USGS Logo Geological Survey Bulletin 707
Guidebook of the Western United States: Part E. The Denver & Rio Grande Western Route


A few one-day trips may be made by rail from Salt Lake City, either for pleasure, for seeing the surrounding country, or for studying some of the larger mines or mining districts.


As Great Salt Lake is the one natural feature which can not be duplicated in any other part of the country, people are naturally curious to see it and to have a chance to bathe in its waters. Many are familiar with the salt water of the ocean, but a large lake containing salt water is to most people a novelty. As the shores of Great Salt Lake are 10 miles from the city, the trip is generally made by rail. A large and ornate pavilion, called Saltair, has been built at the water's edge, and the traveler may enjoy bathing in the salt water or dancing in the pavilion. The facilities for dancing are not out of the ordinary, but the bathing, on account of the high mineral content of the water and its consequent density, is peculiar. Only with difficulty can the bather keep his feet from rising to the surface, and if he balances himself in an upright position only the lower part of the body is in the water and the head and shoulders rise above it. On account of the heaviness of the water the traveler may be interested in knowing something of the history of Great Salt Lake, as it is known to geologists, and the reason for its intense saltiness.84

84The following description of Great Salt Lake was written by G. K. Gilbert, who made an exhaustive study of the subject:

"Great Salt Lake has no outlet. Jordan River, which enters it from the south, is the outlet of Utah Lake. Bear River, coming from the north, carries the outflow from Bear Lake. The waters of Utah and Bear lakes and of Jordan and Bear rivers are fresh, and so is the water of Weber River, the third great tributary of Great Salt Lake, but the lake into which the three rivers flow is saline. It is saline because it has no outlet. The fresh waters of the rivers contain some saline matter, but the quantity is too small to be discovered by taste. As stated by the chemist, in parts per million, the quantity seems minute, but when account is taken also of the total volume of water brought by the streams to the lake in a year their burden of saline matter is found to be really great, amounting annually to more than 500,000 tons. Year by year and century by century the water which they pour into the lake is evaporated, but the dissolved solids can not escape in that way and therefore remain. They have accumulated until the lake water is approximately saturated, holding nearly as much mineral matter as it can retain in solution. The lake contains over 5,000,000,000 tons of common salt and about 900,000,000 tons of Glauber's salt, or sodium sulphate, as well as other mineral matter.

"Another consequence of the lack of outlet is that the lake varies from time to time in size. Whenever the gain from inflow is greater than the loss from evaporation the level of the water surface rises; when the loss is greater it falls. Each year there is a rise, beginning in winter, when the cool air has little power to absorb moisture, and continuing through spring, when the rivers are swollen by the melting of snows in the mountains. Each year there is a fall, beginning in summer, when the hot air rapidly absorbs the water, and continuing in autumn, when the rivers are smallest. This annual oscillation amounts on the average to about 16 inches.

"In some years the rainfall and snowfall are greater than in others, and then the lake usually receives more water than it parts with, so that the surface is left higher than it was before. In a series of wet years the lake level progressively rises; in a series of dry years it progressively falls; and as the rainfall is irregular the fluctuations of the lake are conspicuous. Since definite knowledge of the lake began in 1850 there have been five periods of increase and four of decrease. (See fig. 62.) The summer levels of 1868 and 1877 were more than 10 feet above the summer level of 1850, and those of 1903 and 1905 were 4 feet below that of 1850. The level of 1914 was 6 feet above that for 1905.

FIGURE 62.—Fluctuation in level of Great salt Lake from 1850 to 1914, as determined by gage readings or computed from precipitation records.

"The land bordering the lake has in many places a slope so gentle that a small change in the height of the water surface makes a great change in the area of the lake. On a map completed in 1850 the area shown is 1,750 square miles; on a map made in 1869 it is 2,170 square miles. In the interval between the two surveys the lake had risen 10 feet and this rise enlarged the area about 24 per cent. From the greater surface the evaporation was of course greater, and the dependence of evaporation on area is thus an important factor in regulating the size of the lake. The effect of a long series of wet years is somewhat reduced by the resulting increase of evaporation surface, and the effect of a series of dry years is lessened by the resulting reduction of surface exposed to evaporation. This natural and automatic control limits the range of oscillation and gives a certain permanence to what may be called a normal or average level. A change in the normal can occur only when some new factor is introduced.

