Great Salt Lake
Centuries ago Utah's northwestern quarter was covered by Lake Bonneville, a freshwater lake 10 times the size of Great Salt Lake. Covering more than 20,000 square miles in Utah, Nevada and Idaho, this body of water was 900 feet deep at the site of present-day Salt Lake City.
The weight of the water was so great that the Earth's crust in the middle of the basin was depressed more than 150 feet, leaving a shoreline that is still visible. Because of climate change and a volcanic diversion of contributing streams, the huge lake fell below its lowest outlet and shrank to what is now known as Great Salt Lake. Salinity levels vary from 15 to 25 percent (at least six times saltier than the planet's oceans), a salt content that can only be tolerated by blue-green algae and brine shrimp.
The lake owes its extreme saltiness to mineral-laden freshwater streams that feed into it with no outlet. Evaporation of the streams' waters leaves so much salt behind that the lake will buoy a human body. Water trapped in open, diked lakes near the shoreline of Great Sale Lake leaves inches of almost pure salt that is harvested annually for commercial purposes.
On the north side of the lake at Promontory Summit, Golden Spike National Historic Site commemorates the spot where the first transcontinental railroad linked the east and west coasts in 1869. In the lake itself is Antelope Island State Park, where visitors can float effortlessly as well as take advantage of the park's recreational activities.
Great Salt Lake State Park, 16 miles west of Salt Lake City off I-80 exit 104, provides access to the south shore of the lake. The park's marina is a good spot for watching the sun set over the lake. For additional information phone (801) 250-1898.
West of the lake, Great Salt Lake Desert, part of the bed of extinct Lake Bonneville, is composed of silt washed into the huge lake over many years. Highways crossing this desert follow trails blazed by early Mormon settlers. On the western edge of the Great Salt Lake basin lie the Bonneville Salt Flats. Covering about 46 square miles, this expanse of hard, white salt crust has been popular with racing enthusiasts since the 1930s. Many land speed racing records have been set at Bonneville Speedway, a designated area for various motor sports events. Speed Week, held in late August, attracts dedicated gearheads.
For additional information contact the Salt Lake Field Office of the Bureau of Land Management at (801) 977-4300.