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.
Zixi County, which belongs to Fuzhou City, is located in the east-central part of Jiangxi Province and in the east of Fuzhou City, between 27 °28 degrees north latitude and 117 °17 'east longitude. Zixi County is not only the east gate of Jiangxi, but also an important passage from Jiangxi to Fujian. It is bordered by Guangze County, Fujian Province in the east, Lichuan County in the south, Nancheng County in the west, Jinxi County and Guixi City in the north, with a total area of 1251.03 square kilometers. The total population is 126000 (2012). It has jurisdiction over 2 townships, 5 towns, 5 state-owned forest farms and 70 administrative villages. Zixi is the hometown of Chinese bread, Zixi Bread more than 7000 bakeries throughout the country, but also located in Russia, Vietnam, Hong Kong and other places. Zixi is a national eco-tourism county, the national ecological demonstration area and so on. Ecological Index of Zixi in 2009