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.
Dangchang County belongs to Longnan City, Gansu Province, located in the south of Gansu Province, northwest of Longnan City. Dangchang as a place name began in the Dangchang State established by Liang Qin in the Eastern Jin Dynasty, and changed to Dangzhou in the early Sui Dynasty. Since then, the organizational system has undergone many changes, and Dangchang County was officially established in 1954. Dangchang County has jurisdiction over 11 towns, 14 townships and 336 administrative villages, with a total area of 3331 square kilometers, a total population of 310400 and a resident population of 278700 (2017). Dangchang County is located in the crisscross zone between the Minshan Mountain system and the West Qinling Mountains on the edge of the Qinghai-Tibet Plateau, with an elevation of 1138-4154 meters above sea level, with a temperate continental climate, mild and humid climate, significant vertical climate, and great differences between the north and the south. Natural resources mainly include mineral resources, animal and plant resources, hydropower resources and so on. In 2017, Dangchang County completed production.