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.
Zigong, a prefecture-level city of Sichuan Province, is located in the south of Sichuan Basin; Longchang City and Lu County to the east, Luzhou City and Yibin City to the south, Jianwei County and Jingyan County to the west, Renshou County, Weiyuan County and Neijiang City to the north; geotectonic system Yangzihuai Sichuan Taiao, Chuanzhong Taigong and Zigong sag; it belongs to subtropical humid monsoon climate; in 2017, the city covers an area of 4381 square kilometers and has jurisdiction over 4 districts and 2 counties. The registered population is 3.2394 million. Zigong "set up a city due to salt", and the words "Zi and Gong" are derived from the names of "Ziliujing" and "Gongjing". At the same time, Zigong is also an important producing area of dinosaur fossils in China, known as the "hometown of dinosaurs". It is famous at home and abroad for the Zigong Dinosaur Museum, which is one of the three dinosaur museums in the world. Zigong gourmet salt is