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.
Hualong District is the municipal district of Puyang City, which is located in the northeast of Henan Province and at the junction of Hebei, Shandong and Henan provinces. it was established in 1986, with a total area of 119square kilometers and cultivated land of 7360 hectares. In 2008, the total population was 349700, of which the agricultural population was 73000. In 2012, the GDP of Hualong District reached 7.083 billion yuan, the total retail sales of consumer goods reached 5.419 billion yuan, and the total investment in fixed assets of the whole society reached 9.84 billion yuan. Hualong District, the only administrative district under the jurisdiction of Puyang City, is the political, economic and cultural center of Puyang City and the headquarters of Zhongyuan Oilfield. Hualong District has been named as "National Advanced Zone for Scientific and technological Progress", "National Experimental Zone for Sustainable Development", "National Community Health Service demonstration area" and "National Social Security Ensemble".