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.
Jilong County is located in the southwest of Tibet Autonomous region and southwest of Xigaze City, with geographical coordinates ranging from 84 °35'E to 86 °20 °E and 28 °3'to 29 °3'N. It is bordered by the Kingdom of Nepal to the south and southwest, with a border of 162 km, bounded by the Brahmaputra River to the north and Sagar County to the north, and Nieramu County to the east. The county government is stationed in Zongga town. One river and two rivers (Yarlung Zangbo River, Donglin Zangbo River, Jilong Zangbo River) run through the whole territory, with about 300 square kilometers of Jilong basin. Jilong County has jurisdiction over 2 towns and 4 townships, with a total area of 9300 square kilometers. The total population is 10,000 (2003). In 2005, the county's GDP actually completed 101.16 million yuan. In 2017, Jilong County withdrew from poor counties (districts).