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.
Gejiu City is a municipality under the jurisdiction of Honghe Hani and Yi Autonomous Prefecture, Yunnan Province, China, which is located between 102 °54'E and 103 °25'E and 23 °01'N 23 °36'. "Gejiu" is evolved from the transliteration of "fruit work" in the Yi language, which means a place to grow buckwheat and eat buckwheat. Gejiu is 280 kilometers away from the provincial capital Kunming and 200 kilometers from Vietnam. The city has a land area of 1587 square kilometers, with a total population of 453300, of which the urban population is 309500, the level of urbanization is 68.30%, the urban built-up area is 12 square kilometers, and the urban resident population is 180000. There are more than 120000 ethnic minorities living in Yi, Zhuang, Hui, Miao, Dai and Hani. Gejiu is a kind of metallurgy which mainly produces tin and produces lead, zinc, copper and other non-ferrous metals.