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.
During the four dynasties of Jin, Yuan, Ming and Qing dynasties, it was changed to Jiaxian in the Republic of China and Jiaxian in September 1964. It is located on the west bank of the middle reaches of the Yellow River in northeastern Shaanxi Province, southeast of Yulin City, and on the southeast edge of Maowusu Sandy Land. It is bordered by Mizhi County in the west, Wubao County in the south, Shenmu County in the north, Suide County in the southwest and Yuyang District in the northwest. It has jurisdiction over 12 towns and one street, with a county area of 2144 square kilometers, 43000 hectares of arable land, and a registered population of 269700 (2017). Mung beans are exported to Japan and other countries. There are Jiayu, Jiami and Jiawu three trunk highways connected with the county branch roads and the newly built Taijia and Yujia expressways. There are Baiyun Mountain Temple, Xianglu Temple, Yunyan Temple and other famous landscapes. September 25, 2018, access to business