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.
Jiayu County, the ancient name of Shayangbao, gets its name from the meaning of "Jiayu in the south of the Book of songs". It is a county under the jurisdiction of Xianning City, Hubei Province, located in longitude 113 °39mm east and latitude 29 °48mm. It is located on the south bank of the middle reaches of the Yangtze River, bordering Wuhan to the north, Chibi to the south, Xianning to the east and Honghu to the west, and is an important part of Wuhan city circle. Jiayu County has a narrow terrain, 85 kilometers long and 5.7 kilometers wide, with a total area of 1017 square kilometers in 2016, including a land area of 712 square kilometers and a water area of 305 square kilometers. It has jurisdiction over 8 towns with a total population of 366577 (2018). Jiayu County is the first batch of areas open to the outside world and the Yangtze River economic belt.