BLACK RIDGE. Black Ridge is southwest of Agua Fria Mountain and twelve miles north-northwest of Terlingua in southwestern Brewster County (at 29°29' N, 103°41' W). It runs from the northwest to the southeast for two miles and includes at least three points higher than 3,950 feet above sea level. The highest point on the ridge, near its southeastern end, is 4,025 feet above sea level and rises more than 400 feet above the surrounding Chihuahuan Desert floor. The relatively less resistant sedimentary rocks around the mafic ridge have eroded away, leaving the harder rock exposed. Mafic rocks are generally dark-colored. Black Ridge supports sparse vegetation characteristic of Chihuahuan Desert scrub, including scattered semisucculents such as lechuguilla, sotol, and yucca, and various shrubs such as creosote bush and ocotillo.
Ross A. Maxwell, The Big Bend of the Rio Grande (Bureau of Economic Geology, University of Texas at Austin, 1968). W. N. McAnulty, "Geology of Cathedral Mountain Quadrangle, Brewster County, Texas," Bulletin of the Geological Society of America 66 (1955). A. Michael Powell, "Vegetation of Trans-Pecos Texas," in New Mexico Geological Society Guidebook (Socorro, New Mexico: New Mexico Geological Society, 1980).