The Dead Sea is a sea located in the Dead Sea Rift, which is part of a long fissure in the Earth’s surface called the Great Rift Valley. The 6,000 km (3,700 mile) long Great Rift Valley extends from the Taurus Mountains of Turkey to the Zambezi Valley in southern Africa. The Great Rift Valley formed in Miocene times as a result of the Arabian Plate moving northward and then eastward away from the African Plate.
Around three million years ago what is now the valley of the Jordan River, Dead Sea, and Wadi Arabah was repeatedly inundated by waters from the Red Sea. The waters formed in a narrow, crooked bay which was connected to the sea through what is now the Jezreel Valley. The floods of the valley came and went depending on long scale climatic change. The lake that occupied the Dead Sea Rift, named "Lake Sodom", deposited beds of salt, eventually coming to be 3 km (2 miles) thick.
According to geological theory, approximately two million years ago the land between the Rift Valley and the Mediterranean Sea rose to such an extent that the ocean could no longer flood the area. Thus, the long bay became a lake.
The first such prehistoric lake is named "Lake Gomorrah." Lake Gomorrah was a freshwater or brackish lake that extended at least 80 km (50 miles) south of the current southern end of the Dead Sea and 100 km (60 mi) north, well above the present Hula Depression. As the climate turned more arid, Lake Gomorrah shrank and became saltier. The large, saltwater predecessor of the Dead Sea is called "Lake Lisan."
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Near Ein Gedi, salt builds up along the shores of the Dead Sea.
In prehistoric times great amounts of sediment collected on the floor of Lake Gomorrah. The sediment was heavier than the salt deposits and squeezed the salt deposits upwards into what are now the Lisan Peninsula and Mount Sedom (on the southwest side of the lake). Geologists explain the effect in terms of a bucket of mud into which a large flat stone is placed, forcing the mud to creep up the sides of the pail. When the floor of the Dead Sea dropped further due to tectonic forces the salt mounts of Lisan and Mount Sedom stayed in place as high cliffs. (see salt domes)
From 70,000 to 12,000 years ago the lake level was 100 m (328 ft) to 250 m (820 ft) higher than its current level. This lake, called "Lake Lisan", fluctuated dramatically, rising to its highest level around 26,000 years ago, indicating very wet climate in the Near East. Sometime around 10,000 years ago the lake level dropped dramatically, probably to levels even lower than today. During the last several thousand years the lake has fluctuated approximately 400 m (1,310 ft) with some significant drops and rises. Current theories as to the cause of this dramatic drop in levels rule out volcanic activity, therefore it may have been a seismic event.
The Jordan River is the only major water source flowing into the Dead Sea. There are no outlet streams.
The northern part of the Dead Sea receives scarcely 100 mm (4 in) of rain a year. The southern section barely 50 mm (2 in). The Dead Sea zone’s aridity is due to the rainshadow effect of the Judean Hills. The highlands east of the Dead Sea receive more rainfall than the Dead Sea itself.
The mountains of the western side, the Judean Hills, rise less steeply from the Dead Sea than do the mountains of the eastern side. The mountains of the eastern side are also much higher. Along the southwestern side of the lake is a 210 m (700 ft) tall halite formation called "Mount Sedom".
[edit] Climatic features and therapies
The Dead Sea’s climate offers year-round sunny skies and dry air with low pollution. It has less than 50 millimetres (2.0 in) mean annual rainfall and a summer average temperature between 32 and 39 °C (90-102°F). Winter average temperatures range between 20 and 23 °C (68-74°F). The region has weakened ultraviolet radiation, particularly the UVB (erythrogenic rays), and an atmosphere characterized by a high oxygen content due to the high barometric pressure. The shore is the lowest dry place in the world.[6] Proximity to the sea affects temperatures nearby because of the moderating effect a large body of water has on climate. During the winter months, sea temperatures tend to be higher than land temperatures, and vice versa during the summer months. This is the outcome of slow penetration of the sun’s rays into the sea, which is a
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A tourist demonstrates the unusual buoyancy caused by high salinity.
Until the winter of 1978-1979, the Dead Sea was composed of two stratified layers of water that differed in temperature, density, age, and salinity. The topmost 35 metres (115 ft) or so of the Dead Sea had a salinity that ranged between 300 and 400 parts per thousand and a temperature that swung between 19 °C (66 °F) and 37 °C (98 °F). Underneath a zone of transition, the lowest level of the Dead Sea had waters of a consistent 22 °C (72 °F) temperature and complete saturation of sodium chloride (NaCl).[citations needed] Since the water near the bottom is saturated, the salt precipitates out of solution onto the sea floor.
