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.
Karamay City, one of the four prefecture-level cities in Xinjiang Uygur Autonomous region, is resident in Karamay District. It is an important national petroleum and petrochemical base and a new type of industrialized city built in Xinjiang. Karamay is located in the west of Junggar Basin, the central area of Eurasia and Pan-Central Asia, and is the gathering area of the world's petroleum and petrochemical industry. Karamay, the Uyghur language means "black oil". Karamay is a city named after oil, named after a group of natural asphalt hills in the northeast corner of the city. Karamay is the first large oil field to be explored and developed since the founding of New China. It was founded in 1958. In 2002, its crude oil output exceeded 10 million tons, making it the first large oil field in western China with a crude oil output of more than 10 million tons. Kramer, December 20, 2011