Loess Plateau

Loess Plateau 

a natural region in China, in the middle part of the Huangho basin. It is bounded in the south by the Ch’inling Range, in the east by the T’aihang Shan, in the north by the Ordos Desert, in the northwest by the Ala Shan Desert, and in the west by the eastern spurs of the Kunlun. Area, about 430,000 sq km; prevailing altitudes, 1,200–1,500 m. Within the Loess Plateau there are individual ranges (Luip’an Shan, Luiliang Shan, Wut’ai Shan), whose crests in places reach 2,500 m and more.

In geological terms the Loess Plateau is a basin filled with a thick layer of Mesozoic deposits overlain by loess. The thickness of the loess usually varies from 100 to 200 m, increasing in the north to 250 m. The friable series of loess are subject to intense erosion. In certain regions the network of ravines reaches 5–6 km per sq km, with a depth of 100–150 m. In the north there is a predominance of loess ridges and spurs extending in the direction of the prevailing winds and with an overall depth of up to 300–400 m. In the south, flat and rolling plateaus cut by ravines have developed.

The climate is temperate with dry cold winters and hot summers. The average January temperature is from— 8°C in the north to— 4°C in the south, and for July from 22°C in the north to 24°C in the south. Precipitation totals from 500 mm per year in the east to 250 mm in the northwest. Most of it falls during the summer monsoon (July to September), usually as downpours that further the development of erosion.

The rivers often flow in deep gorges and carry an enormous amount of detritus. The annual volume of solid drainage in the Huangho below the Loess Plateau exceeds 1.3 billion tons. The soils on the loess are characterized by high fertility, but in their majority they are eroded. Natural vegetation—forest steppe in the southeast and arid steppe in the northwest—has survived only in places unsuitable for agriculture. The entire surface has been plowed up, and loess slopes up to 1,000 m in elevation and more have been artificially terraced. Cotton, millet, kaoliang, and wheat are grown. There are deposits of hard coal, iron ore, oil, combustible shale, gypsum, and salt. The Loess Plateau (particularly the Wei River valley) is densely populated. The major cities are Hsian, T’aiyüan, and Lanchou.

V. T. ZAICHIKOV