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.
Milin County is located in the southeast of Tibet Autonomous region, southwest of Linzhi City, the middle and lower reaches of the Brahmaputra River, between the Nyainqentangula Mountains and the Himalayas, connected with Motuo County in the southeast, Lang County in the west, Linzhi County in the north, Gongbujiangda County in the northwest, and Longzi County in the south. The total area is 9471 square kilometers, the terrain is high in the west and low in the east, with an average elevation of 3700 meters. It belongs to the temperate semi-humid monsoon climate of the plateau, with an average annual temperature of 8.2 ℃, annual precipitation of 641mm and sufficient sunshine. Milin County, with a total population of 23000, has jurisdiction over 3 towns and 5 townships (one of the ethnic townships) and 100 villagers' committees. The county government is located in Dongduo Village, 480 kilometers away from Lhasa, the capital of the autonomous region, and 72 kilometers away from Bayi District, where the people's Government of Linzhi City is located.