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.
Dongpo District, known as Meizhou in ancient times, also known as Qitong, is the municipal district of Meishan City, located in the middle of Meishan City. In 2013, the total population was 860000, covering an area of 1331 square kilometers, with jurisdiction over 3 streets and 13 towns. Dongpo District is the hometown of navel oranges, high-quality rice and kimchi in China. It is the hometown of famous writers Su Xun, Su Shi and Su Zhe. Dongpo District occupies three of the eight masters of the Tang and Song dynasties. Dongpo District is located at the southwest edge of Chengdu Plain, located in the middle reaches of Minjiang River, 67 kilometers north of Chengdu, 50 kilometers from Shuangliu International Airport and 60 kilometers south to Leshan and Emei Mountain. It is the political, economic and cultural center of Meishan City. In October 2018, it was selected as the "Top 100 areas with National Investment potential in 2018" and the Top 100 areas with New urbanization quality in 2018. October 2019