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.
Xianning, a prefecture-level city in Hubei Province, is located in the southeast of Hubei Province, on the south bank of the middle reaches of the Yangtze River, bordering Hunan and Jiangxi. Known as "the south gate of Hubei", it is an important member of the Wuhan urban circle and the urban agglomeration in the middle reaches of the Yangtze River; mild climate, abundant precipitation, sufficient sunshine, four distinct seasons, long frost-free period; the terrain is high in the south and low in the north; under its jurisdiction: Xianan District, Tongcheng County, Tongshan County, Jiayu County, Chongyang County, Chibi City. The total population in 2017 is 2.5351 million. Xianning has won the China Human settlement Environment Model Award, the most suitable human settlement city in China, the charming city in China, the hot spring city in China, the ten most growing and innovative cities in China, and the second batch of renewable energy building application demonstration cities in China. Hubei Province, the first batch of low-carbon economy pilot cities, the first batch of national tourism standardization cities, national forest cities.