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.
Xiapu County (ancient Xiapu County, Funing Prefecture) is located in the northeast of Fujian Province. it is the oldest county in eastern Fujian, and it was once the political, economic and cultural center of eastern Fujian. Because it is located along the coast, it is a semi-island area, with a land area of 1489.6 square kilometers and a sea area of 29592.6 square kilometers. The coastline is 404km long, accounting for 1/8 of the province, ranking first in the province. There are 185 large and small islands. The long coastline and numerous islands and harbours have become the geographical features of Xiapu. It is a port city on the northeast wing of the economic zone on the west coast of the Taiwan Strait in southeastern China. It is a coastal economic open county approved by the State Council of the people's Republic of China, the earliest trade port opened to Taiwan in Fujian, "the hometown of Chinese kelp" and "the hometown of Chinese Laver". It is known as "Fujian and Zhejiang want to rush" and "land of fish and rice".