Dating back centuries, salt-crusted plains in present-day Oklahoma held great value to native tribes and, later, to homesteaders. People used the inland supply of salt in their diets, for tanning deer hides, and for trade. The area also proved to be a fertile hunting ground due to the abundance of game that sought out the nutrient-rich habitat.
Since 1930, the salty deposit located about 90 miles (150 kilometers) northwest of Oklahoma City has been part of Salt Plains National Wildlife Refuge. Today, the plains are still known as a gathering place for diverse animal life, including more than 300 species of birds. But its salt resources have become appealing in another way: it is the only place in the world where people can dig for a distinctively patterned form of crystallized gypsum.
The OLI (Operational Land Imager) on Landsat 8 captured these images of the area in natural color (above) and false color (below) on October 10, 2025. The salt basin is partially filled by Great Salt Plains Lake, a shallow reservoir formed by the damming of the Salt Fork Arkansas River and fed by ephemeral streams.
The false-color image combines the shortwave infrared portion of the electromagnetic spectrum with visible light (OLI bands 7-4-2). In this combination, healthy vegetation appears dark red to purple, and water is blue. The variation in color on the salt plain may be due to different moisture or salinity levels. (Scientists can use shortwave infrared data in estimations of soil salinity.)
The basin’s salt has its origins in the Permian Period, about 300 million to 250 million years ago. A shallow salt layer from that time still underlies parts of the southwestern U.S., including western Oklahoma. Salt gradually dissolves into groundwater, and when the resulting brine rises to the surface, the water evaporates and leaves behind a bright crust.
The saline water is a key component in a mineral structure unique to the area—hourglass selenite crystals. Selenite, a crystalline variety of gypsum, forms in the top two feet of the wet subsurface when saline water combines with gypsum. The process can occur relatively quickly when temperatures and moisture le …