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.
Jingyan County, which belongs to Leshan City, Sichuan Province, is located in the southwest of Sichuan Basin, between longitude 102 °55 "104 °00" east and latitude 28 °25 "29 °55 'north, with a total area of 840.6 square kilometers. Jingyan County belongs to the humid climate area of the middle subtropics of Sichuan Basin, with warm and humid climate, the same season of rain, abundant rainfall, but uneven distribution, no severe cold in winter, no heat in summer, slight lack of sunshine, four distinct hot and cold seasons, and two distinct dry and wet seasons. As of 2018, Jingyan County has jurisdiction over 27 townships with a population of about 396500. Jingyan County in ancient times for the field of Shu, Han home Wuyang County Jingyan Town, Sui Kaihuang 11 years (591) Li Longshan County, waste Puting home Jingyan County. From the eleventh year of Emperor Kaihuang of the Sui Dynasty (591) to the founding of the county, more than 600 from the Tang and Song dynasties to the early Yuan Dynasty