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.
Hejiang County, which belongs to Luzhou City, Sichuan Province, is located at the junction of Sichuan, Chongqing and Guizhou, on the southern edge of Sichuan Basin. It is adjacent to Jiangyang District, Naxi District and Lu County in the west, Jiangjin District of Chongqing City in the east, Yongchuan District in the north and Chishui City and Xishui County in Guizhou Province to the south. Hejiang County is 38.7km away from Luzhou, 260.1 km from Chengdu and 109.2 km from Chongqing. It is the first port county of the Yangtze River out of Sichuan. There are 54 km of the Yangtze River and 57 km of golden waterway of Chishui River. Hejiang County, which was founded in the second year of Yuanding in the Western Han Dynasty (115 BC), is one of the three earliest counties in the upper reaches of the Yangtze River. There are national forest parks, provincial scenic spots, Fubao tourist area, Chinese historical and cultural towns Fubao Ancient Town and Yaoba.