Gypsum grains form the bright-white dunes that cover about 2,000 acres and range from three feet high, heavily vegetated dunes at the south end of the area, to sixty feet high, largely non-vegetated dunes at the north end. Nearby, dunes consisting of pale red quartz grains are even more common and reach their greatest height, (approximately 33 feet), north of the Patterson Hills (the large hills between the gypsum dunes and the western escarpment).
