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.
Guyuan, a prefecture-level city under the jurisdiction of Ningxia Hui Autonomous region, known as Dayuan, Gaoping, Xiaoguan and Yuanzhou in ancient times, is located in the south of Ningxia Hui Autonomous region, is a deputy central city of Ningxia Hui Autonomous region, and is located on the northwest edge of China's Loess Plateau. It is a typical continental climate; it has jurisdiction over 1 district and 4 counties, with a total area of 10540 square kilometers; by the end of 2018, the total number of permanent households in Guyuan is 352000, the total resident population is 1.2424 million, and the total registered population is 1.5077 million. Guyuan is located in the center of the triangle composed of the three provincial capitals of Xi'an, Lanzhou and Yinchuan, one of the five prefecture-level cities of Ningxia and the only non-Yellow River city. Shaanxi-Gansu-Ningxia Revolutionary Base Revitalization Planning Central City, South Ningxia Regional Central City, political, Economic, Cultural Center and Transportation Hub