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.
Yicheng District belongs to Luohe City, Henan Province. The central and southern part of Henan Province belongs to the plain area of the middle reaches of the Dasha River in the Huaihe River Basin. It is located at longitude 113o 45'10 east, longitude 114 °6'39, latitude 33 °34'37, latitude 33 °44'59, latitude 33 °34'39, respectively. It is bordered by Zhaoling District to the east, Zhaoling District and Yuanhui District to the southeast, Shahe River to the south, Wuyang County to the southwest, Linying County to the northwest and Linying County to the north, and Zhaoling District, Linying County, Zhoukou City and Xihua County to the northeast. The region has a total area of 413.1 square kilometers, with a total population of 528000 in 2012, and has jurisdiction over 8 townships and Shabei streets. Politics, Finance and economy of Luohe City