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.
Xishui County, a county under the jurisdiction of Huanggang City, Hubei Province, China, is an important part of Wuhan city circle. The total area is 1949.3 square kilometers, with a population of 1.08 million in 2016. Xishui County was formerly known as Qishui County. In order to avoid being confused with the name of Qichun County, the Republic of China was changed to Xishui County in 22 years (1933). Xishui County is located in the southern foot of the Dabie Mountains, eastern Hubei, the north bank of the middle reaches of the Yangtze River, Xishui County is located in the southern foot of the Dabie Mountains, eastern Hubei, the north bank of the middle reaches of the Yangtze River, belonging to Huanggang City. Located in the Yangtze River open development zones of Jiujiang, Huangshi and Wuhan, the Yangtze River waterway, Liujie Highway and Hu-Rong Expressway are in parallel transit; the Huangshi Yangtze River Bridge spans the Xishui River and scattered flowers; and the Beijing-Kowloon Railway runs across the territory and has two passenger and cargo stations, forming a network of railways, highways and waterways extending in all directions. There are 15 counties under the jurisdiction of Xishui county