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.
Urumqi, referred to as Urumqi, formerly known as Dihua, is the capital of Xinjiang Uygur Autonomous region, the political, economic, cultural, scientific, educational and transportation center of Xinjiang, and the largest city farthest from the sea in the world. Approved by the State Council, it is an important central city in northwest China and an international trade center facing Central Asia and West Asia. By 2018, the city had jurisdiction over seven districts and one county, with a total area of 14216.3 square kilometers, a built-up area of 436 square kilometers, a resident population of 3.5058 million, an urban population of 2.6157 million, and a urbanization rate of 74.61 percent. Urumqi is located in northwest China, central Xinjiang, the center of the Eurasian continent, the northern foot of the middle part of the Tianshan Mountains, the southern margin of the Junggar Basin, adjacent to the countries of Central Asia, known as the "capital of the heart of Asia", is the second Eurasian University.