A fertile layer of windblown silt gave northern China its nickname, “The Land of the Yellow Earth.” Everything is yellow. The hills, the roads, the fields, the water of the rivers and brooks are yellow … even the atmosphere is seldom free from a yellow haze It was thus that the geologist Baron Ferdinand von Richthofen (the father of Germany’s World War I flying ace) described the extraordinary landscape of Shansi Province in north-central China in the 1870′s. The scene remains much the same today.
The Shansi Loess Region is just a part of a much more extensive area of similar landscapes in the middle part of the Yellow River basin in northern China. Its distinctive look results from deep deposits of a yellow loosely packed, fertile type of soil known as loess. The name, derived from a German word meaning “to loosen:’ was originally applied to a similar soil in the Rhine Valley. Great quantities of loess are also found in the Mississippi Valley, Central Asia, and many other areas. But in few places in the world is it so deep and widespread as in this part of China. Besides being highly fertile, this fine-grained type of soil also holds together well enough to form vertical cliffs and support the roofs of caves. In the Shansi region, in fact, farmers have traditionally lived in caves beneath their fields. An unexpected result is the sight of plumes of smoke rising from their hearth fires and escaping through shafts dug in their grainfields overhead.
Loess is also susceptible to severe erosion. The Shansi Loess Region is crisscrossed by networks of deep gullies and ravines that grow in length and depth with each rainfall. Ultimately the eroded soil is carried into the Yellow River, making its water even yellower. The Yellow carries so much sediment, derived for the most part from the loess region, that it is the muddiest river in the world.
The loess itself consists of extremely fine-grained particles of quartz, mica, feldspar, calcite, and other materials, mixed with clay dust. At one time it was believed that all loess originated as strictly windblown deposits of these silty particles. Many geologists now believe, however, that other processes were also involved. Water, for example, probably played a significant role in both rearranging and weathering the material.
Whatever the case may be, it is agreed that the loess accumulated over at least the last 3 million years. The deposits in the Shansi region, which in places are hundreds of feet deep, were probably blown in from the Ordos and Gobi deserts, situated just to the northwest Similarly, the loess of the American Midwest consists of deposits blown in from regions where finely scoured glacial debris was freed by the melting of the continental ice cap during the Ice Age. Sarah writes the Prague guide and writing about travel.