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.
Chaotian District is the municipal district of Guangyuan City, Sichuan Province, with 25 townships under the jurisdiction of the region, with a total population of 200000, an area of 1620 square kilometers and a cultivated land area of 260000 mu. It is the first political, economic and cultural center at the starting point of Shu Road in the southern foot of the Qinling Mountains. It is known as "the important town of Qin and Shu" and "the gateway to northern Sichuan". According to legend, Emperor Xuanzong of the Tang Dynasty went to Shu to avoid the an-Shi Rebellion. Various states and counties greeted him here, calling it "the son of Heaven", hence the name "Chaotian", which extended to the meaning of "rising to Heaven". Chaotian has always been the government of Lizhou and Guangyuan (prefecture and county). After the founding of New China, it was under the jurisdiction of Guangyuan County. In 1989, with the approval of the State Council, Chaotian District of Guangyuan City was established. On September 25, 2018, he won the honorary title of "2018 e-commerce into rural comprehensive demonstration county" of the Ministry of Commerce. 2019 1