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.
Naidong District (Tibetan: Tibetan dialect, Tibetan Pinyin: Ningdong Zong) belongs to Shannan City, Tibet Autonomous region, located in the south-central part of the Tibet Autonomous region, the south of the Gangdise Mountains, the middle reaches of the Yarlung Zangbo River, and is the seat of the people's Government of Shannan City. It means "before the tip of the elephant trunk mountain" in Tibetan. The geographical coordinates of Nidong District are located between 28 °44 °N and 29 °36 °N, 91 °32 °N and 92 °02'E, bordering Zhabang County in the west, Mozhu Gongka County in Lhasa City in the north, surrounded by Qiongjie, Longzi and Cuomei counties in the south, and Sangri and Qusong counties in the east, with a total area of 2208.85 square kilometers, with a total area of 94.4km from north to south and 31.2km from east to west in the middle, with a total population of 76976 (