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.
Jiajiang County is the porcelain capital of western China, which belongs to Leshan City, Sichuan Province and is located in the southwest of Sichuan Province. The total area of Jiajiang County is 749 square kilometers. In 2006, Jiajiang County had jurisdiction over 22 townships with 348900 people. Jiajiang County is a strong industrial county in Leshan City. In 2016, the county's gross domestic product (GDP) reached 13.7 billion yuan, an increase of 9% over the previous year. Jiajiang County is the tourism pilot county of Leshan City. Dongfengyan in Jiajiang County is the first World Irrigation Engineering Heritage in Sichuan Province, and it is also the third World Heritage site in Leshan after Leshan Giant Buddha and Emei Mountain. Jiajiang County is known as the Pearl of Tianfu, and it is also the hometown of Chinese martial arts, Chinese Yangko and Chinese calligraphy and painting paper.