Great Salt Lake is located in the northern part of the U.S. state of Utah. It is the largest salt lake in the Western Hemisphere, the fourth largest terminal lake in the world and the 33rd largest lake on Earth. In an average year the lake covers an area of around 1,700 square miles (4,400 km²), but the lake's size fluctuates substantially due to its shallowness. For instance, in 1963 it reached its lowest recorded level at 950 square miles (1,529 km²), but in 1987 the surface area was at the historic high of 3,300 square miles (5,311 km²).
It has a length of 75 miles and a maximum width of 28 miles. Its average depth is 14 feet deep with the maximum depth being 33 feet deep.
The lake is the largest remnant of Lake Bonneville, a pluvial lake which covered much of western Utah in prehistoric times. Great Salt Lake is endorheic (has no outlet besides evaporation), and therefore has very high salinity, far saltier than sea water. The Jordan, Weber and Bear rivers (the three major tributaries) deposit around 1.1 million tons of minerals in the lake each year and the balance of evaporated water is mineral-free, concentrating the lake further.
Because of its unusually high salt concentration, most people can easily float in the lake as a result of the higher density of the water, particularly in the saltier north arm of the lake, Gunnison Bay. The lake's shallow, warm waters cause frequent, sometimes heavy lake-effect snows during late fall, early winter and spring.
Although it has been called "America's Dead Sea", the lake provides habitat for millions of native birds, brine shrimp, shorebirds and waterfowl, including the largest staging population of Wilson's Phalarope in the world.
Great Salt Lake is a remnant of a much larger prehistoric lake called Lake Bonneville which, at its peak surface area, was nearly as large as Lake Michigan and significantly deeper, covering roughly ten times the area of Great Salt Lake and over 1,000 feet (305 metres) deep. It covered much of present-day Utah and small portions of Idaho and Nevada during the Pleistocene Epoch, more commonly known as the Great Ice Age, between 32,000 and 14,000 years ago. With the change in climate, the lake began drying up, leaving Great Salt Lake, Utah Lake, Sevier Lake, Rush Lake and Little Salt Lake as remnants.
Due to the warm waters of the Great Salt Lake, lake-effect snow is a frequent phenomenon of the lake. Cold north, northwest or west winds generally blow across the lake following the passage of a cold front, and the temperature difference between the warm lake and the cool air can form clouds that lead to precipitation downwind of the lake.
The lake-effect snows are more likely to occur in late fall, early winter, and during spring due to the higher temperature differences between the lake and the air above it. The water is generally too cold to support lake-effect snow during mid-winter, since the lake temperatures usually fall to near the freezing point. During summer, the temperature differences can form thunderstorms that form over the lake and drift eastward along the northern Wasatch Front. Some rainstorms may also be partially contributed due to the lake-effect in fall and spring. It is estimated that approximately 6-8 lake-effect snowstorms occur in a year, and that 10% of the average precipitation of Salt Lake City can be attributed to the lake-effect.
The high salinity of the lake makes it uninhabitable for all but a few species, including brine shrimp, brine flies, and several forms of algae. The brine flies have an estimated population of over one hundred billion, and serve as the main source of food for many of the birds which migrate to the lake. However, the fresh- and salt-water wetlands along the eastern and northern edges of the Great Salt Lake provide critical habitat for millions of migratory shorebirds and waterfowl in western North America. These marshes account for approximately 75% of the wetlands in Utah. Some of the birds that depend on these marshes include: Wilson's phalarope, red-necked phalarope, American avocet, black-necked stilt, marbled godwit, snowy plover, western sandpiper, long-billed dowitcher, tundra swan, American white pelican, white-faced ibis, California gull, eared grebe, peregrine falcon, bald eagle, plus large populations of various ducks and geese.
There are no fish in the Great Salt Lake because of the high salinity. The only aquatic animals able to live in the lake are tiny brine shrimp (Artemia franciscana).
The lake and its shores contain oolitic sand, which are small, rounded, or spherical grains of sand made up of a nucleus (generally a fecal pellet or a small mineral grain) and concentric layers of calcium carbonate (lime) and look similar to very small pearls.
