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.
Dejiang County, which belongs to Tongren City, Guizhou Province, is located in the northeast of Guizhou Plateau, at the confluence of Wuling Mountain and Dalou Mountain. It is adjacent to the Yinjiang River to the east, Sinan to the south, Fenggang to the west, and Yanhe and Wuchuan to the north. It covers an area of 2072 square kilometers and has jurisdiction over 3 streets, 12 towns, 8 townships and 345 villages with a total population of 540000 (2012). Dejiang County, 334 kilometers away from the provincial capital Guiyang and 220 kilometers from Tongren City, is known as "the hometown of Nuo Opera, Tianma and Qishi". It has the ruins of Fuyang County in the Sui and Tang dynasties, Fengxiangxi Conference Monument and other scenic spots. On February 2, 2019, it was rated as a county-level national advanced unit of traditional Chinese medicine by the State Administration of traditional Chinese Medicine. In March 2019, it was selected into the list of the first batch of revolutionary cultural relics protection and utilization districts and counties. twenty