The Dead Sea (Hebrew: יָם הַמֶּלַח About this sound Yam ha-Melah lit. Salt Sea, Arabic: البحر الميت About this sound Al-Bahr al-Mayyit), is a salt lake bordered by Jordan to the east and Israel and Palestine to the west. Its surface and shores are 430.5 metres (1,412 ft) below sea level, Earth's lowest elevation on land. The Dead Sea is 304 m (997 ft) deep, the deepest hypersaline lake in the world. With 34.2% salinity (in 2011), it is 9.6 times as salty as the ocean, and one of the world's saltiest bodies of water. This salinity makes for a harsh environment in which plants and animals cannot flourish, hence its name. The Dead Sea is 50 kilometres (31 mi) long and 15 kilometres (9 mi) wide at its widest point. It lies in the Jordan Rift Valley and its main tributary is the Jordan River.
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 fertilizers. People also use the salt and the minerals from the Dead Sea to create cosmetics and herbal sachets.
The Dead Sea water has a density of 1.24 kg/litre, which makes swimming similar to floating.
The Dead Sea is receding at an alarming rate. Multiple canals and pipelines were proposed to reduce its recession, which had begun causing many problems. The Red Sea–Dead Sea Water Conveyance project, carried out by Jordan, will provide water to neighboring countries, while the brine will be carried to the Dead Sea to help stabilize its levels. The first phase of the project is scheduled to begin in 2018 and be completed in 2021.
The Dead Sea area has become a location for health research and potential treatment for several reasons. The mineral content of the water, the 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 may have specific health effects. For example, persons experiencing reduced respiratory function from diseases such as cystic fibrosis seem to benefit from the increased atmospheric pressure.
The region's climate and low elevation have made it a popular center for assessment of putative therapies:
Climatotherapy: Treatment which exploits local climatic features such as temperature, humidity, sunshine, barometric pressure and special atmospheric constituents
Heliotherapy: Treatment that exploits the biological effects of the sun's radiation
Thalassotherapy: Treatment that exploits bathing in Dead Sea water
Climatotherapy at the Dead Sea may be a therapy for psoriasis by sunbathing for long periods in the area due to its position below sea level and subsequent result that UV rays are partially blocked by the increased cloud cover over the Dead Sea.
Rhinosinusitis patients receiving Dead Sea saline nasal irrigation exhibited improved symptom relief compared to standard hypertonic saline spray in one study.
Dead Sea mud pack therapy has been suggested to temporarily relieve pain in patients with osteoarthritis of the knees. According to researchers of the Ben Gurion University of the Negev, treatment with mineral-rich mud compresses can be used to augment conventional medical therapy.
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.
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 climate change. The Sedom Lagoon deposited beds of salt that eventually became 2.5 km (1.55 mi) thick.