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.
Hongsibao District, Wuzhong City, Ningxia, formerly known as Hongsibao Development Zone, is the second municipal district of Wuzhong City, Ningxia Hui Autonomous region. It is the main battlefield of the National large Water Control Project-Ningxia Poverty Alleviation and Yellow River Irrigation Project ("1236" Project). It is the largest ecological poverty alleviation and immigration concentration area in China. Hongsibao District of Wuzhong City was established with the approval of the State Council in September 2009. the administrative area covers an area of 2767 square kilometers. as of 2013, it has jurisdiction over 2 towns, 3 townships, 1 street, 61 administrative villages and 2 urban communities, with a total population of 179390. Among them, the Hui population accounts for 61% of the total population. Hongsibao District is located between Yanbing Mountain, Daluo Mountain and Niushou Mountain, facing Yanchi to the east, Zhongning to the west, concentric to the south, Litong District and Lingwu to the north, about 80 kilometers from east to west and 40 kilometers from north to south.