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.
Weixin County, which belongs to Zhaotong City, Yunnan Province, is located in the joint of Yunnan, Guizhou and Sichuan provinces. It is commonly known as the "three provinces of chicken singing". During the long March, the Chinese Workers' and Peasants' Red Army held a famous "Taxi meeting" here. The county covers an area of nearly 1400 square kilometers, with more than 420,000 people of Han, Yi and other ethnic groups (2010). Weixin is a typical mountain county, whose agriculture is mainly corn, rice and flue-cured tobacco. Weixin County has Guandoushan stone carving group, Taxi conference site and large-scale Tiantai Mountain karst cave, Fan people hanging coffin and Tianxing National Forest Park. On April 30, 2019, the people's Government of Yunnan Province decided that Weixin County would withdraw from the sequence of poor counties.