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.
Bengbu, referred to as clam, also known as Pearl City, is a prefecture-level city in Anhui Province, an important comprehensive industrial base in Anhui Province, located in the north of Anhui Province, the middle reaches of the Huaihe River, with a total area of 5950.72 square kilometers. The registered population is 3.8125 million and the resident population is 3.3767 million. As of 2018, Bengbu has jurisdiction over 4 municipal districts and 3 counties: Longzihu District, Bengshan District, Yuhui District, Huaishang District, Huaiyuan County, Wuhe County, Guzhen County, Bengbu High-tech Development Zone and Bengbu Economic Development Zone. Bengbu Municipal Government is located at 3115 Donghai Avenue, Bengshan District. According to the history, Bengbu is the place where pearls are collected in ancient times, so it is known as "Pearl City". On January 1, 1947, Bengbu was officially established as the first city in Anhui Province. In April 1952, Bengbu City was directly under Anhui Province. Bengbu