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.
Zhenjiang, a prefecture-level city under the jurisdiction of Jiangsu Province, is an important port and scenic tourist city in the Yangtze River Delta, with a geomorphological trend of high in the west and low in the east, high in the south and low in the north, belonging to the north subtropical monsoon climate, with a total area of 3847 square kilometers. it has jurisdiction over 3 districts and 3 county-level cities; the resident population is 3.1964 million in 2018. Zhenjiang changed its name many times: it was called "Zhu Fang" in the Spring and Autumn period, "Guyang" in the warring States period, "Dantu" in the Qin Dynasty, "Jingkou" in the three Kingdoms, "South Xuzhou" in the Southern Dynasty and Song Dynasty, and "Runzhou" after the unification of the Sui Dynasty. The name of Zhenjiang has been changed since the Northern Song Dynasty. Zhenjiang is located in the southeast coast of China, southern Jiangsu, the center of the north wing of the Yangtze River Delta, the only confluence hub of the Yangtze River and the Beijing-Hangzhou Grand Canal; Changzhou and Wuxi to the south, Yangzhou to the north and Nanjing to the west; it is an important traffic center in East China. Within the territory