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.
Bayi District, which belongs to Linzhi City, Tibet Autonomous region, is located in the southeast of China's Tibet and at the southeast foot of the Nianqing Tanggula Mountains. Yarlung Zangbo meets the Niyang River here. It is the lowest elevation area of the Qinghai-Tibet Plateau and is known as "Jiangnan of Tibet". Bayi District covers an area of 10238 square kilometers, with a cultivated land area of 38000 mu, a grassland area of 565000 mu and a forest area of 5.02 million mu. The average elevation of Bayi District is 3000 meters above sea level, with a relative height difference of 2200-4700 meters. It is located at the peak of Garabaili at the junction of Bayi and Milin, with an elevation of 7294 meters. Plants grow from the subtropical zone to the cold zone, known as the "green treasure house". In 2014, the GDP of Bayi District (formerly Linzhi County) reached 4.555 billion yuan, and the financial revenue broke through the 100 million yuan mark for the first time, reaching 1.2 million yuan.