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.
Siping, a prefecture-level city in Jilin Province, is located in the central hinterland of Songliao Plain and at the junction of Liao, Jilin and Mongolia provinces. Siping is an important transportation hub and logistics node city in Northeast China, which leads to the Yangtze River Delta and Beijing-Tianjin-Hebei in the eastern part of Jilin, Heilongjiang and Inner Mongolia. Siping has an area of 14323 square kilometers and a population of 3.204 million, including an urban area of 1100 square kilometers and a population of 625000. Siping has jurisdiction over Tiedong District, Tiexi District, Gongzhuling City, Shuangliao City, Lishu County and Yitong County. Siping has a long history, and the site of the ancient city of Yan on the bank of Erlong Lake, 50 kilometers away from the urban area, is the witness of the Han nationality's earliest development of Northeast China. History has left cultural monuments such as Hanzhou in Liao Dynasty, Xinzhou in Jin Dynasty and Yehe Tribe in Ming Dynasty. Daqingshan Village cultural sites, Yehe ancient city ruins, Liao and Jin dynasties