The Dead Sea (Hebrew ים המלח, Arabic البحر الميت) is the lowest point on the Earth's surface. It is on the border between Israel and Jordan on the Jordan Rift Valley . This endorheic body of water is the deepest hypersaline lake in the world.

The Dead Sea has attracted interest and visitors from around the Mediterranean basin for thousands of years. It was a place of refuge for David, it was one of the world's first health resorts for Herod, it was been the supplier of products as diverse as balms for Egyptian mummification to potash for fertilizers.

The Dead Sea is not called "the Dead Sea" in non-European languages. In Hebrew the Dead Sea is called the "Yam ha-Melah" - meaning "Salt Sea." In past times it was the "Eastern Sea" or the "Sea of Arava." In Arabic the Dead Sea is called "Bahr al-Lut," 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)

The surface of the Dead Sea is the at an elevation of 417m (465yd) below sea level (2003 figure).

Contents

1 Natural History 2 Chemistry and Health Effects 3 Flora and Fauna 4 Human History

Natural History

The Dead Sea is part of a long fissure in the Earth's surface called the Great Rift Valley. The 3700 mile long Great Rift Valley extends from Zambezi Valley in southern Africa to the Taurus Mountains of Turkey. The Great Rift Valley formed in Cretaceous times as a result of the Arabian plate moving northward and then eastward away from Africa.

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 what is now 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, but each deluge deposited beds of salt, eventually coming to be two miles thick.

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 with a name is called "Lake Samra." Lake Samra was a freshwater or brackish lake that extended at least fifty miles south of the current southern end of the Dead Sea and sixty miles north, well above the present Hula Depression. As the climate turned more arid and hotter Lake Samra shrank and became saltier. The large, saltwater predecessor of the Dead Sea being called "Lake Lisan."

In prehistoric times great amounts of sediment collected on the floor of Lake Samra. 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 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)

The period 23,000 years ago to 18,000 years ago was very dry and the surface level of Lake Lisan fell to a point well below the Dead Sea's surface level today. At the sea's minimum, its waters may have been 2,100 feet below sea level.

Around 12,000 years ago this tiny puddle of the Lake Lisan minimum began to steadily grow again. By Biblical times the Dead Sea was about as large as its northern basin is today. There was no southern basin until the late Middle Ages.

The northern part of the Dead Sea receives scarcely four inches of rain a year. The southern section barely two 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 southeastern side of the lake is a 700' tall halite formatation called "Mount Sedom ."

Chemistry and Health Effects

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 120' or so of the Dead Sea had a salinity that ranged between 300 and 400 parts per thousand and a temperature that swung between 66 F and 98 F. Underneath a zone of transition, the lowest level of the Dead Sea had waters of a consistent 72 F temperature and complete saturation of 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 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 homogenous 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 (table salt) with the remainder comprised of various trace elements.

The concentration of SO₄ ions is very low, and the bromine ions 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 NaCl is 97%, in the Dead Sea the quantity of the NaCl is only 12-18 percent. The water temperature goes from 19 degrees Celsius in February to 31 degrees Celsius in August.

The water of the Dead Sea contains 21 minerals including magnesium, calcium, bromine and potassium. Twelve of these are found in no other sea or ocean, and some are recognized for imparting a relaxed feeling, nourishing the skin, activating the circulatory system and for easing rheumatic discomfort and metabolic disorders. Comparison between the chemical composition of the Dead Sea to other lakes and oceans show that the salt's concentration in the Dead Sea is 31.5% (the salinity fluctuates somewhat). Because of its unusually high concentration of salt, anyone can float in the Dead Sea easily because of natural buoyancy.

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 large chunks, as large as houses, are 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.

Sunlight at the Dead Sea is high in therapeutic UVA rays and low in burning UVB, so extended exposure is safe and low-risk. The filtering effect comes from a thick atmosphere: the Dead Sea is about 1,200 feet below sea level and the ozone layer above it is minimally depleted. The Dead Sea is the only place on Earth where you can sunbathe for extended periods with little or no sunburn because harmful ultraviolet rays are filtered through three natural layers: an extra atmospheric layer, an evaporation layer that exists above the Dead Sea, and a rather thick ozone layer-even though CFCs are gradually eating it away elsewhere. The light at the Dead Sea is said to be especially good for people suffering from psoriasis.

Flora and Fauna

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.

Fish that are carried into the Dead Sea by the Jordan river or by streams die as soon as the freshwater mixes with the hypersaline waters of the Dead Sea. The mixing process, however, is not immediate, and sometimes freshwater can float indefinitely on the Dead Sea's surface. Thus, it is sometimes possible for fish to live "on" the surface of the Dead Sea for a few days, though never "in" the Dead Sea itself.

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 temporalily 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 halobacteria whose red carotenoids in the were 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, jackals, foxes, and even leopards. Both Jordan and Israel have established nature reserves around the Dead Sea. There are hundreds of bird species that inhabit the zone as well.

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, of which could be made perfume.

Agriculture in Palestine declined after the Arab conquest. By the Nineteenth century Jericho's fertility was a thing of the past.

Human History

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 Sodom and Gomorra and the three other "Cities of the Plain." King David hid from Saul by Ein Gedi.

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 wily Nabateans discovered the value of bitumen extracted from the Dead Sea needed by the Egyptians for embalming their mummies.

King Herod, 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. Bedouin tribes have continuously lived in the 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.

In the early part of the 20th century the Dead Sea began to attract interests 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, a Jewish engineer from Siberia, worked for the charter for over ten years). The original Palestine Potash Company was located at the north end of the lake, in what is now the West Bank. 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 later built a second