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.
Jiuzhi County is a county under the jurisdiction of Guoluo Tibetan Autonomous Prefecture in Qinghai Province and one of the animal husbandry production bases in Qinghai Province. It is located in the southeast of the state, at the junction of Qinghai, Sichuan and Gansu provinces, adjacent to Aba County in Sichuan Province in the southeast, Banma County in the south, Dari County in the west, the Yellow River and Gande County in the northwest, and Maqu County in Gansu Province in the northeast. Jiuzhi established the people's Government of Jiuzhi County in March 1955, which has jurisdiction over 5 townships and 1 town. The total area is 8757.25 square kilometers. As of 2012, the total population of Jiuzhi County is 26000, mainly Tibetan, Han, Hui, Mongolian, Tu and other ethnic groups, of which 24000 are Tibetans, accounting for 95.6% of the total population. There are more than 10 Tibetan Buddhist monasteries in Jiuzhi County. In 2013, the GDP of Jiuzhi County was 269 million yuan, an increase over the same period last year.