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.
Yingjing County, which belongs to Ya'an City, Sichuan Province, is located on the western edge of Sichuan Basin, in the hinterland of Ya'an City, Yucheng District of Ya'an City in the northeast, Hongya County in the southeast, Hanyuan County in the southwest, Luding County in the west, and Tianquan County in the north, 61 kilometers from east to west and 53 kilometers from north to south. The geographical location of Yingjing County is between latitude 29 °29 "29 °56" north and longitude 102 °20 "102 °56 'east. In 2015, Yingjing County covers an area of 1781.04 square kilometers and has jurisdiction over 3 towns and 18 townships. It is a subtropical monsoon climate with mild climate, four distinct seasons and abundant rainfall, with an average annual temperature of 15.2℃, an average annual sunshine of 886.6 hours and an average annual rainfall of 1133.1 mm. The county government is stationed at No. 1 Xiangyang Lane, Yandao Town. There are 17 ethnic minorities living in Yingjing County.