"Both man and nature have introduced new factors and thus have produced changes in the normal level. The occupation of the surrounding region by white men has recently modified the face of the land in ways that have a recognized influence on the water level; and the ancient history of the lake includes enormous modifications in response to changes of climate.

"Of human influences the most telling has arisen from the development of agriculture with irrigation. In irrigation the water of rivers and creeks is diverted to cultivated fields, which first absorb it and then through evaporation feed it to the air; and the water thus consumed by utilization is lost to the lake. With the gradual enlargement of the irrigated area the normal level of the lake is inevitably being lowered, and engineers are already confident that the high-water mark of 1877 will never again be reached. On the other hand, there is no reason to expect the lake's extinction, for there is a limit to the possibilities of irrigation.

"The fresh water brought by the rivers mingles gradually with the brine, and as the river mouths are on or near the eastern shore the brine is not so strong at the east as at the west. Analyses of samples of the brine gathered at different points and in different years report the dissolved solids as from 13.7 to 27.7 per cent by weight. A sample taken in August, 1914, contained 18.9 per cent of solids. At the present time the average salinity of the lake is about 5-1/2 times that of the ocean, and its density is 14.5 per cent greater than that of fresh water. * * *

"The brine is weakest in the northeastern arm. * * * This arm has been partitioned from the main body by the embankment of the Southern Pacific Co. and is continuously supplied with fresh water by Bear River. Ice can form on the stronger brine only in zero weather, but this arm is frozen from side to side every winter, and sleighs have been driven across it.

"The only climatic element with which the lake oscillations have been connected by direct observation is precipitation—the lake rises or sinks as the fall of rain and snow is great or small—but it is easy to understand that the balance between supply and loss of water may also be disturbed by any change of climate which affects the rate of evaporation. As every laundress well knows, evaporation is favored by heat, by dryness of the air, and by strength of wind and is retarded by cold, by moisture in the air, and by calm. So there are at least four ways in which changes of climate may cause the lake to expand or contract. * * *

"The only permanent animal inhabitant of Great Salt Lake is a tiny 'brine shrimp,' a third of an inch in length. A more conspicuous temporary resident is a minute fly, which passes its larval stage in the water and when its transformation takes place leaves behind it the discarded skin. These flies are so numerous in their season that even the passing tourist should feel grateful that they do not bite. Their brown exuviae darken the water edge and often sully broad belts of the lake surface. More decorative denizens are gulls and pelicans, which find safe nesting ground on some of the smaller islands. There are no shoal-water plants, and the salt spray of the beach is fatal to all land vegetation along the shores.

"When the lake is low its salt is segregated and deposited in shallow lagoons at its margin, to be redissolved when the water rises. Each autumn, as the water cools, deposits of hydrated sodium sulphate (Glauber's salt) coat piles and other fixed objects near the water surface, and the deposits increase as the temperature falls. * * * Calcium carbonate—the mineral constituting limestone, travertine, and chalk—is continuously and permanently separated from the water, which is unable to retain that which is brought to it by the rivers. Along the shores it forms minute balls, which together constitute sand, a sand quite distinct from the siliceous sand of ordinary beaches.

"Man makes little use of the lake. On its shores there are neither fisheries nor ports, and commerce finds it an impediment rather than an aid. Its deposits of Glauber's salts, which it offers for the gathering, are neglected because the world's demand is small and is cheaply met in other ways. Its common salt is harvested with great economy of effort, for impurities are easily excluded, and the work of evaporation is performed by the sun. The present annual output of 40,000 tons must be multiplied fivefold before it can commence to weaken the brine. For the rest, man is content to resort to its shore for bathing and to realize a new sensation as he floats upon its surface."

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Last Updated: 16-Feb-2007