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.
Yangdong District belongs to Yangjiang City, Guangdong Province, bordering Yangchun City, Jiangcheng District and Enping City in the east, west and north respectively, and the South China Sea to the south. The coastline is more than 130km long and the land area is 1830 square kilometers. It is between 111 °42 degrees east longitude 112 °21 degrees east longitude and 22 degrees 15 'north latitude. In 2013, Yangdong District has jurisdiction over 11 towns (including 6 agricultural and forestry farms), a total of 171villages, 1688 village (resident) groups and 1488 natural villages. At the end of 2014, there were 498800 permanent residents and 502700 registered residents. In 2014, the region's gross domestic product (GDP) reached 25.808 billion yuan, an increase of 11.5% over the same period in 2013. Yangdong District is a national project pilot county with strong intellectual property rights.