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The Ordos () Loop is a region of China west of Beijing. ==Geographic characteristics== The Yellow River flows north-northeast, then east, and then south, forming three sides of an imperfect rectangle. The south side is formed by the Wei River, which rises not far from the southwest corner and flows east to the southeast corner. Clockwise from the southwest corner, the sides of the 'rectangle' are about 640, 320, 600, and 560 kilometers. At the southeast corner, the Yellow River turns east and finds its way through the mountains at the Hangu Pass onto the North China Plain. Rainfall and therefore population decreases rapidly as one moves north. The Wei River valley on the south is densely populated and is one of the ancient centers of Chinese civilization. The north is grassland and desert (Ordos desert) and is part of Inner Mongolia. The Great Wall of China cuts across the center roughly separating the nomadic north from the agricultural south. The Ordos region proper is the area north of the wall. Although this rectangular area is obvious on a map, the north and south are so different that the region cannot be said to have a common history. To the south of the Wei valley are the high Qin Mountains which separate it from the valley of the Han River, a tributary of the Yangtze River. Further south and somewhat west is the Sichuan basin. To the east are the Lüliang Mountains which form the west side of the Shanxi Plateau. To the north and northwest are the grasslands of Inner Mongolia. The southwest corner merges into the Tibetan Plateau. An ancient tradition says that the Chinese people entered China by travelling down the Wei River. By about 1000 BC Chinese civilization was centered on the west side of the North China Plain with an extension up the Wei valley and a northern extension up the Fen River. The lower Wei valley is still one of the most densely populated areas in China. Rulers based in the Wei valley had an advantage since the mountains to the east made a natural fortification and war horses were readily available from the northern grasslands. The Zhou dynasty and the Qin dynasty started in the Wei valley. Xi'an on the lower Wei was several times the capital of China. By the Tang dynasty the economic center of China had shifted to the Yangzi valley and the Wei region became partly dependent of food imported up the Grand Canal. To the north of the Wei valley is the Loess Plateau with its many gullies and cave houses. It is loess from this region that makes the Yellow River yellow. Because of its low and variable rainfall the region was once notorious for drought and famine. Underlying the loess plateau is one of the largest coal beds in China. North and west of the loess plateau the grassland and desert belongs historically and culturally to Mongolia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ordos Loop」の詳細全文を読む スポンサード リンク
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