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.
Anduo County, which belongs to Naqu City, Tibet, is located in northern Tibet, on the north and south sides of the famous Tanggula Mountains, adjacent to Zhiduo County, Zaduo County and Nierong County in Qinghai Province in the east, Xeni District in the south, Bango County and Shuanghu County in the west, and Golmud City in Qinghai Province to the north. It is the north gate of Tibet. Anduo County covers an area of about 100000 square kilometers and has jurisdiction over 4 towns, 9 townships, 79 administrative villages, and the county people's government in Pana Town. Anduo County is rich in natural mineral resources and is a natural wildlife kingdom. Special circumstances: Anduo County currently has several (immigration management) townships in the west of Qinghai Province. Anduo County was hit by a severe snowstorm in the winter of 1962. The following year, it was called Township through some places in Tanggula Town of Qinghai Province, Zhiduo County, Zaduo County and Golmud City. Later, several immigration management systems were set up.