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.
Pishan County, Guang Xu 28 years home county, named after the ancient country. Uighurs call Pishan County "Guma", its meaning is still uncertain, there are "hut", "cage", "suspicious place" and so on. Interpretation of Tongwen Chronicles of the Western regions: "it is suspicious." In the early days, after their people practiced Islam, some of them fled because of their names. " Pishan County is located in the southern part of Xinjiang Uygur Autonomous region, the southern edge of the Taklimakan Desert and the northern foot of the Karakoram Mountains. It is bordered by Hotan County and Moyu County in the east, Yecheng County in the west, India and Pakistan in Kashmir in the south, and Maigaiti County and Bachu County in the north. It is located in longitude 77 °31'to 79 °38 'east and latitude 35 °22' to 39 °01 'north. The county is 423 kilometers from north to south and 67.5 to 144 from east to west.