Beginning in the 1960s water inflow to the Dead Sea from the Jordan River was reduced as a result of large-scale irrigation and generally low rainfall. By 1975 the upper water layer of the Dead Sea was actually saltier than the lower layer. The upper layer nevertheless remained suspended above the lower layer because its waters were warmer and thus less dense. When the upper layer finally cooled down so that its density was greater than the lower layer the waters of the Dead Sea mixed. For the first time in centuries the lake was a homogeneous body of water. Since then stratification has begun to redevelop.[7]
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Many people believe the mud of the Dead Sea has special healing and cosmetic uses.
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A rough Dead Sea, with salt deposits on cliffs.
The mineral content of the Dead Sea is significantly different from that of ocean water. The exact composition of the Dead Sea water varies with season, depth, temperature and so on. The concentration of ionic species (in g/kg) of Dead Sea surface water in the early 1980s was found to be: Cl− (181.4), Br− (4.2), SO42− (0.4), HCO3− (0.2), Ca2+ (14.1), Na+ (32.5), K+ (6.2) and Mg2+ (35.2). The total salinity was 276 g/kg.[8] These results show that w/w% composition of the salt, as anhydrous chlorides, was calcium chloride (CaCl2) 14.4%, potassium chloride (KCl) 4.4%, magnesium chloride (MgCl2) 50.8% and sodium chloride (common salt, NaCl) 30.4%. In comparison, the salt in the water of most oceans and seas is approximately 97% sodium chloride. The concentration of sulfate, SO42−, ions is very low, and the bromide ion, Br− concentration is the highest of all waters on Earth.
Comparison between the chemical composition of the Dead Sea to other lakes and oceans show that the salt concentration in the Dead Sea is 31.5% (the salinity fluctuates somewhat). The unusually high concentration of salt results in a similarly high density of up to 1.24 kg/L, depending on temperature and salinity. Anyone can easily float in the Dead Sea because of natural buoyancy. In this aspect, the Dead Sea is similar to the Great Salt Lake in Utah, in the United States.
One of the most unusual properties of the Dead Sea is its discharge of asphalt. From deep seeps, the Dead Sea constantly spits up small pebbles of the black substance. After earthquakes, chunks as large as houses have been found.
The Dead Sea area has become a major center for health research and treatment for several reasons. The mineral content of the waters, the very low content of pollens and other allergens in the atmosphere, the reduced ultraviolet component of solar radiation, and the higher atmospheric pressure at this great depth each have specific health effects. For example, persons suffering reduced respiratory function from diseases such as cystic fibrosis seem to benefit from the increased atmospheric pressure.[9]
Sufferers of the skin disorder psoriasis also benefit from the ability to sunbathe for long periods in the area due to its position below sea level and subsequent result that many of the sun’s harmful UV rays are reduced. Furthermore, Dead Sea salt has been found to be beneficial to psoriasis patients.[10]
[edit] Flora and fauna
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Dead Sea in the morning, seen from Masada
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World’s lowest (dry) point, Jordan 1971
[edit] In Judaism
The human history of the Dead Sea goes all the way back to remote antiquity. Just north of the Dead Sea is Jericho. Somewhere, perhaps on the Dead Sea’s southeast shore, would be the cities mentioned in the Book of Genesis which were said to have been destroyed in the times of Abraham: Sodom and Gomorra (Genesis 18) and the three other "Cities of the Plain" - Admah, Zeboim and Zoar (Deuteronomy 29:23). King David was said to have hidden from Saul at Ein Gedi nearby.
Essenes had settled on the Dead Sea’s western shore; Pliny the Elder identifies their location with the words, "on the west side of the Dead Sea, away from the coast … [above] the town of Engeda" (Natural History, Bk 5.73); and it is therefore a hugely popular though not uncontested hypothesis today, that same Essenes are identical with the settlers at Qumran and that "the Dead Sea Scrolls" discovered during the 20th century in the nearby caves had been their own library.
[edit] In Christianity
The remoteness of the region attracted Greek Orthodox monks since the Byzantine era. Their monasteries such as Saint George in Wadi Kelt and Mar Saba in the Judean Desert are places of pilgrimage.
Mount Sedom, on the southwest side of the lake, is a giant mountain of halite.
[edit] In Islam
In Islamic explorers and scientists arrived to analyze the minerals and conduct research into the unique climate. Tourism in the region has been developed since the 1960s.
[edit] Recent History
The Dead Sea Scrolls were found in caves at Qumran at the Dead Sea. The world’s lowest road, Highway 90, runs along the Israeli and West Bank shores of the Dead Sea at 393 m (1,289 ft) below sea level.
