Featured in this photograph is the angular southern end of the Guadalupe Mountains of west Texas, the largest fossil reef in the world. Visible are the sheer southeastern slopes; El Capitan [8078 feet (2462 meters)]; and Guadalupe Peak [8751 feet (2667 meters)], the highest elevation in Texas. Within the region are reef rocks of limestone that form peaks in the Guadalupe Mountains, sandstone, and some shoal deposits. Guadalupe Mountains National Park was established in 1972. Arid Salt Basin, made up of numerous dry lakes, lies southwest of the Guadalupe Mountains. Rectangular and circular field patterns (lower right corner) indicate the presence of dryland farming and irrigated agriculture.