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.
Ali is the only area in the Tibet Autonomous region, known as "Yangtong" around AD, "Nari" in the Yuan Dynasty and "Russia" in the Ming Dynasty. It is located in the southwest border of China, the west of Tibet Autonomous region and the north of Qinghai-Tibet Plateau (Qiangtang Plateau). It is bounded by Hetian area of Xinjiang Uygur Autonomous region and Bayingoleng Mongolia Autonomous Prefecture to the north, Naqu to the east, Xigaze to the southeast, Nepal, India and Kashmir to the southwest and west. According to the second land survey, the total area of the region is 337174.95 square kilometers, making it the second largest prefecture-level unit in Tibet after Naqu City. At the end of 2017, the region had jurisdiction over 7 counties, 7 towns and 30 townships, 11 neighborhood committees and 134 village committees. No. 6 Cultural Road, Shiquanhe Town, Gar County, Administrative Office. Resident population 10.74