Dead Sea

Dead Sea

Dead Sea

The Dead Sea (Hebrew: [[wikt:ים המלח, Yam hamMelaḥ; Arabic: [[wikt:البحر الميت, Āl-Baḥrū l-Maytū), also known by other names, is a salt lake bordered by Jordan to the east and the West Bank and Israel to the west. It lies in the Jordan Rift Valley, and its main tributary is the Jordan River.

As of 2019, the lake's surface is below sea level, making its shores the lowest land-based elevation on Earth. It is deep, the deepest hypersaline lake in the world. With a salinity of 342 g/kg, or 34.2% (in 2011), it is one of the world's saltiest bodies of water – 9.6 times as salty as the ocean – and has a density of 1.24 kg/litre, which makes swimming similar to floating. This salinity makes for a harsh environment in which plants and animals cannot flourish, hence its name. The Dead Sea's main, northern basin is long and wide at its widest point.

The Dead Sea has attracted visitors from around the Mediterranean Basin for thousands of years. It was one of the world's first health resorts (for Herod the Great), and it has been the supplier of a wide variety of products, from asphalt for Egyptian mummification to potash for fertilisers. Today, tourists visit the sea on its Israeli, Jordanian and West Bank coastlines. The Palestinian tourism industry has been met with setbacks in developing along the West Bank coast.

The Dead Sea is receding at a swift rate; its surface area today is , having been in 1930. Multiple canal and pipeline proposals, such as the scrapped Red Sea–Dead Sea Water Conveyance project, have been made to reduce its recession.

Names

The English name "Dead Sea" is a calque of the Arabic name or lang , itself a calque of earlier Greek and Latin names in reference to the scarcity of aquatic life caused by the lake's extreme salinity. The name also occasionally appears in Hebrew literature as , 'Sea of Death'.

The usual biblical and modern Hebrew name for the lake is the (lang). Other Hebrew names for the lake also mentioned in the Bible are the and the . In Arabic, it is also known as the (or) from the nephew of Abraham whose wife was said to have turned into a pillar of salt during the destruction of Sodom and Gomorrah. Less often, it has been known in Arabic as the from a formerly important city along its shores.

Historical English names include the , from the biblical account of its destruction and from Greek and Latin. Because of the large volume of ancient trade in the lake's naturally occurring free-floating bitumen, its usual names in ancient Greek and Roman geography were some form of (or , or ; Latin: [[:wikt:lacus) or Sea .

Geography

The Dead Sea is an endorheic lake located in the Jordan Rift Valley, a geographic feature formed by the Dead Sea Transform (DST). This left lateral-moving transform fault lies along the tectonic plate boundary between the African Plate and the Arabian Plate. It runs between the East Anatolian Fault zone in Turkey and the northern end of the Red Sea Rift offshore of the southern tip of Sinai. It is here that the Upper Jordan River/Sea of Galilee/Lower Jordan River water system comes to an end.

The Jordan River is the only major water source flowing into the Dead Sea, although there are small perennial springs under and around the Dead Sea, forming pools and quicksand pits along the edges. There are no outlet streams.

The Mujib River, biblical Arnon, is one of the larger water sources of the Dead Sea other than the Jordan. The Wadi Mujib valley, 420 m below the sea level in the southern part of the Jordan valley, is a biosphere reserve, with an area of . Other more substantial sources are Wadi Darajeh (Arabic)/Nahal Dragot (Hebrew), and that ends at Ein Gedi. Wadi Hasa (biblical Zered) is another wadi flowing into the Dead Sea.

Rainfall is scarcely per year in the northern part of the Dead Sea and barely in the southern part. The Dead Sea zone's aridity is due to the rainshadow effect of the Judaean Mountains. The highlands east of the Dead Sea receive more rainfall than the Dead Sea itself.

To the west of the Dead Sea, the Judaean mountains rise less steeply and are much lower than the mountains to the east. Along the southwestern side of the lake is a tall halite mineral formation called Mount Sodom.

Geology

Formation theories

There are two contending hypotheses about the origin of the low elevation of the Dead Sea. The older hypothesis is that the Dead Sea lies in a true rift zone, an extension of the Red Sea Rift, or even of the Great Rift Valley of eastern Africa. A more recent hypothesis is that the Dead Sea basin is a consequence of a "step-over" discontinuity along the Dead Sea Transform, creating an extension of the crust with consequent subsidence.

