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.
Eryuan County is one of the counties under the jurisdiction of Dali Prefecture, Yunnan Province. It is located in the north of Dali City, the source of Erhai Lake. With a land area of 2875 square kilometers, it is an ethnic minority county inhabited by 24 ethnic groups, including Han, Bai, Yi, Hui, Dai and Lisu, with a total population of 320400 at the end of 1999. Because of its rich natural resources, Eryuan is praised as "land of fish and rice", "hometown of plum", "hometown of dairy cows", "hometown of hot springs", "hometown of orchids", "hometown of plateau water" and "hometown of suona". On September 29, 2018, Eryuan County was approved to withdraw from the poverty-stricken county after being studied by the Yunnan provincial party committee and provincial government.