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.
Hua'an County (ancient Zhangzhou capital Longxi County) is located in the south of Fujian Province, northwest of Zhangzhou City, the middle reaches of the North Stream of the Jiulong River, known as & quot; North Stream Pearl-quot;. Adjacent to Zhangping, Anxi, Changtai, Yancheng, Nanjing. 150 kilometers away from Xiamen, it is one of the coastal open counties in Fujian Province. it is also the county with the largest concentration of Alpine compatriots in the mainland of the motherland. it is the largest forestry commodity production base in southern Fujian and a key forestry county in Fujian Province. Speak Hokkienese. Hua'an belongs to the "former Central Soviet area County". It is a world cultural heritage site, a national forest park, a national ecological construction demonstration county, a national key tea-producing county, a national tea characteristic county, a hometown of famous tea in China, a county with advanced scientific and technological progress, a county with advanced scientific and technological work, and a hometown of Pingshan pomelo in China.