What are the Bonneville Salt Flats?
Covering over 30,000 acres or 45 square miles, the Bonneville Salt Flats are a unique resource administered by the Bureau of Land Management as an Area of Critical Environmental Concern (ACEC) and Special Recreation Management Area (SRMA). Thousands of visitors, commercial film makers, and land speed racers make the Bonneville Salt Flats a world famous destination.
How did the area get its name?
The area is named for Captain Benjamin L. E. Bonneville, a French-born U.S. Army officer on furlow who ran a fur trading company in the Rocky Mountains in the 1830s. In 1833, trapper, trader, explorer, and legendary frontiersman Joseph R. Walker mapped and explored the area around the Great Salt Lake and crossed the northern perimeter of the Salt Flats while working for the company run by Captain Bonneville. In those days, it was common for fur trappers to name significant landmarks after their employers, perhaps in an effort to gain favor or better wages. It is from Benjamin Bonneville that the salt slats and ancient lake derive their name, although there is no historical record to show that Bonneville himself ever saw the area that bears his name.
What is the history of the area?
Before Joe Walker, fellow trapper and frontier explorer Jedediah Smith was perhaps the first white man to cross the salt flats in 1827 while returning from his first expedition to California. Before then, Native Americans throughout the region were familiar with the desert region west of the Great Salt Lake and informed white explorers of what was there. In 1845, John C. Fremont and his U.S. government-sponsored exploratory expedition crossed through the very heart of the salt flats in an effort to find a shorter overland route to the Pacific. In the following year, Fremont's route across the flats would come to be known as the Hastings Cutoff route along the California Trail.
Promoted by Lansford Hastings as a faster and easier route to California, the Hastings Cuttoff proved to be just the opposite for the ill-fated Donner-Reed party of 1846. A factor contributing to the Donner-Reed tragedy in the Sierra Nevadas was the delay the party experienced on the salt flats when their wagons became mired in the mud found just below the thin salt crust. The tragedy of the Donner-Reed Party limited extensive use of the Hastings Cutoff as an overland migration trail. However, today it is part of the federally protected California National Historic Trail.
How are the salt flats formed?
In the arid environment of Utah's West Desert, many people are surprised the answer involves water. During the last Ice Age over 12,000 years ago, ancient Lake Bonneville was the size of Lake Michigan. It covered one-third of present-day Utah and parts of neighboring states. You can see traces of the shorelines, representing different levels of the receding lake, etched into the mountains throughout Utah. The Bonneville Salt Flats and the Great Salt Lake are remnants of ancient Lake Bonneville. When the waters receded at the end of the last Ice Age, large concentrations of dissolved minerals were deposited in surrounding soils. These minerals include gypsum (commercially used to make household wallboard) and halite (common table salt). The Bonneville Salt Flats are comprised of approximately 90% salt.
Today, ground water flows from the surrounding area, picks up dissolved minerals along the way, and percolates up to the surface of the flats. When temperatures rise in the late spring and summer months, the salty water rapidly evaporates in the heat and the minerals are left behind to form the salt crust. During the cooler months of the year (November to May), evaporation slows down and ground water floods the salt flats several inches deep. Wind, periodic rainstorms, and regional climate also play an important part in changing salt crust conditions throughout each year. The stratified layers that form the salt flats are almost 5 feet thick near the center. The total measured volume of the Bonneville Salt Flats equals 147 million tons or 99 million cubic yards of salt!
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