The Dead Sea sits on top of the Dead Sea Rift, a tectonic fault line between the Arabian and the African plates. The movement of these plates causes the Dead Sea to sink about one meter per year! The Dead Sea used to be connected to the Mediterranean Ocean, but over a geologic time scale, it became cut off and evaporation concentrated the salt in the water so that today, the Dead Sea is 30 to 31 percent mineral salts. It has the highest level of salinity of any body of water in the world.
The lowest point on land in the Western Hemisphere is Death Valley in California at 86 meters below sea level.
The lowest point on the Earth's crust is the Mariana's Trench in the North Pacific Ocean. It is 11 kilometers deep. Like many of Earth's extremes, the Mariana's Trench is caused by the Pacific tectonic plate subducting beneath the Philippine plate; this means that the Pacific Plate is sliding underneath the Philippine plate. The point where the Philippine plate overlaps is Mariana's Trench.