GREAT SALT LAKE, a large body of shallow, briny water in north-western Utah, U.S.A., situated about 4,20o ft. above sea-level. The lake was first accurately described by John C.
Fremont in 1845, and was carefully surveyed in 1849 and 185o by Capt. Howard Stansbury. The lake and the surrounding region were studied in 1890 by G. K. Gilbert, who gave a detailed description of it and of an earlier and greater lake, Lake Bonne ville (see UTAH) that covered its site and a large adjacent area.
Great Salt Lake has no outlet and is fed chiefly by the Jordan, Weber and Bear rivers, which flow from the mountains east and south-east of the lake. Since 185o its area has varied from 1,75o to about 1,50o sq.m., its present area, and its mean depth has varied from 25 to 15 feet. The seasonal variation in its level, due to melting snow on the mountains, is about 16 inches. The inflow of water and the area of the lake have been diminished by irrigation, which increases evaporation. The salinity of the lake increases as its area decreases. The water has contained from 14 to 23% of saline matter, principally sodium chloride. Its average salinity is now nearly six times that of the ocean. It contains also sodium sulphate and other minerals. Although the waters of the Jordan, Weber and Bear rivers are considered fresh, they carry into the lake enough mineral matter to keep its water nearly at the point of saturation.
When the temperature of the water falls below 2o° F the salt begins to be precipitated. Salt is obtained from the lake and marketed profitably, but not in quantities large enough to reduce perceptibly the salinity of the water. The lake contains several islands and is crossed west of Ogden by the Southern Pacific rail way, over what is called the Lucin cut-off, a trestle and a gravel fill about 27 m. long. Its bed consists mainly of sand, but along its shores there are crusts of common salt, sodium sulphate and gypsum. The specific gravity of the water is so great that a swimmer can not sink in it. In the lake are a few species of seaweed (algae), the larvae of two genera of flies (Ephydra and Tipula), an insect belonging to the genus Corixa and a brine shrimp (Artemia).
Lake Bonneville was more than i,000 ft. above the level of Great Salt Lake, and lasted long enough to form beaches still be plainly traced. Below the Bonneville terraces there are others, the most conspicuous of which form what is called the Provo shore line, which is 625 ft. above the present level of Great Salt Lake.
See I. C. Russell, Lakes of North America (New York, 1895) ; J. E. Talmage, The Great Salt Lake, Present and Past (Salt Lake City, 1900) ; G. K. Gilbert sketch in U.S. Geological Survey Bulletin 612, PP. (Washington 1915) . (G. McL. Wo.)