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.
Wenchuan County, which belongs to Aba Tibetan Autonomous Prefecture of Sichuan Province, is located on the eastern edge of the Qinghai-Tibet Plateau, northwest Sichuan Province, Juchuan Northwest Plateau and the southeast of Aba Tibetan and Qiang Autonomous Prefecture. It is 84 kilometers from east to west and 105 kilometers from north to south, with a total area of 4084 square kilometers. The county seat is 1236 meters above sea level. It is 146 kilometers south from the provincial capital Chengdu and 202 kilometers north from the state capital Markang. It has jurisdiction over 9 towns and 3 townships. At the end of 2016, the registered population of Wenchuan County was 97615. Wenchuan is known as "the hometown of Dayu, the home of pandas and the hometown of Qiang embroidery". It is the birthplace of Dayu, the first ancestor of China, one of the four Qiang inhabited counties in China, and the ecological experience area of Qiang culture. Around the tourism brand of "World Wenchuan, Dayu hometown, Panda Home", with Dayu culture, Tibetan and Qiang culture, three Kingdoms culture,