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.
Deyang, also known as Jingcheng, is a prefecture-level city in Sichuan Province. Located in the northeast of Chengdu Plain; located in the transition zone from Longmen Mountains to Sichuan Basin; the northwest has a mountain vertical climate and the southeast has a humid monsoon climate in the middle subtropics. The city has a total area of 5910 square kilometers, under the jurisdiction of 2 districts, 1 county, escrow 3 county-level cities; the registered population is 3.877 million in 2018. Adjacent to Chengdu, the provincial capital, Deyang is located at the intersection and overlap of the Silk Road Economic Belt and the Yangtze River Economic Belt, making every effort to create a new city in the north of Chengdu's international metropolis. Deyang has well-developed transportation, 50 kilometers away from Shuangliu International Airport and 24 kilometers away from Qingbai River, the largest railway container center in Asia. Deyang is a major technology and equipment manufacturing base in China because of the "third-line construction" national layout of modern large industry. 2017 1