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.
Pingding County, which belongs to Yangquan City, Shanxi Province, is located in the east of the middle of Shanxi Province, the western foot of the middle part of Taihang Mountain and the southeast of Yangquan City. The geographical coordinates are 37 °39 °30 "- 38 °07" 30 "N and 113 °25" 55 "- 114 °02" 33 "E, respectively. It is bordered by Yu County and Yangquan City in the north, Shouyang County in the west, Xiyang County in the south, and Jingxing County in Hebei Province in the east. It is the main road of Shanxi-Hebei thoroughfare and the east gate of Shanxi Province. The county seat is 9 kilometers away from Yangquan city and 127 kilometers away from Taiyuan, the provincial capital. County east-west longest 54 km, north-south widest 50.4 km, covering an area of 1391 square kilometers, jurisdiction over 8 towns and 2 townships, population 345000. There are Niangziguan, Guanshan, Kaihe Temple, Guguan Great Wall and other famous scenic spots. In 2018, Pingding County completed the total regional production.