A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Yaozhou District, which belongs to Tongchuan City, Shaanxi Province, is located on the southern edge of the Weibei Plateau in central Shaanxi, southwest of Tongchuan City, Xunyi County in the north, Sanyuan County in the south, Wangyi District and Yintai District in Tongchuan City in the northeast, Fuping County in the southeast and Chunhua County in the southwest. It is between 10834 miles east longitude and 109 degrees 06 east longitude and 34 degrees 48 miles north latitude and 35 degrees 19 degrees north latitude, with a total area of 1617 square kilometers. Yaozhou District, known as Yaoxian in ancient times, is the natural gateway from Guanzhong to northern Shaanxi, known as "Beishan lock key" and "Guanfu lapel throat". Yaozhou has a long history and profound cultural heritage. It used to be the ruler of Kangshi in ancient times, with a history of more than 2160 years. It was Sun Simiao, a medical scientist in the Sui and Tang dynasties, Fu Xuan, a philosopher in the Western Jin Dynasty, Liu Gongquan, a calligrapher in the Tang Dynasty, Linghu Deyi, a historian, and a landscape painter in the Northern Song Dynasty.