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.
Pingxiang City, a county-level city in Guangxi Zhuang Autonomous region, is hosted by Chongzuo City, located in southern China, bordering Lang Shan in Vietnam, known as "the south gate of the motherland", and is the international city closest to ASEAN countries in China. It has four towns under its jurisdiction, with a land area of 650 square kilometers and a population of more than 100,000. Pingxiang City is 160 kilometers away from Nanning, the capital of Guangxi, and Hanoi, the capital of Vietnam (expressway), and borders with Vietnam's Liangshan Province on both sides of the southwest. The border line is 97 kilometers long. In the border area, there are two national first-class ports (highway) and Pingxiang port (railway), one second-class port and five border cities. It is the border port city with the largest number, the most variety and the largest scale of Guangxi ports. It is the largest and most convenient land passage from China to Vietnam and Southeast Asia. 1992 6