Great Salt Lake, shallow body of saltwater, NW Utah, between the Wasatch Range on the east and the Great Salt Lake Desert on the west; largest salt lake in North America. Fed by the Weber, Jordan, and Bear rivers, the lake varies greatly in size and depth according to weather changes. Its average depth ranges from 13 to 24 ft (4 to 7.3 m). From 1,000 sq mi (2,590 sq km) in the period between 1955 and 1975, the lake expanded to its modern maximum of almost 2,500 sq mi (6,477 sq km) by the mid-1980s. Storage of spring run-off in reservoirs to meet domestic and industrial demands for water have contributed to seasonal lake shrinkage. The salt content, nearly 10% at its greatest size, increases as the water level decreases. Magnesium chloride, potash, and common salt are commercially extracted from the lake. The heavy brine supports no life except brine shrimp and colonial algae. The Great Salt Lake is a remnant of prehistoric Lake Bonneville, which covered an extensive area of the Great Basin and was once c.1,000 ft (305 m) deep. Its various levels are marked by former beachlines on the mountains and by rich soil deposits on the terraces to the east, where irrigated farming is practiced. Antelope and Fremont islands are the largest islands in the lake; the smaller islands are rookeries for sea gulls and other birds. Promontory Point, a mountainous peninsula 20 mi (32 km) long, extends into the lake from the north; a railroad cutoff on a causeway passes through the neck as it crosses the lake and the Great Salt Lake Desert from Ogden to Lucin, Utah. The Bonneville Salt Flats, in the western part of the desert, is a world-famous automobile racing ground. In 1845 the U.S. explorer John Frémont became the first person to cross the salt desert.
See D. L. Morgan, The Great Salt Lake (1986); H. Stansbury, Exploration of the Valley of the Great Salt Lake (1988).