YIN MOUNTAINS

Wade-Giles and Pinyin romanization Yin Shan, range in the Inner Mongolian autonomous ch' (region), China, comprising the Ta-ch'ing, Wu-la, Hara-narin, Sheyten, and Lang mountains. The Yin Mountains mostly rise to heights of about 6,500 feet (2,000 m). The highest peaks in the southwestern Ta-ch'ing Mountains reach 7,175 feet (2,187 m). The subranges run roughly east to west along the northern bend of the Huang Ho (Yellow River) to the north of the Ordos Desert. They are sharply tilted, presenting a sharp and abrupt southern slope, and a gentle northern slope that merges into the high plateau of the Gobi (desert) to the north. The southern slope drains into the Huang Ho proper or into its tributaries, the Ta-hei River to the east and the Wu-chia River in the west. The northern slopes drain northward into the desert; two of the longest of the northward-flowing streams are the Hsi-la-mu-lun River (Mongolian Shira Muren) and Ai-pu-kai River. The Yin ranges as a whole are mostly composed of ancient metamorphic rocks, but particularly in the southern ranges of the Wu-la and Ta-ch'ing mountains there are thick sedimentary rocks. These include rich coal beds, and large coal mines are in operation at Shih-kuai-kou to supply power stations as well as the giant iron and steel complex at nearby Pao-t'ou, which also draws its supplies of iron ore from the northern part of the Yin Mountains at Pai-yn-o-po. Most of the Yin range is arid, particularly in the western ranges, such as the Lang Mountains. In the central and eastern districts the climate is more moist; the vegetation is mostly grassland, with some trees such as birch and elm.