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.
Lankao, a county under the jurisdiction of Kaifeng City, Henan Province, and Zhiguan County, Henan Province, is located at the last bend of the Jiuqu Yellow River, with a total area of 1116 square kilometers and a total population of 859100. It is an important part of "half-hour traffic circle" in "one pole, two circles and three layers" in Henan Province. Lankao County was a household in the Spring and Autumn period, and Jiyang County was the beginning of Lankao County in the Qin Dynasty. In 5 BC, Emperor Liu Xiu, Emperor of the Han Dynasty, was born in the Jiyang Palace in the north of the county. In 9 years, it was changed from Dongfen County to Dongming County. In 1218, Dongming County was abandoned as Tongan Castle, and the new county seat was moved to the old land of Yuanggu County in the north of the Yellow River. In 1232, the south of the Yellow River was divided into two counties: Lanyang County and Yifeng County. In March 1783, the county seat of Kaocheng County moved to Lankao County for the first time. In 1825, Yifeng County was merged into Lanyang County, known as "Lanyi County".