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.
Jin'an District, a municipal district of Lu'an City, was established in September 1999. It belongs to the main urban area of Lu'an City. It is not only the political, economic and cultural center of Lu'an City, but also an important part of the national Wanjiang City Belt Industrial transfer demonstration Zone and Hefei Economic Circle. Jin'an District is located in the east of Lu'an City, the provincial capital Hefei in the east, Shou County in the north, Shucheng County in the south and Yu'an District in the west. The famous and special products of Jin'an District are mainly Liuangua tablets, Wanxi White Goose, Yipinzhai brush and so on; the scenic spots are mainly West Anhui Rift Valley, Maotanchang Old Street, Dongtian Lake and so on. As of 2011, Jin'an District covers an area of 1657 square kilometers and has jurisdiction over 5 streets, 11 towns and 6 townships with a total population of 851993. In March 2019, it was on the list of the first batch of revolutionary cultural relics protection and utilization districts and counties. April 29, 2019