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.
Shuangfeng County, which belongs to Loudi City, Hunan Province, was founded in 1951, named after the relative towering of two peaks in the county. Shuangfeng County is bordered by Xiangtan County and Hengshan County to the east, Hengyang County to the south, Shaodong County and Lianyuan City to the west, Loudi City and Xiangxiang City to the north. It is 61 kilometers wide from east to west and 59.2 kilometers from north to south. It covers an area of 1715.14 square kilometers, accounting for 0.81% of the total area of the province. The total population is 958000 (2015). Shuangfeng County has jurisdiction over 13 towns and 3 townships. The county government is based in Yongfeng town. Shuangfeng County is a mid-subtropical monsoon climate, the terrain is high in the west and low in the east, with hills and plains alternating. In 2015, Shuangfeng County achieved a GDP of 19.946 billion yuan. Places of interest include Huangchao Mountain, Xianshanzhai, Yongfeng Bridge, Zeng Guofan's former residence, Cai Hesen Memorial Hall and so on. Bimodal history