Cerro Castellan, less commonly known as Castolon Peak or Castellan Peak, is a prominent conical mountain rising from the desert floor about a mile northeast of the Castolon ranger station in Big Bend National Park, Brewster County (at 29°09' N, 103°30' W). The mountain is part of a series of summits once known as the Carazones Peaks. Cerro Castellan's peak reaches an elevation of 3,293 feet above sea level, and rises more than 1,000 feet above the terrain below. The geologic origin of the peak, like that of so many other topographic highs in this region of West Texas, is differential erosion-a resistant rock wearing away more slowly than rocks around it. Cerro Castellan is a high stack of volcanic rocks, including ash, lava, and tuffaceous rocks. It is capped by a dense lava flow underlain by various tuffs and basalts. A northwest-trending fault cuts the eastern flank of Cerro Castellan. Though little vegetation grows on the sheer cliffs and steep, pointed profile of its peak, the lower slopes of Cerro Castellan support a sparse growth of Chihuahuan Desert scrub, including most prominently such characteristic species as creosote bush and ocotillo. The name Cerro Castellan seems to mean "castle-warden's hill," though the reasons for this name's adoption are obscure.