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.
Tongzi County is under the jurisdiction of Zunyi City, Guizhou Province. It is located in the north of Guizhou Province, bordering Chongqing in the north, Huichuan District and Renhuai City in the south, Xishui County and Qijiang District in Chongqing in the west, and Nanchuan District and Wansheng District in the north. The ground spans 27 °57 °N 28 °54 °N, 106 °26 °E and 107 °17 °E, with a total land area of 3202 square kilometers. Tongzi County has jurisdiction over 2 streets, 20 towns, 2 townships and 1 ethnic township. At the end of 2017, the registered population of Tongzi County was 742300. Tongzi County is "the hometown of bamboo shoots in China", known as "the gateway to northern Guizhou" and "the key to Sichuan and Guizhou". Sichuan-Guizhou Railway, National Highway 210 and Yu-Zhan Expressway run through the county, and the driving time from the county seat to Guiyang and Chongqing is about 2 hours. In September 2018, Tongzi County withdrew from the poverty-stricken county.