
The lake is the largest remnant of Lake Bonneville, a prehistoric pluvial lake that once covered much of western Utah. The three major tributaries to the lake, the Jordan, Weber, and Bear rivers together deposit around 1.1 million tons of minerals in the lake each year. As it is endorheic (has no outlet besides evaporation), it has very high salinity, far saltier than seawater, and its mineral content is constantly increasing. Its shallow, warm waters cause frequent, sometimes heavy lake-effect snows from late fall through spring.
Although it has been called "America's Dead Sea", the lake provides habitat for millions of native birds, brine shrimp, shorebirds, and waterfowl, including the largest staging population of Wilson's phalarope in the world.
The Great Salt Lake is a remnant of a much larger prehistoric lake called Lake Bonneville. At its greatest extent, Lake Bonneville spanned 22,400 square miles (58,000 km2), nearly as large as present-day Lake Michigan, and roughly ten times the area of the Great Salt Lake today. Bonneville reached 923 ft (281 m) at its deepest point, and covered much of present-day Utah and small portions of Idaho and Nevada during the ice ages of the Pleistocene Epoch.
Lake Bonneville existed until about 16,800 years ago, when a large portion of the lake was released through the Red Rock Pass in Idaho. With the warming climate, the remaining lake began to dry, leaving the Great Salt Lake, Utah Lake, Sevier Lake, and Rush Lake behind.