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.
Jinchuan County, formerly known as Jinhua County, belongs to Aba Prefecture of Sichuan Province, located in the northwest of Sichuan Plateau, southwest of Aba Tibetan and Qiang Autonomous Prefecture, located on the eastern edge of the Qinghai-Tibet Plateau, upstream of the Dadu River, crossing 101 °13 degrees east longitude 102 °19km, 31 °0km north latitude 31 °58km, Jinchuan County covers an area of 5550 square kilometers. Jinchuan has a continental plateau monsoon climate, with sunny weather and a large temperature difference between day and night. It has jurisdiction over 22 townships and 110 administrative villages (communities). The county government is based in Lewu Town. As of 2016, Jinchuan County has a total population of 72400, with 80% of the agricultural population and 75% of the minority population. Sui Dynasty, Jinchuan County, Tang Dynasty, Jinchuan Prefecture, Qing Dynasty, Qianlong 14 years (1749), changed soil to flow, set up village governance, 1936