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.
Liannan Yao Autonomous County is located in the northwest of Guangdong Province, north of the Tropic of Cancer, between latitude 24 °17 °16 "- 24 °56 °2" north and longitude 112 °2 °2 "- 112 °29 °1" east. It is bordered by Lianzhou City in the northeast, Yangshan County in the southeast, Huaiji County in the south, Lianshan Zhuang and Yao Autonomous County in the west, and Jianghua Yao Autonomous County in Hunan Province in the northwest. There are 71 village neighborhood committees in 7 towns (Sanjiang, Zhaigang, Damashan, Xiangping, Daping, Wushui, three rows). The county seat is located in Sanjiang Town. After the opening of National Highway 107, the county seat is 236 kilometers away from Guangzhou Highway and 120 kilometers away from Pingshi Railway Station. The Yao people live in 80% of the county, and there are Yao villages everywhere on the high mountains and mountains.