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.
Wanning City, which belongs to Hainan Province, is located on the southeast coast of Hainan Island, longitude 110.39 °E, latitude 18.8 °N, South China Sea to the east, Qiongzhong to the west, Lingshui to the south and Qionghai to the north. Wanning City has a total urban area of 4443.6 square kilometers, including a land area of 1883.5 square kilometers and a sea area of 2550.1 square kilometers. At the end of 2017, Wanning had a resident population of 573600. In 2017, Wanning achieved a regional gross domestic product (GDP) of 20.39 billion yuan. In November 2013, Wanning City won the title of "hometown of world longevity". In March 2019, it was selected into the list of the first batch of revolutionary cultural relics protection and utilization districts and counties. ...