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.
Huadu District, Guangzhou Municipal District, is located in the south-central part of Guangdong Province, the north of the Pearl River Delta and the north of Guangzhou. With a total area of 970.04 square kilometers, the region is located in longitude 112o 57707 "~ 113o 28010km east and latitude 23 °14057" ~ 23 °37818 "north. It is connected with Conghua District in the east, Sanshui District and Nanhai District in Foshan City in the west, Baiyun District in the south and Qingcheng District in Qingyuan City in the north. Guangzhou has "North Gate", "back Garden", "Leather Capital of China" and other laudatory names. Beijing-Guangzhou Railway and Wuhan-Guangzhou passenger dedicated Line run through the whole territory. Beijing-Hong Kong-Macao Expressway, Guang-Qing Expressway, Airport Expressway, Guang Le Expressway, Zhaohua Expressway, Guangzhou second Ring Road, North second Ring Road and Jiebei Expressway constitute the north-south and east-west highway network in Huadu. Liuxi River in the east and Bajiang River in the west