Dead Sea
The
Dead Sea (; ) is both the
lowest point on Earth at 418 meters (1,371 ft) below
sea level and falling
[Monitoring of the Dead Sea. Israel Marine Data Center (ISRAMAR).], and the deepest
hypersaline lake in the world at 330 meters (1,083 ft) deep and 799 meters (2,621 ft) below sea level. It is also one of the saltiest bodies of water on Earth with a
salinity of about 300
ppt, This is about 8.6 times greater than the average ocean salinity. It measures 67 kilometers (42 mi) long, up to 18 kilometers (11 mi) wide, and is located on the border between the
West Bank,
Israel, and
Jordan, and lies in the
Jordan Rift Valley. The main
tributary is the
Jordan River.
The Dead Sea has attracted interest and visitors from around the Mediterranean basin for thousands of years. It was a place of refuge for
King David, it was one of the world's first health resorts for
Herod the Great, and it has been the supplier of products as diverse as balms for Egyptian
mummification to
potash for fertilizers.
In Hebrew the Dead Sea is called the
- meaning "sea of
salt", or
Yam ha-Mavet - meaning "sea of death". In past times it was the "Eastern Sea" or the "Sea of Arava". In
Arabic the Dead Sea is called meaning "the Dead Sea", or less commonly
Bahr Lūţ meaning "the Sea of
Lot". Historically, another Arabic name was the "Sea of Zoar", after a nearby town. To the Greeks, the Dead Sea was "Lake
Asphaltites" (see below).
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Satellite photograph showing the location of the Dead Sea |
The Dead Sea is located in the
Dead Sea Rift, which is part of a long
fissure in the Earth's surface called the
Great Rift Valley. The 6000 km (3700 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/Nahal Arava was repeatedly inundated by waters from the
Mediterranean 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 long 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 miles) 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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Mount Sedom, on the southwest side of the lake, is a giant mountain of halite. |
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)
During 70,000 to 12,000 years ago the lake level was a 100-250 meters higher than its current level. This lake was termed "Lake Lisan", which fluctuated dramatically with rising to 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 with some significant drops and rises.
The Jordan River is the only major stream flowing into Dead Sea. There are no outlet streams.
The northern part of the Dead Sea receives scarcely 100 mm (4 inches) of rain a year. The southern section barely 50 mm (2 inches). 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".
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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 m 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). 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, after many centuries, finally mixed and the lake was a homogeneous body of water. Since then, the stratification has begun to redevelop.
The mineral content of the Dead Sea is significantly different from that of ocean water, consisting of approximately 53%
magnesium chloride, 37%
potassium chloride and 8% sodium chloride (common salt) with the remainder comprised of various trace elements.
The concentration of
sulfate, SO
42-, ions is very low, and the
bromide ion concentration is the highest of all waters on Earth. Chlorides neutralize most of the
calcium ions in the Dead Sea and its surroundings. While in other seas sodium chloride is 97% of the salts, in the Dead Sea the quantity of NaCl is only 12-18%. The water temperature varies from 19 °C in February to 31 °C in August.
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). Because of its unusually high concentration of salt, anyone can easily float in the Dead Sea because of natural
buoyancy as a result of the higher density of the water. In this the Dead Sea is similar to the
Great Salt Lake in
Utah, in the
United States.
The water of the Dead Sea has a greasy feel to it. The water stings cuts, and causes pain if it comes in contact with the eyes.
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 may be produced.
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.
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.
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Dead Sea in the morning, seen from Masada |
The sea is called "dead" because its high salinity means no fish or macroscopic aquatic organisms can live in it, though minuscule quantities of bacteria and microbial fungi are present.
In times of flood the salt content of the Dead Sea can drop from its usual 35% salinity to 30% or lower. In the wakes of rainy winters the Dead Sea temporarily comes to life. In 1980, after one such rainy winter, the normally dark blue Dead Sea turned red. Researchers from
Hebrew University found the Dead Sea to be teeming with a type of
algae called
Dunaliella. The
Dunaliella in turn nourished
carotenoid-containing (red-
pigmented)
halobacteria whose presence is responsible for the color change. Since 1980 the Dead Sea basin has been dry and the algae and the bacteria have not returned in measurable numbers.
Many animal species make their homes in the mountains surrounding the Dead Sea. A hiker can see
camels,
ibexes,
hares,
hyraxes,
jackals,
foxes, and even
leopards. Hundreds of
bird species inhabit the zone as well. Both Jordan and Israel have established nature reserves around the Dead Sea.
The delta of the Jordan river was formerly a veritable jungle of
papyrus and
palm trees.
Flavius Josephus described Jericho as "the most fertile spot in Judea". In Roman and Byzantine times
sugarcane,
henna, and
sycamore all made the lower Jordan valley quite wealthy. One of the most valuable products produced by Jericho was the sap of the
balsam tree, which could be made into
perfume.
By the nineteenth century Jericho's fertility was a thing of the past.
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World's lowest (dry) point, 1971 |
The human history of the Dead Sea goes all the way back to remote antiquity. Just north of the Dead Sea is
Jericho, the oldest continually occupied town in the world. Somewhere, perhaps on the Dead Sea's southeast shore, are the cities mentioned in the
Book of Genesis which were destroyed in the times of
Abraham:
Sodom and
Gomorra and the three other "Cities of the Plain". King David hid from
Saul at
Ein Gedi nearby.
