Masada was the scene of a three-year siege that culminated in the mass suicide of its Jewish zealot defenders and the destruction of the fortress by the Romans in AD 73. The Jewish sect that left the biblical manuscripts known as the Dead Sea scrolls took shelter in caves to the northwest of the lake. It is a sunken block confined by two parallel geological faults. The eastern fault, along the edge of the Moab plateau, is more readily visible from the lake than is the western fault, which marks the gentler Judaean upfold. The Dead Sea is situated in a desert.
Rainfall is scantly and irregular.
Al-Lisan has about 2.5 inches of rain a year and the town of Sedom only about 2 inches. Evaporation of the lake's waters is estimated to average about 55 inches a year often creates a thick mist above the lake. On the rivers the atmospheric humidity varies from 45 percent in May to 62 percent in October. Lake and land breezes, which are relatively common, blow off the lake in all directions in the daytime and then reserve direction to blow toward the center of the lake at the night. The waters of the Dead Sea are extremely saline, and the concentration of salt increases toward the bottom.