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.
Xiangyun County is one of the counties under the jurisdiction of Dali Bai Autonomous Prefecture in Yunnan Province. it is located in the west-central part of Yunnan Province, bordering Dayao, Yao'an and Nanhua counties in the east, Midu County in the south, Dali City in the west and Binchuan County in the north. Xiangyun is one of the counties with earlier development and better economic development in Yunnan. it has been the political, economic and cultural center of northwest Yunnan for a long time. The name of Yunnan Province comes from Yunan County, which is located in Xiangyun in history, so Xiangyun is known as "the hometown of colorful clouds" and "the source of Yunnan". Xiangyun County is the throat of traffic in western Yunnan, the necessary place leading to the eight prefectures in western Yunnan, and the eastern gate of Dali Prefecture, only 282 kilometers away from Kunming and 48 kilometers to Dali Airport. Xiangyun County covers an area of 2425 square kilometers and has jurisdiction over 8 towns, 1 township and 1 nationality township. The population of Xiangyun County at the end of 2012 is