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.
Baota District, known as Yanzhou in ancient times, is located in the northern Shaanxi Province and the hilly and gully region of the Loess Plateau in northern Shaanxi. It is known as "Qin important area" and "plugged throat". The Xia Dynasty belonged to Yongzhou, it was successively under the jurisdiction of Di, Jin, Wei and Qin in the Spring and Autumn and warring States period, and it was established in the Han Dynasty, Yanzhou or Yan'an House in the Sui and Tang dynasties, and Fushi after the Song Dynasty. After the Republic of China, it was renamed Yan'an County. In 1937, the Central Committee of the Communist Party of China entered Yan'an and established Yan'an City, which is the seat of the government of the Shaanxi-Gansu-Ningxia Border region. In December 1996, Yan'an withdrew to set up the city, and Yan'an was renamed Baota District. It is the seat of the Yan'an Municipal Party Committee and Municipal Government, and it is the central city of Yan'an. The total land area of the region is 3556 square kilometers, with a registered population of 481200 (2017) and a resident population of 491800 (2017). It has jurisdiction over 9 towns, 4 townships and 5 cities.