GREAT SALT LAKE, a shallow body of highly concentrated brine in the N.W. part of Utah, U.S.A., lying between 1 18.8° and 113.2° W. long. and between 40.7° and 41.8° lat. Great Salt Lake is 4218 ft. above sea-level. It has no outlet, and is fed chiefly by the Jordan, the Weber and the Bear rivers, all draining the mountainous country to the E. and S.E. The irregular outline of the lake has been compared to the roughly drawn hand, palm at the S., thumb (exaggerated in breadth) pointing N.E., and the fingers (crowded together and drawn too small) reaching N.
No bathymetric survey of the lake has been made, but the maximum depth is 60 ft. and the mean depth less than 20 ft., possibly as little as 13 ft. The lake in 1906 was approximately 75 m. long., from N.W. to S.E., and had a maximum width of 50 m. and an area of 1750 sq. m. This area is not constant, as the water is very shallow at the margins, and the relation between supply from precipitation, &c., and loss by evaporation is variable, there being an annual difference in the height of the water of 15-18 in. between June (highest) and November (lowest), and besides a difference running through longer cycles: in 1850 the water was lower and the lake smaller than by any previous observations (the area and general outline were nearly the same again in 1906); then the water rose until 1873; and between 1886 and 1902 the fall in level was II-6 ft. The range of rise and fall from 1845 to 1886 was 13 ft., this being the rise in 1865-1886. With the fall of water there is an increase in the specific gravity, which in 1850 was 1.17, and in September 1901 was I179; in 1850 the proportion of solids by weight was 22.282%, in September 1901 it was 25.221; at the earlier of these dates the solids in a litre of water weighed 260.69 grams, at the latter date 302'122 grams. The exact cause of this cyclic variation is unknown: the low level of 1906 is usually regarded as the result of extensive irrigation and ploughing in the surrounding country, which have robbed the lake, in part, of its normal supply of water. It is also to be noted that the rise and fall of the lake level have been coincident, respectively, with continued wet and dry cycles. That the lake will soon dry up entirely seems unlikely, as there is a central trough, 25 to 30 m. wide, about 40 ft. deep, running N.W. and S.E. The area and shore-line of the lake are evidently affected by a slight surface tilt, for during the same generation that has seen the recent fall of the lake level the shore-line is in many cases 2 m. from the old, and fences may be seen a mile or more out in the lake. The lake bed is for the most part clear sand along the margin, and in deeper water is largely coated with crusts of salt, soda and gypsum.
The lake is a novel and popular bathing resort, the specific gravity of the water being so great that one cannot sink or entirely submerge oneself. There are well-equipped bathing pavilions at Garfield and Saltair on the S. shore of the lake about 20 m. from Salt Lake City. The bathing is invigorating; it must be followed by a freshwater bath because of the incrustation of the body from the briny water. The large amount of salt in the water makes both fauna and flora of the lake scanty; there are a few algae, the larvae of an Ephydra and of a Tipula fly, specimens of what seems to be Corixa decolor, and in great quantities, so as to tint the surface of the water, the brine shrimp, Artemia salina (or gracilis or fertilis), notable biologically for the rarity of males, for the high degree of parthenogenesis and for apparent interchangeableness with the Branchipus. The lake is of interest for its generally mountainous surroundings, save to the N.W., where it skirts the Great Salt Lake Desert, for the mountainous peninsula, the Promontory, lying between thumb and fingers of the hand, shaped like and resembling in geological structure the two islands S. of it, Fremont and Antelope,' and the Oquirrh range S. of the lake. The physiography of the surrounding country shows clearly that the basin occupied by Great Salt Lake is one of many left by the drying up of a large Pleistocene lake, which has been called lake Bonneville. Welldefined wave-cut cliffs and terraces show two distinct shore-lines of this early lake, one. the "Bonneville Shore-line," about 1000 ft. above Great Salt Lake, and the other, the "Provo Shoreline," about 625 ft. higher than the present lake. These shorelines and the presence of two alluvial deposits, the lower and the larger of yellow clay 90 ft. deep, and, separated from it by a plane of erosion, the other, a deposit of white marl, 10-20 ft. deep, clearly prove the main facts as to lake Bonneville: a dry basin was first occupied by the shallow waters of a small lake; then, during a long period of excessive moisture (or cold), the waters rose and spread over an area nearly as large as lake Huron with a maximum depth of 1000 ft.; a period of great dryness followed, in which the lake disappeared; then came a second, shorter, but more intense period of moisture, and in this time the lake rose, covered a larger area than before, including W. Utah and a little of S. Idaho and of E. Nevada, about 19,750 sq. m., had a very much broken shore-line of 2550 m. and a maximum depth of 1050 ft. and a mean depth of Boo ft., overflowed the basin at the N., and by a tributary stream through Red Rock Pass at the N. end of the Cache valley poured its waters into the Columbia river system. The great lake was then gradually reduced by evaporation, leaving only shallow bodies of salt water, of which Great Salt Lake is the largest. The cause of the climatic variations which brought about this complex history of the Salt Lake region is not known; but it is worthy of note that the periods of highest water levels were coincident with a great expansion of local valley glaciers, some of which terminated in the waters of lake Bonneville.
Industrially Great Salt Lake is of a certain importance. In early days it was the source of the salt supply of the surrounding country; and the manufacture of salt is now an important industry. The brine is pumped into conduits, carried to large ponds and there evaporated by the sun; during late years the salt has been refined here, being purified of the sulphates and magnesium compounds which formerly rendered it efflorescent and of a low commercial grade. Mirabilite, or Glauber's salt, is commercially valuable, occurring in such quantities in parts of the lake that one may wade knee-deep in it; it separates 1 Besides these islands there are a few small islands farther N., and W. of Antelope, Stansbury Island, which, like Antelope and Fremont Islands, is connected with the mainland by a bar sometimes uncovered and rarely in more than a foot of water.
from the brine at a temperature between 30° and 20° F. The lake is crossed E. and W. by the Southern Pacific railway's so-called "Lucin Cut-off," which runs from Ogden to Lucin on a trestle with more than 20 m. of "fill"; the former route around the N. end of the lake was 43 m. long.
Great Salt Lake was first described in 1689 by Baron La Hontan, who had merely heard of it from the Indians. "Jim" Bridger, a famous mountaineer and scout, saw the lake in 1824, apparently before any other white man. Captain Bonneville described the lake and named it after himself, but the name was transferred to the great Pleistocene lake. John C. Fremont gave the first description of any accuracy in his Report of 1845. But comparatively little was known of it before the Mormon settlement in 1847. In 1850 Captain Howard Stansbury completed a survey, whose results were published in 1852. The most extensive and important studies of the region, however, are those by Grove Karl Gilbert of the United States Geological Survey, who in 1879-1890 studied especially the earlier and greater lake.
See J. E. Talmage, The Great Salt Lake, Present and Past (Salt Lake City, 1900); and Grove Karl Gilbert, Lake Bonneville, monograph i of United States Geological Survey (Washington, 1890), containing (pp. 12-19) references to the earlier literature.
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