Burro Mesa

Burro Mesa is a gently westward-sloping mesa standing high above the surrounding desert floor to the northwest of the Chisos Mountains in Big Bend National Park, southern Brewster County (at 29°15' N, 103°25' W). At its highest point the mesa reaches an elevation of 4,431 feet above sea level. Its name derives from the many wild burros that once wandered and grazed there. Burro Mesa is the westward down-thrown fault block of the Burro Mesa fault, which runs along the eastern escarpment of the mesa and extends southward into the Burro Mesa fault group, forming one of the major fault zones in this area of the park. The mesa is composed primarily of interbedded tuffs, ash flows, and lavas. These latter two are generally quite resistant, whereas the tuffs are easily eroded. Such a combination often leads to mesa development as erosion proceeds. The hard, igneous rocks crowning Burro Mesa have weathered so much more slowly than the softer rocks on the opposing side of the fault that they have developed over time into a topographic high. The Burro Mesa rhyolite, the prominent member of the south rim formation, caps the upper elevation of the mesa and derives its name from that feature. Vegetation on Burro Mesa is dominated by Chihuahuan Desert scrub, including various shrubs and such semisucculents as lechuguilla, ocotillo, and creosote bush, as well as cacti. The candelilla wax plant may also be found scattered over the slopes.