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.
Aksu region, one of the five regions of Xinjiang Uygur Autonomous region, is based in Aksu City. It is located in the middle of Xinjiang Uygur Autonomous region, the southern foot of the middle part of Tianshan Mountains, the north of Tarim Basin, Bayingol Mongolia Autonomous Prefecture in the east, Kizilsu Kirgiz Autonomous Prefecture in the west, Kashgar Autonomous region in the southwest, Hotan Autonomous Prefecture in the south, Yili Autonomous Prefecture in the north and Kyrgyzstan and Kazakhstan in the northwest. The total area is 132500 square kilometers, accounting for 8% of the area of Xinjiang. Aksu area has jurisdiction over 1 city and 8 counties, with a total of 84 townships. In 2016, Aksu has a total population of 2.5083 million (excluding the city of Alar), which is composed of 36 ethnic groups and is a multi-ethnic area dominated by Uygur. Aksu region has won the country successively.