China

The North China Plain

Comparable in size to the Northeast Plain, most of the North China Plain lies at elevations below 160 feet (50 metres), and the relief is monotonously flat. It was formed by enormous sedimentary deposits brought down by the Huang He and Huai River from the Loess Plateau; the Quaternary deposits alone (i.e., those from the past 2.6 million years) reach thicknesses of 2,500 to 3,000 feet (760 to 900 metres). The river channels, which are higher than the surrounding locality, form local water divides, and the areas between the channels are depressions in which lakes and swamps are found. In particularly low and flat areas, the underground water table often fluctuates from 5 to 6.5 feet (1.5 to 2 metres), forming meadow swamps and, in some places, resulting in saline soils. A densely populated area that has long been under settlement, the North China Plain has the highest proportion of land under cultivation of any region in China.