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.
Henan Mongolian Autonomous County is the only Mongolian Autonomous County in Qinghai Province, commonly known as "Henan Mengqi", which has the highest proportion of Mongolian population in China. It is located in the southeast of Qinghai Province, facing Xiahe County and Luqu County of Gannan Tibetan Autonomous Prefecture of Gansu Province to the east, Maqu County of Gannan Tibetan Autonomous Prefecture of Gansu Province to the south, Maqin County of Guoluo Tibetan Autonomous Prefecture of Qinghai Province and Tongde County of Hainan Prefecture in the southwest, adjacent to Zeku County in the north, located in the joint of three provinces of Qinghai and Gansu, known as the south gate of Qinghai Province. The county covers a total area of 6997.45 square kilometers and is 3600 meters above sea level. It has jurisdiction over one town, four townships, two communities, 39 animal husbandry committees, 135 animal husbandry cooperatives and four Tibetan Buddhist monasteries. As of 2011, the total population was 40, 000, of which 93.21% were Mongolians. Henan County is the largest organic animal husbandry student in China.