Salt Flats, Utah

In northwestern Utah outside of Salt Lake City 110 miles, are the Bonneville Salt Flats – a densely packed salt pan, about 12 miles long, 5 miles wide covering approximately 46 square miles. The formation of the Salt Flats began at the end of the last Ice Age when the waters of ancient Lake Bonneville began to recede. In the area of the salt flats, this freshwater lake was almost 1000 feet deep and covered 1/3 of Utah! Near the center of the salt, the crust is almost 5 feet thick in places, with the depth tapering off to less than 1 inch as you get to the edges. Total salt crust volume has been estimated at 147 million tons or 99 million cubic yards of salt.

Over decades, the lake slowly disappeared, leaving large concentrations of dissolved minerals deposited in the soils that formed the watershed for the Bonneville Salt Flats. Approximately 90% of the area is halite (common table salt), along with large concentrations of gypsum (commercially used to make household drywall) and smaller quantities of potassium and magnesium.

Today, groundwater slowly flows towards the Salt Flats from the surrounding watershed, picks up dissolved minerals along the way, and percolates up to the surface via a shallow brine aquifer. 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 the groundwater floods the Salt Flats several inches deep. Wind, p rainstorms, and regional climate also play an important part in changing salt crust conditions throughout each year.

Entrance is free and open to the public most of the year. The area has special events (like Speedracing, endurance runs, rocket clubs) so be aware it may be closed during these times.

Driving is permitted on the flats, although there are sometimes seasonal closures when the salt is moist or there’s standing water on the surface — signs will be posted- Drive at your own risk. There are no services, restaurants, no cell phone coverage, no overnight camping. Visitors should only venture beyond the road when the flats are completely dry. To get there, take Exit 4 off Interstate 80 approximately 110 miles west of Salt Lake City. Head north and follow the signs to the Speedway-there is a parking area at the end of the road. Visitors should only venture beyond the road when the flats are completely dry. The edges of the flats are significantly thinner than other sections, and driving near them can result in getting stuck in thick mud.

History

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 a fur trading company run by Captain Benjamin L. E. Bonneville.

In 1845 in an effort to find a shorter route to the Pacific, John C. Fremont and his exploratory expedition crossed through the heart of the Salt flats. His route would come to be known as the Hastings Cutoff route along the California Trail and he promoted it to be faster and easier route to California.

However, the Hastings Cuttoff proved to be just the opposite for the Donner party of 1846 who tragically froze to death in the California Sierra Mountains near Donner, CA. 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 bogged in the mud found just below the thin salt crust. Abandoned wagon parts from the party were present on the flats well into the 1930s, and the wheel tracks from their wagons are still visible today at certain points along the trail. Today, it is part of the federally protected California National Historic Trail.