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.
Xunyang County is located in the southeast of Shaanxi Province, in the eastern part of Qinba Mountains, between longitude 103 °58'to 109 °48 'east and latitude 32 °29' to 33 °13 'north. It is bordered by Baihe County and Yunxi County in Hubei Province to the east, Pingli County to the south, Zhushan County and Zhuxi County in Hubei Province to the south, Hanbin District to the west, and Zhenan County and Yunxi County in Hubei Province to the north. The county is about 82 kilometers from north to south, 79 kilometers from east to west and 390 kilometers from east to west. The county seat is located at the confluence of the Han River and Xunhe River. the new urban area extends upward for several kilometers along the west bank of the Xunhe River. The northern section is the old city of the county seat, and the place where the Xunhe River enters the Han River is in the shape of "S", so it is also called "Taiji City". The Xiang-Yu Railway has set up a station in the Liuwan community in the northwest of the county, which runs 1518 kilometers from Xiangyang, Zhengzhou and Shijiazhuang to the west of Beijing and west to Chengdu via Ankang and Dazhou.