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.
Xining, known as Qingtang City, Xiping County and Shanzhou in ancient times, is the capital of Qinghai Province, the political, economic, scientific and educational, cultural, transportation and communication center of Qinghai Province, and an important central city in the northwest region approved by the State Council. By 2019, the city had jurisdiction over five districts and two counties, with a total area of 7660 square kilometers, a built-up area of 129 square kilometers, a resident population of 2.3711 million, an urban population of 1.7098 million, and a urbanization rate of 72.1 percent. Xining is located in the eastern part of Qinghai Province, swimming in the river valley basin in the Huangshui River. It is the eastern gateway of the Qinghai-Tibet Plateau and the necessary place for the ancient "Silk Road" South Road and "Tangbo Ancient Road". It has been the northwest traffic road and military important place since ancient times. Known as the "key to the West Sea" and the throat of the sea, it is one of the high-altitude cities in the world and is also the State Council.