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.
Dushan County, which belongs to Qiannan Buyi and Miao Autonomous Prefecture of Guizhou Province, is located at the southernmost tip of Guizhou, bordering Nandan County, Guangxi. It is a necessary place for Guizhou Province and even the southwest to enter the sea mouth of Guangdong and Guangxi. Defending Guangdong and Guangdong in the east, Yunnan and Guizhou in the west, ASEAN in the south and Tianfu in the north, known as "the south gate of Guizhou" and "southwest gate", it is not only an important town in southern Guizhou, but also the opening frontier of the western region connecting the central and eastern regions. Dushan County has a total area of 2442.2 square kilometers. In 2012, the total population of Dushan County was 350000, and the GDP was 3.46173 billion yuan. It has been designated as a Class An open county by the state and a comprehensive reform experimental area in ethnic minority areas, a comprehensive agricultural development county, a collective economic experimental area and a spark technology intensive experimental area by the provincial government. December 2016, listed as the third batch of countries