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.
Danling County, which belongs to Meishan City, Sichuan Province, is located on the southwest edge of Chengdu Plain in Sichuan Basin, in Chengdu Economic Zone and Chengdu-Chongqing Economic Zone. Danling County covers an area of 448.94 square kilometers in 2011, with a total population of 163000, and has jurisdiction over 5 towns and 2 townships. The four seasons are mild, with a monsoon climate in the subtropical humid zone, with an annual average temperature of 17.0 ℃ and a forest coverage of 46.2%. It is known as "the hometown of Chinese folk art (suona)". In 2013, GDP in Danling County reached 4.09 billion yuan, an increase of 10.4% over the same period in 2012. The fiscal revenue was 223 million yuan, an increase of 31.2% over the same period in 2012. The per capita net income of farmers was 9519 yuan, an increase of 14.2% over the same period in 2012. On October 22, 2018, Danling County was selected for 2018.