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.
Chengcheng County, which belongs to Weinan City, Shaanxi Province, is located in the eastern part of Guanzhong Basin, Shaanxi Province. It is between 109o 46km east longitude-110o 05km east latitude and 34o 550045 "- 35o 2705km north latitude, with a total area of 1121 square km. Chengcheng County has a long history. It was built from the Northern Wei Dynasty, and the county name has been in use for 1540 years. The terrain is high in the north and low in the south, and the county is divided into "three beams and one original" by four rivers. It is a warm temperate semi-humid monsoon zone with an average annual temperature of 12 ℃, precipitation of 680mm, frost-free period of 204days and a large temperature difference between day and night. As of 2018, Chengcheng County has jurisdiction over 1 street and 9 towns. By the end of 2017, Chengcheng County had a resident population of 393224, with a gross domestic product (GDP) of 8.569 billion yuan.