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.
Ningxian County, which belongs to Qingyang City, Gansu Province, is located in the eastern part of Gansu Province, between longitude 107o41'to 108o34cm east, latitude 35o15' to 35o52' north, Ziwuling in the east, Jinghe and Shaanxi Province in the south, Heshui County in the northwest, Xifeng District and Zhengning County in the southeast, and the Malian River passing through the county from north to south. It is the main river of Ningxian County, with a total area of 2633 square kilometers. As of 2014, Ningxian County has jurisdiction over 14 towns, 4 townships, 257 administrative villages and 13 communities, with a total population of 556100. In 2012, the county achieved a regional gross domestic product (GDP) of 4.714 billion yuan, a year-on-year increase of 21.0% in terms of comparable prices. Ningxian County has Xiangle Song Pagoda, Puzhao Temple Zhenyuan Bell, Ta'erzhuang five dynasties Pagoda, Wang Xiaoxi Martyrs Memorial Hall and so on.