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.
Dongshan County (Zhangpu County, Zhangzhou Capital, Zhaoan County) belongs to Zhangzhou City, Fujian Province. Dongshan is located on the west bank of the Taiwan Strait and southern Fujian Province. Dongshan County is the sixth largest island county in China and the second largest island county in the province, with a total area of 248.9 square kilometers. Dongshan Island consists of the main island and 67 surrounding islands, shaped like a seven-star arch moon, shaped like a lifelike butterfly, so it is called Butterfly Island. As of 2013, the main island covers an area of 248.34 square kilometers and has national economic and technological development zones, tourism economic development zones, 7 towns, 61 administrative villages and 16 communities. 2017. In 2017, the total registered population of Dongshan County was 219081. In 2017, Dongshan County achieved a GDP of 20.287 billion yuan. Dongshan has won excellent tourist counties in China, the best tourist destination in Fujian Province, and Fujian Province.