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.
Shawan County, the eastern gate of Tacheng area, is located in the middle of the northern foot of Tianshan Mountains in Xinjiang and the southern edge of Junggar Basin, under the jurisdiction of Tacheng area, with Shihezi City in the east, Hejing County in the south, Kuitun City and Dushanzi District in the west, and Karamay City in the north. Shawan County covers an area of 13100 square kilometers, with a total population of 216435 (2012). It is composed of 30 ethnic groups, including Han, Kazak, Hui and Uygur, and has jurisdiction over 9 towns, 3 townships, 5 agricultural and animal husbandry and forestry farms, 2 management offices and 250 village teams. Shawan County has successively won the titles of more than 20 state-level advanced counties, including scientific and technological progress, culture and sports, civil affairs, and more than 30 autonomous district-level advanced counties, such as the construction of grass-roots organizations, investment attraction, employment and re-employment, and has won eight consecutive autonomous region civilized counties and two Chinese civilized counties. two hundred and one