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.
Zheng'an County is the lower jurisdiction county of Zunyi City, Guizhou Province, which is located in the northeast of Zunyi City. It is the frontier of Chongqing and the important economic and cultural intersection area of southern Chongqing and northern Guizhou. It is known as the "gateway to northern Guizhou". Zheng'an County is located in the north of Guizhou Province, bordering Nanchuan District of Chongqing to the north, Daozhen County and Wuchuan County in the northeast, Fenggang County and Meitan County in the southeast, Suiyang County in the south and Tongzi County in the northwest. In 2017, Zheng'an County achieved a regional GDP of 10.06382 billion yuan, of which the added value of the primary industry was 2.86398 billion yuan, the secondary industry was 2.221 billion yuan, and the tertiary industry was 4.97884 billion yuan. The proportion of the three industrial structures in the gross domestic product is 28.4% in the primary industry, 22.1% in the secondary industry and 22.1% in the tertiary industry.