A second clue to how the sea became salty is the presence of salt lakes such as the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than seawater. Lakes are temporary storage areas for water. Rivers and streams bring water to the lakes, and other rivers carry water out of lakes. Thus, lakes are really only wide depressions in a river channel that have filled with water.
Water flows in one end and out the other.
The Great Salt Lake, Dead Sea, and other salt lakes have no outlets. All the water that flows into these lakes escapes only by evaporation. When water evaporates, the dissolved salts are left behind. So a few lakes are salty because rivers carried salts to the lakes, the water in the lakes evaporated and the salts were left behind. After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels.