deflected upwards, penetrating the overlying rock strata and forming a salt dome. The salt may not have actually been exposed on the surface, but groundwater entering the top of the dome dissolved the underlying salt beds, allowing the center to collapse, forming what is today Paradox Valley. This process took place over about 150 million years, a long enough time for the Dolores River to downcut into the land and maintain its ancient course. The same process also created the Moab Valley (Spanish Valley) to the west, itself cut crosswise in a similar fashion by the Colorado River. The Paradox Formation, a geological formation containing salt, gypsum, anhydrite, shale, sandstone, and limestone, is named after exposures found in Paradox Valley. The Paradox Basin, a geologic province throughout which the Paradox Formation is found, also bears the name of the valley. History Paradox Valley was within the historical domain of the Ute tribe. An 1868 treaty created a reservation for the Utes over much of western Colorado, including Paradox Valley. Squatters began grazing cattle in the valley as early as 1877, in violation of the treaty. By 1881, the Utes had been forced out of the area, and in 1882 the United States Congress officially opened the land to settlement. Springs and streams allowed farming in the northwest end of the valley, and the mid-1890s discovery of copper at the future site of the Cashin Mine near the town of Bedrock brought in a further influx of settlers. The valley and the surrounding plateau would soon become an important source of radioactive materials, including radium and uranium. In 1913, the New York Times identified carnotite mines near Paradox Valley as the source of "the greatest radium ore deposits in the world". Production of radium ceased in 1922 when richer deposits were found in the Belgian Congo, but production of uranium and vanadium continued throughout most of the century. Paradox Valley Unit Near-surface salt beds up to thick still underlie Paradox Valley. The Dolores River, a tributary of the Colorado River, naturally picks up about 100,000-200,000 tons of salt annually on its way through the valley. In the 1980s, the United States Bureau of Reclamation began construction of a pumping facility known as the Paradox Valley Unit. The PVU, a part of the wider Colorado River Basin Salinity Control Project, became fully operational in 1996 and collects saline groundwater from 12 shallow