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.
Tongguan County, which belongs to Weinan City, Shaanxi Province, is located at the eastern end of Guanzhong Plain in Shaanxi Province. It is bordered by Lingbao City, Henan Province in the east, Huayin City in the west, Luonan County in the south, Dali County in the northwest, and Ruicheng County in Shanxi Province across the Yellow River in the north. It is between longitude 110o 090032 "- 110o 25027" east and latitude 34o 230033 "- 34o 390001" north, with a total area of 526 square kilometers. In 2018, Tongguan County had a resident population of 154200, with a regional gross domestic product (GDP) of 4.035 billion yuan, of which the added value of the primary industry was 484 million yuan, the secondary industry was 1.446 billion yuan, the tertiary industry was 2.104 billion yuan, and the primary, secondary and tertiary industries accounted for 12.0% and 35.8% of the GDP, respectively.