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.
Changtu County, the northernmost county in Liaoning Province, is the pilot unit of the county system of expanding power in Liaoning Province. it is a well-known agricultural county in the country, the largest peanut distribution center in Northeast China, the largest grain production base and livestock and poultry production and processing base in China. Changtu County has convenient transportation, there are Harbin-Dalian Railway, Pingqi Railway and Harbin-Dalian High-speed Railway. National Highway 102, National Highway 303 and Shen-Harbin Expressway pass through the territory. Changtu County has a strong industrial foundation. A modern industrial pattern based on the processing of building materials, chemical industry, machinery, textiles, agricultural and sideline products is taking shape. In September 2019, it was selected as a pilot county for the construction of medical community in a compact county.