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.
Lanxi County is a county of Suihua City, Heilongjiang Province. The geographical coordinates are 126 °22 12 "to 126 °28" E and 46 °12 "57" to 46 °18 "2" N, belonging to the semi-humid monsoon climate in the cold temperate zone. Qinggang County and Wangkui County in the north, Beilin area in the east, Zhaodong City on the western boundary, and Anda City in the northwest, 67 kilometers away from the provincial capital Harbin. Lanxi County covers an area of 2499 square kilometers. As of 2010, Lanxi County has 2.16 million mu of arable land, 340000 mu of grassland and 106300 mu of water. The total population is 530000 (2013), of which the agricultural population is 388000 and the per capita cultivated land is 5.6mu. There are 15 rural towns, 105 administrative villages and 773 natural villages in the county. The main food crops in Lanxi County are