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.
Zhiduo County is a county under the jurisdiction of Yushu Tibetan Autonomous Prefecture in Qinghai Province, which is located in the southwest of the province, the central and western part of the state border, and bordered by Xinjiang and Tibet Autonomous region in the west. The county government is stationed in Jiaji Borough (in Duocai Township). The county is bordered by Yushu County in the east, Hercynian escrow District in the west, Qumalai County and Haixi County in the north, and Zaduo County in the south. 921 kilometers away from the provincial capital Xining, 195 miles from the state capital, 109 National Highway and Qinghai-Tibet Railway pass through the waist. By the end of 2007, the total population of the county had reached 28200, mainly Tibetans, accounting for 97.8% of the total population, as well as Han, Hui, Qala and other ethnic groups. The total land area is 80200 square kilometers and it has jurisdiction over 6 townships. In 2007, the county's GDP reached 208.587 million yuan. On December 29th, 2018, Zhiduo County was killed.