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.
Xiji County, which belongs to Guyuan City, Ningxia Hui Autonomous region, is located at the western foot of Liupan Mountain in the south of Ningxia. Between east longitude 105 °20 & #39;-106 °04 & #39;, north latitude 35 °35 & #39;-36 °14 & #39;. It is 67 kilometers from east to west, 74 kilometers from north to south, 63 kilometers from Guyuan to the east and 391kilometers from Yinchuan, Ningxia, with a total area of 3130 square kilometers. As of 2018, it has jurisdiction over 4 towns and 15 townships with a total population of 496000. The county government is resident in Jiqiang Town. Xiji County, established on October 10, 1942, is the most populous county in Ningxia, inhabited by ethnic minorities, and a key county for poverty alleviation and development in the country and autonomous region. Xiji County is still Hong.