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.
Chayu (cha yu) County, one of the three corners of southern Tibet (also Menyu and Luoyu), belongs to Linzhi City, Tibet, located in the southeast of Tibet Autonomous region, Deqin County, Diqing Tibetan Autonomous Prefecture, Yunnan Province, and Zuogong County, Changdu Prefecture, Yunnan Province to the east, Motuo County (Luoyu) to the west, Changdu to the north, Myanmar and India to the south. It covers an area of 31659 square kilometers (19200 square kilometers in 2003, and the rest is controlled by India). Chayu County has jurisdiction over 3 townships and 3 towns with a total population of 25823 (2003). In 2005, Chayu County achieved a GDP of 176.25 million yuan. In 2016, the county's GDP was 773 million yuan, financial revenue was 35 million yuan, retail sales of consumer goods were 137 million yuan, and the per capita net income of farmers and herdsmen was 9276 yuan. Inspection