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.
Pingshan County is a county under the jurisdiction of Yibin City. Because there is Baoping Mountain in the east of the county, the mountain is like a barrier, which gets its name. Pingshan County is located in the lower reaches of Minjiang River, Yibin City in the east, Leibo County and Mabian Yi Autonomous County in the west, Muchuan County in the north and Suijiang County in Yunnan Province in the south. The county seat is 42 kilometers away from Yibin and 300 kilometers away from Chengdu. By the end of 2018, Pingshan County had jurisdiction over 9 towns and 6 townships (including 2 Yi townships), with a total area of 1504 square kilometers, with a registered population of 312780 and 23 ethnic minorities. In 2017, the gross domestic product (GDP) of Pingshan County reached 4.80615 billion yuan, an increase of 8.5%. Among them, the added value of the primary industry is 1.62516 billion yuan, the secondary industry is 1.59822 billion yuan, and the tertiary industry is 1.58277 billion yuan.