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.
Dulan County is located in the southeast of Haixi Mongolian-Tibetan Autonomous Prefecture of Qinghai Province. Dulan (which means "warm" in Mongolian) has a total area of 45270 square kilometers. As of 2013, the total population was nearly 100000. Mainly Han nationality, as well as Tibetan, Mongolian, Hui, Turkish and other ethnic minorities. The county people's government is stationed in Cn Wusu Town, 205 kilometers away from Delingha, the state capital, and 428 kilometers from Xining, the provincial capital. Dulan County is located in the southeast corner of Qaidam Basin. The whole territory can be divided into two geomorphological types: Khan Buda Mountain area and Qaidam Basin Plain. Gobi, desert, valley, rivers and lakes, hills, plateaus, mountains and other topography are distributed in turn. There are more than 40 rivers, such as Shaliu River, Tuoso River, Cn Wusu River and so on. It belongs to the arid continental climate of the plateau, with an average annual temperature of 2.7 ℃ and a minimum extreme temperature of-29.8.