The Colorado Plateau east of Holbrook is underlain by a potash deposit estimated by the AZGS to contain between 682 million and 2.27 billion metric tons of the mineral. This map shows contours of the estimated thickness of the potash-bearing layers in the subsurface, as well as the locations of permitted wells in the area. The deposit underlies lands that include private, State Trust, Tribal, and National Park holdings. In 2004 the Petrified Forest Expansion Act added 125,000 acres to the Park. However, much of that land remains privately owned.