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.
Phoenix, which belongs to Xiangxi Tujia and Miao Autonomous Prefecture of Hunan Province, is located on the western edge of Hunan Province, the southwest corner of Xiangxi Tujia and Miao Autonomous Prefecture, bordered by Luxi County to the east, Jishou City and Huayuan County to the north, Mayang Miao Autonomous County in Huaihua to the south, and Songtao Miao Autonomous County in Tongren Prefecture of Guizhou Province to the west. It is between 109 °18 miles east longitude 109 °48 kilometers east longitude and 27 °44 kilometers north latitude, 28 degrees 19 degrees north latitude, 66 kilometers from north to south and 50 kilometers from east to west, with a total area of 1759.1 square kilometers. It is about 0.84% of the area of Hunan Province, accounting for 8.12% of the whole prefecture area. Phoenix is a famous historical and cultural city in China, one of the first strong tourist counties in China, a national AAAA scenic spot, and one of the eight counties and cities under the jurisdiction of Xiangxi Tujia and Miao Autonomous Prefecture in Hunan Province.