Besides the unique water of the Dead Sea itself, there are also health spas and hot springs along the shore. While a golf course named for Sodom and Gomorrah was built by the British at Kalia on the northern shore, the first major hotels were built in Israel, first at nearby Arad, and since the 1960s at the Neve Zohar resort complex. The Jordanian side has seen increasing development in recent years, and it also includes international franchises.
[edit] Industry
turbulent times. The company quickly grew into the largest industrial site in the Middle East
[citation needed] and in 1934 built a second plant on the southwest shore, in the
Mount Sodom area, south of the
‘Lashon’ region of the Dead Sea. Palestine Potash Company supplied half of Britain’s potash during
World War II, but ultimately became a casualty of the
1948 Arab-Israeli War. Its remnants were nationalised and
Dead
[edit] Recession
In recent decades, the Dead Sea has been rapidly shrinking because of diversion of incoming water. From an elevation of 395 m (1,296 ft) below sea level in 1970 [13] it fell 22 m (72 ft) to 418 m (1,371 ft) below sea level in 2006, reaching a drop rate of 1 m (3 ft) per year. Although the Dead Sea may never entirely disappear,[citation needed] because evaporation slows down as surface area decreases and salinity increases, it is feared that the Dead Sea may substantially change its characteristics.
The Dead Sea level drop has been followed by a groundwater level drop, causing brines that used to occupy underground layers near the shoreline to be flushed out by freshwater. This is believed to be the cause of the recent appearance of large sinkholes along the western shore – incoming freshwater dissolves salt layers, rapidly creating subsurface cavities that subsequently collapse to form these sinkholes.[14]
One of the plans which were suggested as a means to stop the recession of the Dead negative impacts of the project on the natural environment of the Dead Sea and Arava.
In 2007, the level of the Dead Sea fell by 1 metre.[15]
[edit] Gallery
Israeli highway beside the Dead Sea
Dead Sea at Dusk (from Suwayma, Jordan)
Sinkholes at Mineral Beach
[edit] See also
[edit] Further reading
- Yehouda Enzel, et al, eds (2006) New Frontiers in Dead Sea Paleoenvironmental Research, Geological Society of America, ISBN
[edit] External links
The Dead Sea is a sea located in the Dead Sea Rift, which is part of a long fissure in the Earth’s surface called the Great Rift Valley. The 6,000 km (3,700 mile) long Great Rift Valley extends from the Taurus Mountains of Turkey to the Zambezi Valley in southern Africa. The Great Rift Valley formed in Miocene times as a result of the Arabian Plate moving northward and then eastward away from the African Plate.
Around three million years ago what is now the valley of the Jordan River, Dead Sea, and Wadi Arabah was repeatedly inundated by waters from the Red Sea. The waters formed in a narrow, crooked bay which was connected to the sea through what is now the Jezreel Valley. The floods of the valley came and went depending on long scale climatic change. The lake that occupied the Dead Sea Rift, named "Lake Sodom", deposited beds of salt, eventually coming to be 3 km (2 miles) thick.
According to geological theory, approximately two million years ago the land between the Rift Valley and the Mediterranean Sea rose to such an extent that the ocean could no longer flood the area. Thus, the long bay became a lake.
The first such prehistoric lake is named "Lake Gomorrah." Lake Gomorrah was a freshwater or brackish lake that extended at least 80 km (50 miles) south of the current southern end of the Dead Sea and 100 km (60 mi) north, well above the present Hula Depression. As the climate turned more arid, Lake Gomorrah shrank and became saltier. The large, saltwater predecessor of the Dead Sea is called "Lake Lisan."
In prehistoric times great amounts of sediment collected on the floor of Lake Gomorrah. The sediment was heavier than the salt deposits and squeezed the salt deposits upwards into what are now the Lisan Peninsula and Mount Sedom (on the southwest side of the lake). Geologists explain the effect in terms of a bucket of mud into which a large flat stone is placed, forcing the mud to creep up the sides of the pail. When the floor of the Dead Sea dropped further due to tectonic forces the salt mounts of Lisan and Mount Sedom stayed in place as high cliffs. (see salt domes)
From 70,000 to 12,000 years ago the lake level was 100 m (328 ft) to 250 m (820 ft) higher than its current level. This lake, called "Lake Lisan", fluctuated dramatically, rising to its highest level around 26,000 years ago, indicating very wet climate in the Near East. Sometime around 10,000 years ago the lake level dropped dramatically, probably to levels even lower than today. During the last several thousand years the lake has fluctuated approximately 400 m (1,310 ft) with some significant drops and rises. Current theories as to the cause of this dramatic drop in levels rule out volcanic activity, therefore it may have been a seismic event.
The Jordan River is the only major water source flowing into the Dead Sea. There are no outlet streams.
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