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.
Guang'an, a prefecture-level city of Sichuan Province, is located in the eastern part of Sichuan Province, located in the humid monsoon climate area of the middle subtropics, with four distinct seasons, warm climate, abundant rainfall and rich products. Jialing River, Qujiang River zigzag loop into the Yangtze River, Huaying Mountain, Causeway Mountain, Mingyue Mountain parallel distribution in the eastern part of the city; a total area of 6339.22 square kilometers, under the jurisdiction of 2 districts, 3 counties, 1 city; 2017 household registration population of 4.647 million. Guang'an has a long history, and the recorded history of civilization can be traced back to more than 3,000 years ago. Since the second year of Kaibao in the Northern Song Dynasty (969), the meaning of "Guang Tu'an Collection" has been set up by the Guang'an Army, and the name "Guang'an" has continued to this day. Guang'an was established in July 1993 and set up a city in July 1998. Guang'an is the hometown of Comrade Deng Xiaoping, chief architect of China's reform and opening up.