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.
Qinnan District, which belongs to Qinzhou City, Guangxi, is located in the center of the Beibu Gulf Economic Zone of Guangxi Zhuang Autonomous region, 100 kilometers north of the capital Nanning, bordering the Beibu Gulf in the north, Beihai City in the east, Fangchenggang City in the west and Qinzhou Port in the south. It is an urban central area of Beibu Gulf (Guangxi) Economic Zone, which integrates many functions and advantages, such as coastal industrial park, coastal cultural tourism resort, Guangxi coastal transportation hub, southwest of China and many other functions and advantages. By the end of 2013, Qinnan District, with a total area of 2255 square kilometers and a population of 560000, had jurisdiction over 12 towns, one overseas Chinese farm and four streets. In 2013, the GDP of Qinnan District reached 16.94 billion yuan, an increase of 14% over the same period last year, ranking first in terms of total volume and growth. Revenue was 540 million yuan, an increase of 16.5% over the same period last year.