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.
Lixian belongs to Baoding City, Hebei Province, the hinterland of Beijing, Tianjin and Stone Triangle, and the junction of Baoding, Cangzhou and Hengshui. Lixian has a total area of 650 square kilometers. In 2013, Lixian has a total population of 510000, including an agricultural population of 400000. Lixian has 13 townships (8 towns and 5 townships) and 232 administrative villages. Lixian County is located in the middle of the plain of the western structural belt of Jizhong Depression, Bohai Bay Basin. The topography and geomorphology are all plain formed by Quaternary alluvial and alluvial deposits. The general topography is high in the southwest and low in the northeast, with an average altitude of 15.6 meters. There is no obvious fluctuation. Lixian is a warm temperate semi-arid region in the eastern monsoon region, with significant continental monsoon climate, windy and dry spring, rainy and hot summer, crisp autumn, dry and cold winter, four distinct seasons, light and heat, and rich water resources. two