The
Greeks knew the Dead Sea as "Lake
Asphaltites", due to the naturally surfacing asphalt.
Aristotle wrote about the remarkable waters. During the
Egyptian conquest it is said that Queen
Cleopatra obtained exclusive rights to build cosmetic and pharmaceutical factories in the area. Later, the
Nabateans discovered the value of
bitumen extracted from the Dead Sea needed by the Egyptians for
embalming their
mummies.
Herod the Great,
Jesus, and
John the Baptist were closely linked with the Dead Sea and its surroundings. In Roman times the
Essenes settled in
Qumran on the Dead Sea's northern shore. There, in the soft marl of the Dead Sea area, they carved out storage caves for their library. Two thousand years later their library was found and given the name "the
Dead Sea Scrolls".
King Herod built several palaces on the Western Bank of the Dead Sea. The most famous was
Masada, where, in 66-70 AD, a small group of rebellious Jewish
zealots held out against the might of the Roman Legion.
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.
In
Islamic
tradition, the Dead Sea was about the land in which the
Prophet Lut (
Lot in the Hebrew scriptures) lived. His tribe had done wrong and had therefore been given a punishment for such deeds. The punishment arrived when
angels were sent down by
Allah to Lut. The angels raised the land where the prophet's tribe lived and threw it back into the ground, causing the ground near the impact to cave in. Thus, the lowest land on Earth was formed because of this punishment. The sinners were destroyed and the followers were saved.
Bedouin tribes have continuously lived in this area, and more recently explorers and scientists arrived to analyze the minerals and conduct research into the unique climate. Since the 1960s,
tourists from all the over world have also explored the Dead Sea region.
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View of salt evaporation pans on the Dead Sea, taken in 1989 from the Space Shuttle Columbia. The southern half is now separated from the northern half at what used to be the Lisan Peninsula because of the fall of the level of Dead Sea. |
In the early part of the 20th century, the Dead Sea began to attract interest from chemists who deduced that the Sea was a natural deposit of
potash and
bromine. The
Palestine Potash Company was chartered in 1929 (after its founder, Moses Novomeysky, a Jewish engineer from
Siberia, worked for the charter for over ten years). The first plant was on the north shore of the Dead Sea at Kalia and produced potash, or potassium chloride, by solar evaporation of the brine. Employing
Arabs and
Jews, it was an island of peace in turbulent times. The company quickly grew into the largest industrial site in the Middle East and in 1934 built a second plant on the southwest shore, in the Sodom area, south of the 'Lashon' region of the Dead Sea. The Dead Sea Works Ltd. was established in 1952 as a state-owned company to extract potash and other minerals from the Dead Sea.
From the Dead Sea brine, Israel produces (2001) 1.77 million tons potash, 206,000 tons elemental bromine, 44,900 tons
caustic soda, 25,000 tons
magnesium metal, and sodium chloride. On the Jordanian side of the Dead Sea, the
Arab Potash Co. (APC), formed in 1956, produces 2.0 million tons of potash annually, as well as sodium chloride and bromine. Both companies use extensive salt evaporation pans that have essentially diked the entire southern end of the Dead Sea for the purpose of producing
carnallite, potassium magnesium chloride, which is then processed further to produce potassium chloride. The power plant on the Israeli side allows production of magnesium metal (by a subsidiary, Dead Sea Magnesium Ltd.). The salt evaporation pans are visible from space.
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Dead Sea at Dusk (from Suwayma, Jordan) |
The Dead Sea is rapidly shrinking because of diversion of incoming water. Between 1930 and 1997 it fell 21 m [
1]. Although the Dead Sea may never entirely disappear, because evaporation slows down as surface area decreases and saltiness increases, it is feared that the Dead Sea may substantially change its characteristics.
Since it is not realistic to cease using the Jordan River for human needs, one idea to save the Dead Sea is to channel water from the
Mediterranean or the
Red Sea, either through tunnels or canals. Although a Mediterranean structure would be shorter, Israel is now committed to building a Red Sea canal in deference to
Jordan's needs. The plan is to pump water 120 metres up the
Arava/Arabah from
Aqaba or
Eilat, tunnel under the highest point of the Arava/Arabah valley, and then canalize the river of seawater as it falls 520 metres to the Dead Sea. The desalination plant would be constructed in Jordan.
On
May 9,
2005, Jordan, Israel, and the
Palestinian Authority signed an agreement to begin feasibility studies on the project, to be officially known as the "
Two Seas Canal". The scheme calls for the production of 870 million cubic metres of fresh water per year and 550 mega
watts of electricity. The
World Bank is supportive of the project.
*
Seawater*
Two Seas Canal*
List of places on land with elevations below sea level* The deepest point on the Earth's crust is the
Mariana Trench, a submarine trench in the western
Pacific Ocean.
* There are ice-covered depressions on the continent of
Antarctica that are deeper than the Dead Sea (such as the
Bentley Subglacial Trench).
* The world's deepest lake is
Lake Baikal in Siberia.
* Yehouda Enzel, et al, eds (2006)
New Frontiers in Dead Sea Paleoenvironmental Research, Geological Society of America, ISBN 0-8137-2401-5 [
2]
*
Dead Sea photogeography and explication*
Dead Sea photos*
Dead Sea pictures *
The official Israeli site*
The Dead Sea Works (Israel Chemical Ltd) site*
Ezekiel's Water Project
