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.
Shangyu District, Shaoxing City, Zhejiang Province. Located in the east of Zhejiang Province, northeast of Shaoxing City, the south bank of Qiantang River. It is bordered by Yuyao City, Ningbo City to the east, Shengzhou City to the south, Keqiao District and Yuecheng District to the west, and Qiantang River to the north, facing Haining City and Haiyan County. The land area of the whole region is 1401.68 square kilometers, the topography is high in the south and low in the north, and the area of the low mountains and hills in the south and the water network plain in the north are half and half, showing a pattern of "five mountains, one water and four fields". After the adjustment of administrative divisions in November 2019, the region has jurisdiction over 8 streets, 10 towns and 3 townships. At the end of 2018, the resident population was 797100 and the registered population was 780400. According to the preliminary calculation, Shangyu District achieved a GDP of 91.652 billion yuan in 2018, an increase of 7.4% at comparable prices.