What is now the Dead Sea was once connected to the Red Sea starting around three million years ago. Around two million years ago the land arose significantly enough to cut off the interior body of water from the Red Sea. The Dead Sea's predecessor, Lake Gomorrah, was larger than the sea today but as the climate changed the lake became smaller and smaller. The salt had no where to go and the lake became saltier.
Today the Dead Sea about thirty-five percent salt (about nine times more than the ocean). Salt is so prevenlant that no complex life can live in the sea and the nearby landforms are formed from halite. The sheer amount of salinity allows for people to float on the surface.
The sea air, mineral water, and low ultraviolet radiation among other factors allows the Dead Sea to be a health retreat. King Herod the Older made a health spa along the shores for his benefit.
History has many sites along the coast. David hid from Saul here, Cleopatra had cosmetic factories nearby, Egyptians obtained embalming chemicals for their mummies from the sea, Masada and the cell of John the Baptist are close as well. And who can forget the Dead Sea Scrolls?
The Dead Sea has been shrinking lately. In the past few decades the sea has dropped more than seventy feet. The reason is because the only feeder, the Jordan River, is being irrigated for drinking, economical, and agricultural purposes. The Dead Sea Canal project has been proposed to stem the drop and hopefully refill the Dead Sea. However, geopolitics, economics, and chemistry are obstacles in the projects way.
The Dead Sea has survived millions of years of geological and climate change. Simple chemistry will prevent it from completely evaporating even if more water is pumped from the Jordan. However, environmental planning should be done to save this historical and geographical marvel.