Israeli frontier, the Dead Sea has not been used to a great extent for navigation. Its shores are deserted, and permanent establishments are rare. Exceptions are the factory at Sedom, a few hotels and spas at Kaliya, and, in the west, a kibbutz (an Israeli agricultural community) in the region of the 'En Gedi oasis. Small cultivated plots are also occasionally found on the lakeshore. Additional reading Barbara Kreiger, Living Waters: Myth, History, and Politics of the Dead Sea (1988), explores the sea's natural history, political history, exploration, and use. Geologic information can be found in Leo Picard, Structure and Evolution of Palestine, with Comparative Notes on Neighbouring Countries (1943, reprinted 1959). David Neev and K.O. Emery, The Dead Sea: Depositional Processes and Environments of Evaporites (1967), analyzes the hydrology and climatology of the area.