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.
Baiyin, prefecture-level city of Gansu Province. Located in the middle of Gansu Province, located in the transitional zone between the Loess Plateau and Tengger Desert, most of the territory is mountainous, mountainous and wide valley plain coexist; it is the transition zone from mid-temperate semi-arid zone to arid zone. The city has a total area of 21158.7 square kilometers and has jurisdiction over 2 districts and 3 counties. By the end of 2018, Baiyin had a resident population of 1.7342 million, an increase of 4900 over the end of last year. Baiyin City is located in the upper reaches of the Yellow River and the middle of Gansu Province, located in the confluence zone of the ancient Silk Road and the Yellow River, connecting the desert to the north, Qinghai and Tibet to the south, the Central Plains to the east and the western region to the west, 69 kilometers away from the provincial capital Lanzhou and 46 kilometers away from Zhongchuan Airport. It is a strategic channel connecting the subcontinental bridge, a transportation corridor and an energy logistics channel to countries along the Silk Road. The territory of Baiyin