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.
Xiaonan District is a county-level administrative district under the jurisdiction of Xiaogan City. Xiaonan District is located in the north of Jianghan Plain, adjacent to Wuhan, is the traffic road to the northwest and northeast of Hubei, is an important part of the Yangtze River economic development belt. The whole area is 1020 square kilometers. The total population in 2016 is 1.07 million. The district people's government is stationed in the academy street. Area code: 0712. The district has jurisdiction over 8 towns, 4 streets, 3 townships and 3 games. In April 1993, with the approval of the State Council, the former Xiaogan area was abolished, Xiaogan City at the prefecture level was established, Xiaogan City at the county level was abolished, and Xiaonan District was established. Xiaonan is the legendary place where the "seven fairies" came down to earth. Since the first year of Song Xiaowu in the Southern Dynasty (AD 454), it has been the seat of counties, states, governments, departments and cities. Xiaonan is rich in cotton, oil, livestock, eggs, melons and fruits, which is a national commodity.