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.
Dongxing District, which belongs to Neijiang City, Sichuan Province, is located in the central and southern part of Sichuan Basin and on the east bank of the middle reaches of the Tuojiang River. Dongxing District is bordered by Rongchang District to the east, Daan District and Longchang City to the south, Shizhong District to the west, and Zizhong County and Anyue County to the north. Chengdu-Chongqing Railway, Guangzhou-Chengdu Highway (National Highway 321) and Xiamen-Rong Expressway (G76) cross the border, 153km from Chengdu and 146km from Chongqing, with a total area of 1180.58 square kilometers. Dongxing District was once known as the "Sweet City" because of its rich sugar cane and developed sugar industry, and also known as the "hometown of calligraphy and painting" because of the emergence of the eldest son of Gongsun, the master of traditional Chinese painting Zhang Daqian, Zhang Shanzi, and the "news magnate" Fan Changjiang. At the end of 2019, Dongxing District has jurisdiction over 5 streets and 14 towns.