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.
Cangyuan WA Autonomous County, which belongs to Lincang City, Yunnan Province, is located between 98 °52 degrees east longitude and 23 °40 degrees north latitude. Cangyuan is commonly known as A WA Mountain area, also known as "Hulu King Land". In April 1949, the WA armed forces in Cangyuan, under the leadership of Communist Party of China, established the Provisional people's Government of Cangyuan County, and established Cangyuan WA Autonomous County in 1964, which is the only old revolutionary base county in Lincang City. 2010 the county has jurisdiction over 6 townships, 4 towns, 93 village committees and one state-run Meng province farm, with a total population of 180000, with ethnic minorities accounting for 93.4%. The WA population accounts for 85.1% of the total population and more than 40% of the WA population in China. It is a border nationality with the WA nationality as the main body and more than 20 ethnic groups such as Dai, Han, Lahu and Yi.