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.
Jinchang, a prefecture-level city under the jurisdiction of Gansu Province, is high in the south and low in the north, with mountains crisscross with flat rivers and Gobi oases, with a continental temperate arid climate, sufficient light and dry climate; it has jurisdiction over Jinchuan District and Yongchang County, with a total area of 9593 square kilometers; and the resident population is 469200 in 2017. Jinchang, located in the middle of Hexi Corridor, is an important node city of ancient Silk Road and one of the major cities of Hexi Corridor. Since ancient times, its natural conditions have been relatively harsh. Jinchang is one of the 110 key water-deficient cities and 13 resource-based water-deficient cities in China. It is also an area with fragile natural ecological environment in western China. Jinchang edge mining enterprise, because of the establishment of the city, because of the rich nickel is known as "the nickel capital of the motherland". In 2011, he won the title of "National Health City". In January 2014, the Ministry of Urban and Rural Construction ordered it.