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.
Menyuan Hui Autonomous County is located in the northeast of Qinghai Province, under the jurisdiction of Haibei Tibetan Autonomous Prefecture, in the east of Haibei Tibetan Autonomous Prefecture and adjacent to Gansu Province in the east and north. It is 150 kilometers away from the provincial capital Xining and 250 kilometers away from Haiyan County, the capital of Haibei Prefecture. The total area is 6896 square kilometers. Menyuan County was established in 1929, Menyuan Hui Autonomous region was established in 1953, and changed to Menyuan Hui Autonomous County in 1955. In 2013, the GDP of Menyuan Hui Autonomous County reached 292 million yuan. Hui is the main ethnic group, accounting for about 40% of the total population, as well as Han, Tibetan, Turkish, Mongolian, Salar and other ethnic groups. The total population is 155800 (2013). The original name of Menyuan County was "Xianyuan" (Xi, m é n). Because the writing of the word "Qing" was too complicated, it was unified and simplified.