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.
Dachuan District, under the jurisdiction of Dazhou City, Sichuan Province, is located in the south of the main urban area of Dazhou City, and is located in the connecting zone of parallel ridges and valleys in the east of Sichuan Basin, hilly areas in the middle of the basin and low mountain areas around the basin. The general trend of topography is high in the northwest and low in the southeast, belonging to the mid-subtropical monsoon humid climate type; it has jurisdiction over 2 streets, 29 towns and 25 townships, with a total area of 2245 square kilometers, with a total population of 1.118 million at the end of 2017. Dachuan District has a long history and profound cultural heritage. There are a large number of historical celebrities, such as Chun Shenjun, one of the four princes of the warring States, Sima Yuan Zhen of Tongzhou in the Tang Dynasty, Wei Chengfang of the Ministry of officials in the Ming Dynasty, Tang Zhen, an outstanding thinker in the Qing Dynasty, and so on. Unique location and convenient transportation. Dachuan, as the joint of Sichuan, Chongqing, Hubei and Shaanxi, is located in the radiation center of the four major cities of Chengdu, Chongqing, Xi'an and Wuhan.