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.
Zhongwei City, referred to as & quot; Wei & quot;, belongs to Ningxia Hui Autonomous region, is located in the central and western part of Ningxia Hui Autonomous region, Ningxia, Inner Mongolia and Gansu provinces. It is the first self-flow irrigation city in the middle and upper reaches of the Yellow River, with a total area of 17000 square kilometers. The topography of Zhongwei City is high in the southwest and low in the northeast, with an average elevation of 1225 meters in the urban area. the geomorphology is divided into five units of the Yellow River alluvial plain, platform, desert, mountains and hills, which belongs to a typical temperate continental monsoon climate. Due to the influence of desert, the sunshine is sufficient and the temperature difference between day and night is large. Zhongwei Yellow River diversion Irrigation area of 1.11 million mu, is an important commercial grain, aquatic products and facility vegetable production base in Northwest China. As of 2016, Zhongwei City has jurisdiction over Shapotou District, Zhongning County and Haiyuan County. 2016