The Dead Sea (Sea of Salt) (The Sea of Death), also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and Palestine to the west. The Dead Sea is the lowest point on earth in any land mass (417 meters below sea level, to be exact). The quantity of water that evaporates from it is greater than that which flows into it, such that this body of water has the highest concentration of salt in the world (340 grams per liter of water). The Dead Sea is 377 m (1,237 ft) deep, making it the deepest hypersaline lake in the world. A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride or other mineral salts, with saline levels surpassing that of ocean water. The Dead Sea’s unusually high salt concentration means that people can easily float in the Dead Sea due to natural buoyancy. In this respect the Dead Sea is similar to the Great Salt Lake in Utah in the United States. This salinity makes for a harsh environment in which animals cannot flourish (hence its name). The Dead Sea is 67 kilometres (42 mi) long and 18 kilometres (11 mi) wide at its widest point. It lies in the Jordan Rift Valley and its main tributary is the Jordan River. The Dead Sea area has become a major center for health research and treatment for several reasons. The mineral content of the water, 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.