The peculiarities of the two storm lines have an important bearing on the history of the lake. The fact that the belt of land between them supported sage bushes shows that previous to its present submergence the lake had not covered it for many years. Lands washed by the brine of the lake become saturated with salt to such extent that even salt-loving plants cannot live upon them, and it is a familiar fact that the sage (Artemisia sempervirens) never grows in Utah upon soil so saline as to be unfavorable for grain. The rains of many years, and perhaps even of centuries, would be needed to cleanse land abandoned by the lake so that it could sustain the salt-hating bushes, and we cannot avoid the conclusion that the ancient storm line had been for a long period the superior limit of the fluctuations of the lake surface.
To avoid misapprehension, it should be stated that the storm lines have been described as they appear on the eastern shore of Antelope Island, a locality where the slope of the ground amounts to three or four degrees. The circumstances are different at the margin of the mainland, and especially where the slopes are very gentle. The lake is so shallow that its equilibrium is greatly disturbed by strong winds. Its waves are small, but in storms the water is pushed high up on the land toward which the wind blows, the extreme effects being produced where the inclination is most gentle. The islands, however, are little flooded; the water does not accumulate against them, but is driven past; and the easterly gales that produced the present storm line on the east shore of Antelope Island may have driven so much water to the westward as even to have depressed the level in that locality. Moreover, where the land surface is nearly level, the cleansing by rain of portions once submerged is indefinitely retarded. On all the flatter shores the lake is bordered by tracts too saline for reclamation by the farmer, and either bare of vegetation or scantily covered by salt-loving shrubs. These tracts are above the modern storm line, and they acquired their salt during some flood too remote to be considered in this connection. The largest of them is called the Great Salt Lake Desert, and has a greater area than the lake itself.
Thus it appears that in recent times the lake has overstepped a bound to which it had long been subject. Previous to the year 1865, and for a period of indefinite duration, it rose and fell with the limited oscillation and with the annual tide, but was never carried above a certain limiting line. In that year, or the one following, it passed the line, and it has not yet returned. The annual tide and the limited oscillation are continued as before, but the lowest stage of the new regime is higher than the highest stage of the old. The mean stage of the new regime is 7 or 8 feet higher than the mean stage of the old. The mean area of the water surface is a sixth part greater under the new regime than under the old.
The last statement is based on the United States surveys of Captain Stansbury and Mr. King. The former gathered the material for his map in 1850, when the water was at its lowest stage, and the latter in the spring of 1869, when the water was near its highest stage. The one map shows an area of 1,750 and the other of 2,166 square miles. From these I estimate the old mean area at 1,820 miles, the new at 2,125 miles, and the increase at 305 miles, or 17 per cent.
COMPARATIVE MAP OF GREAT SALT LAKE, UTAH COMPILED TO SHOW ITS INCREASE OF AREA
The topography and later shore-line are taken from the Survey of Mr. Clarence King, U.S. Geologist; the earlier shore-line from the Survey of Capt. Howard Stansbury, U.S.A.
The “abnormal change” of the lake may then be described as an infilling or rise of the water whereby its ordinary level has been raised 7 or 8 feet and its ordinary area has been increased a sixth part; and this appears to be distinct from the limited oscillation and annual tide, which may be regarded as comparatively normal. To account for it a number of theories have been proposed, and three of them seem worthy of consideration. They appeal respectively to volcanic, climatic, and human agencies.
VOLCANIC THEORY.
It has been surmised that upheavals of the land, such as sometimes accompany earthquakes, might have changed the form of the lake bed and displaced from some region the water that has overflowed others. This hypothesis acquires a certain plausibility from the fact that the series of uplifts and downthrows by which the mountains of the region were formed have been traced down to a very recent date, but it is negatived by such an array of facts that it cannot be regarded as tenable. In the first place, the water has risen against all the shores and about every island of which we have account. The farmers of the eastern and southern margins have lost pastures and meadows by submergence. At the north, Bear River Bay has advanced several miles upon the land. At the west, a boat has recently sailed a number of miles across tracts that were traversed by Captain Stansbury’s land parties. That officer has described and mapped Strong’s Knob and Stansbury Island as peninsulas, but they have since become islands. Antelope Island is no longer accessible by ford, and Egg Island, the nesting ground of the gulls and pelicans, has become a reef. Springs that supplied Captain Stansbury with fresh water near Promontory Point are now submerged and inaccessible; and other springs have been covered on the shores of Antelope, Stansbury, and Fremont islands.