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.
Zhangjiagang City, belonging to Suzhou City, Jiangsu Province, is located in the east of Chinese mainland, on the south bank of the lower reaches of the Yangtze River, connected with Changshu in the southeast, Suzhou and Wuxi in the south, Jiangyin in the west, and the Yangtze River in the north, across the river from Rugao and Jingjiang River. the total area is 986.73 square kilometers, of which the land area is 777 square kilometers and the water area is 195.67 square kilometers. Zhangjiagang City, formerly known as Shazhou, was abolished in September 1986, and Zhangjiagang City was established after Zhangjiagang, a natural good port in the territory. By 2018, there were 8 towns under the jurisdiction of Zhangjiagang City, and there were 7 functional areas with a resident population of 1.2606 million, achieving a GDP of 272.018 billion yuan, of which the added value of the primary industry was 3.063 billion yuan and that of the secondary industry was 1423.6.