Sedom Lagoon

During the late Pliocene-early Pleistocene, around 3.7 million years ago, what is now the valley of the Jordan River, Dead Sea, and the northern Wadi Arabah was repeatedly inundated by waters from the Mediterranean Sea. The waters formed in a narrow, crooked bay that is called by geologists the Sedom Lagoon, 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 changes in the tectonic and climatic conditions.

The Sedom Lagoon extended at its maximum from the Sea of Galilee in the north to somewhere around south of the current southern end of the Dead Sea, and the subsequent lakes never surpassed this expanse. The Hula Depression was never part of any of these water bodies due to its higher elevation and the high threshold of the Korazim block separating it from the Sea of Galilee basin.

Salt deposits

The Sedom Lagoon deposited evaporites mainly consisting of rock salt, which eventually reached a thickness of on the old basin floor in the area of today's Mount Sedom.

Lake formation

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 lagoon became a landlocked lake.

The first prehistoric lake to follow the Sedom Lagoon is named Lake Amora (which possibly appeared in the early Pleistocene; its sediments developed into the Amora (Samra) Formation, dated to over 200–80 kyr BP), followed by Lake Lisan (c. 70–14 kyr) and finally by the Dead Sea.

Lake salinity

The water levels and salinity of the successive lakes (Amora, Lisan, Dead Sea) have either risen or fallen as an effect of the tectonic dropping of the valley bottom, and due to climate variation. As the climate became more arid, Lake Lisan finally shrank and became saltier, leaving the Dead Sea as its last remainder.

From 70,000 to 12,000 years ago, Lake Lisan's level was to higher than its current level, possibly due to lower evaporation than in the present. Its level fluctuated dramatically, rising to its highest level around 26,000 years ago, indicating a very wet climate in the Near East. Around 10,000 years ago, the lake's level dropped dramatically, probably even lower than today. During the last several thousand years, the lake has fluctuated approximately , 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.

Salt mounts formation

In prehistoric times, great amounts of sediment collected on the floor of Lake Amora. The sediment was heavier than the salt deposits and squeezed the salt deposits upwards into what are now the Lisan Peninsula and Mount Sodom (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 bucket. When the floor of the Dead Sea dropped further due to tectonic forces, the salt mounts of Lisan and Mount Sodom stayed in place as high cliffs (see salt dome).

Chemistry

With 34.2% salinity (in 2011), it is one of the world's saltiest bodies of water, though Lake Vanda in Antarctica (35%), Lake Assal in Djibouti (34.8%), Lagoon Garabogazköl in the Caspian Sea (up to 35%) and some hypersaline ponds and lakes of the McMurdo Dry Valleys in Antarctica (such as Don Juan Pond (44%)) have reported higher salinities.

In the 19th century and the early 20th century, the surface layers of the Dead Sea were less salty than today, which resulted in an average density in the range of 1.15-1.17 g/cm3 instead of the present value of around 1.25 g/cm3. A sample tested by Bernays in the 19th century had a salinity of 19%. By the year 1926, the salinity had increased (although it was also suspected that the salinity varies seasonally and depends on the distance from the mouth of the Jordan).

Until the winter of 1978–79, when a major mixing event took place, the Dead Sea was composed of two stratified layers of water that differed in temperature, density, age, and salinity. The topmost or so of the Dead Sea had an average salinity of about 30%, and a temperature that swung between and . Underneath a zone of transition, the lowest level of the Dead Sea had waters of a consistent temperature, salinity of over 34%, and complete saturation of sodium chloride (NaCl). Since the water near the bottom is saturated with NaCl, that 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 was saltier than the lower layer. Nevertheless, the upper layer remained suspended above the lower layer because its waters were warmer and thus less dense. When the upper layer cooled so its density was greater than the lower layer, the waters mixed (1978–79). For the first time in centuries, the lake was a homogeneous body of water. Since then, stratification has begun to redevelop.

The mineral content of the Dead Sea is very different from that of ocean water. The exact composition of the Dead Sea water varies mainl…

Text taken from Wikipedia - Dead Sea under the CC-BY-SA-3.0 on April 13, 2023

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