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.
Anding District, which means "peaceful and stable", belongs to Dingxi City, Gansu Province. It is the seat of Dingxi Municipal Party Committee and Municipal Government. It is located in the central part of Gansu Province. It is 82.9km long from north to south and 73.3km wide from east to west, with a total area of 4225 square kilometers. The region has jurisdiction over 12 towns, 7 townships and 3 subdistrict offices, with a resident population of 430500 at the end of 2017. Anding District was built in 1096 AD (the second year of Shaosheng in the Northern Song Dynasty), named "Dingxizhai", and Dingxi County was founded in 1142 (the second year of Jin Huangtong). In September 2003, Dingxi County withdrew its county and set up a district, which was renamed as "Anding District of Dingxi City". Anding District is one of the birthplaces of the Yellow River civilization, the important town of the ancient "Silk Road" and the necessary place for the New Eurasian Continental Bridge. It is known as "Gansu throat and Lanzhou Gateway", which is far away from the provincial capital Lanzhou.