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.
Nanzheng District, which belongs to Hanzhong City, Shaanxi Province, gets its name because of Zheng people's running south. It is located in the southwest border of Shaanxi Province, southwest of Hanzhong Basin, facing Hanjiang River in the north and Yiba Mountain in the south. The area is adjacent to Chenggu County and Xixiang County in Shaanxi Province in the east, Tongjiang County, Nanjiang County and Wangcang County in Sichuan Province in the south, Ningqiang County and Mian County in Shaanxi Province in the west, and Hantai District in Shaanxi Province across the river in the north, covering an area of 2809.0363 square kilometers. The climate in the territory belongs to the north subtropical zone and the warm temperate zone, especially in the north subtropics. Nanzheng is not only an important part of Hanzhong "double hundred" urban planning, but also an economically developed area of Hanzhong City, which has a world-class Tiankeng group. Nanzheng District is also a large area of tourism resources in Shaanxi Province, with scenic spots such as Nanhu Lake, Hongsi Lake,