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.
Ankang City (AnKang) is located in the southeast of Shaanxi Province, with Qinling Mountains in the north, Bashan Mountain in the south and Han River running from east to west. The river valley basin (Ankang Basin) is in the middle, with an area between 31 °42 latitude and 33 °49 'north latitude and 108 °01 longitude and 110 °01' east longitude. It has jurisdiction over 1 district and 9 counties. Ankang is located in the hinterland of Qinba and the bank of Han River. It is known as & quot; Xi'an back Garden & quot;. Ankang City covers an area of 23391 square kilometers, with 289000 hectares of arable land. In 2016, Ankang has a resident population of 2.656 million. This area is a typical representative area of animals and plants in northern subtropical China, with rare animals such as antelope, crested ibis, giant panda, clouded leopard, giant salamander and so on. It is the main producing area of tea, silkworm cocoon, paulownia and raw lacquer in Shaanxi Province and Northwest China. Because within the territory