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.
Geji County belongs to the Ali area of Tibet Autonomous region of China. It is located in western Tibet, the source of the Shiquan River. The area is 47225 square kilometers (2010), of which the grassland area is more than 40, 000 square kilometers (2010) and the cultivated land area is more than 300 mu (2010). The total population is 15438 (2010). Geji is basically a pure animal husbandry county. The county is located in the Great Lake Basin of the Qiangtang Plateau, with an average elevation of more than 4800 meters, which is called "the roof of the world". Naboo is the political and cultural center of the county. In the first half of 2004, people generated 5.344 million yuan of income, an increase of 2.5 times over the same period in 2003. It has jurisdiction over 4 districts, 15 townships and 52 village committees.