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.
Xinghai County is located in the southwest of Hainan Tibetan Autonomous Prefecture of Qinghai Province, and is located in the core area of national nature conservation of "Sanjiangyuan". The county has a total area of 12100 square kilometers, facing Guinan and Tongde across the Yellow River in the east, Gonghe County in the north, Dulan County in Hercynian Mongolian and Tibetan Autonomous Prefecture in the west, and Maduo County and Maqin County in the south. It is 248 kilometers away from Xining, the capital of Hainan Tibetan Autonomous Prefecture, and 103 kilometers away from Qiabu, capital of Hainan Tibetan Autonomous Prefecture. The geographical coordinates are 34 °48 degrees north, 36 degrees 14 degrees north and 99 degrees 01 degrees east, 100 degrees 59 'east. The average elevation of Xinghai County is 3924 meters (Ziketan Town, where the county government is located, is 3303 meters above sea level). Although the highest point of the Ela Mountains is 5305 meters above sea level in Genergang, the lowest point is 2590 meters above sea level at the exit of the Yellow River in Heka Town. Full