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.
Horgos, which belongs to Yili Kazakh Autonomous Prefecture of Xinjiang Uygur Autonomous region, is located in the western border of China, bordering Kazakhstan, five countries of Central Asia in the west and inland provinces and cities in the east. It is the end of National Highway 312 and Lianhuo Expressway. It is 90km away from Yining, the capital of Yili Prefecture, 670km from Urumqi, the capital of Xinjiang Uygur Autonomous region, 378km away from the central city of Central Asia and Almaty, the former capital of Kazakhstan. The area within the radius of 1000 km is the densely populated area, economically developed area and market center of Central Asia. As of 2016, Horgos has jurisdiction over four subdistrict offices, one ethnic township, one pasture and two bingtuan farms. At the end of 2015, the total population of permanent residents in the city (including bingtuan) was 87200. The area is 1908.