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.
Yining City (Uygur: Latin Uygur: Ghulja) is located in the northwest border of Xinjiang, in the middle of the Yili River Valley Basin. The geographical coordinates are between latitude 43 °50 "44 °09 'north and longitude 80 °04" 81 °29' east. Yining County to the east, Huocheng County to the west, Yili River to the south and Chabuchal Xibe Autonomous County across the river, and Kogurqin Mountain to the north. It is 509 km from Urumqi by air, 614 km by railway and 702 km by road. Northeast to Tacheng highway mileage of 830 km, to Altay city highway mileage of 989 km. The city center is 639 meters above sea level. The total area of the city is 761.34 square kilometers, with a length of 52.08km from north to south and 35.5km from east to west. Two towns, seven townships under the jurisdiction of Yining