Sierra Madera crater in West Texas is a large, eroded complex impact structure near Fort Stockton, distinguished by a prominent central uplift called Sierra Madera or Madera Mountain that rises 793 feet above the surrounding land. About 8 miles across at its obvious outer rim, with evidence it may originally have been larger, the crater deformed rock layers from the upper Paleozoic to the Cretaceous through intense folding, faulting, brecciation, and uplift. First mapped in 1930 and later confirmed as an impact site in the 1960s through shatter cones, shocked quartz, and geophysical surveys, it also served Apollo-era astrogeology research and astronaut training in 1972.