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.
Pucheng County (ancient Pucheng County, Jianning Prefecture) is a county under the jurisdiction of Nanping City, Fujian Province, the hometown of Dangui in China. Located at the northernmost tip of Fujian Province and the junction of Fujian, Zhejiang and Jiangxi provinces, it is the "north gate" of Fujian. It has been the first pass for the Central Plains to enter Fujian since ancient times, bordering Jiangshan City, Longquan City, Suichang County in Zhejiang Province and Guangfeng County in Jiangxi Province respectively. It is adjacent to Jianyang City, Wuyishan City and Songxi County in Fujian Province. The county has jurisdiction over 2 streets, 9 towns, 8 townships and 296 villages. At the end of 2006, the registered population was 407000, of which 71600 were non-agricultural. Except for Shibei Town, Shuibei Street Town and other villages and towns, the dialect of northern Fujian is spoken in most of the other areas. The county covers an area of 3383 square kilometers, which is the third largest county in Fujian Province, with a mountain area of 4.374 million mu and cultivated land area.