Volcanic Rocks.—Amongst the Archean rocks granitic and other intrusions are abundant, but of more modern volcanic activity the remains are comparatively scanty. In south China there is no evidence of Tertiary or Post-Tertiary volcanoes, but groups of volcanic cones occur in the great plain of north China. In the Liao-tung and Shan-tung peninsulas there are basaltic plateaus, and similar outpourings occur upon the borders of Mongolia. All these outbursts appear to be of Tertiary or later data.
Loess.—One of the most characteristic deposits of China is the loess, which not merely imparts to north China the physical character of the scenery, but also determines the agricultural products, the transport, and general economic life of the people of that part of the country. It is peculiar to north China and it is not found south of the Yangtsze. The loess is a solid but friable earth of brownish-yellow colour, and when triturated with water is not unlike loam, but differs from the latter by its highly porous and tubular structure. The loess soil is extremely favourable to agriculture. (See [Loess] and infra, § Agriculture.)
The loess is called by the Chinese Hwang-t‘u, or yellow earth, and it has been suggested that the imperial title Hwang-ti, Yellow Emperor or Ruler of the Yellow, had its origin in the fact that the emperor is lord of the loess or yellow earth.
Structurally, China proper may be divided into two regions, separated from each other by the folded range of the Tsing-ling-shan, which is a continuation of the folded belt of the Kuen-lun. North of this chain the Palaeozoic beds are Structure. in general nearly horizontal, and the limestones and sandstones of the Sinian and Carboniferous systems form an extensive plateau which rises abruptly from the western margin of the great plain of northern China. The plateau is deeply carved by the rivers which flow through it; and the strata are often faulted, but they are never sharply folded. South of the Tsing-ling-shan, on the other hand, the Palaeozoic beds are thrown into a series of folds running from W. 30° S. to E. 30° N., which form the hilly region of southern China. Towards Tongking these folds probably bend southwards and join the folds of Further India. Amongst these folded beds lie trough-like depressions filled with the Mesozoic red sandstone which lies unconformably upon the Palaeozoic rocks.
The present configuration of China is due, in a very considerable degree, to faulting. The abrupt eastern edge of the Shan-si plateau, where it overlooks the great plain, is a line of fault, or rather a series of step faults, with the downthrow on the east; and von Richthofen has shown reason to believe that this line of faulting is continued far to the south and to the north. He believed also that the present coast-line of China has to a large extent been determined by similar faults with their downthrow on the east.
Concerning the structure of the central Asian plateau our knowledge is still incomplete. The great mountain chains, the Kuen-lun, the Nan-shan and the Tian-shan, are belts of folding; but the Mongolian Altai is a horst—a strip of ancient rock lying between two faults and with a depressed area upon each side. In the whole of this northern region faulting, as distinct from folding, seems to have played an important part. Along the southern margin of the Tian-shan there is a remarkable trough-like depression which appears to lie between two approximately parallel faults.
(P. La.)
Fauna.
China lies within two zoological provinces or regions, its southern portion forming a part of the Oriental or Indian region and having a fauna close akin to that of the western Himalaya, Burma and Siam, whereas the districts to the north of Fu-chow and south of the Yangtsze-kiang lie within the eastern Holarctic (Palaearctic) region, or rather the southern fringe of the latter, which has been separated as the Mediterranean transitional region. Of these two divisions of the Chinese fauna, the northern one is the more interesting, since it forms the chief home of a number of peculiar generic types, and also includes types represented elsewhere at the present day (exclusive in one case of Japan) only in North America. The occurrence in China of these types common to the eastern and western hemispheres is important in regard to the former existence of a land-bridge between Eastern Asia and North America by way of Bering Strait.
Of the types peculiar to China and North America the alligator of the Yangtsze-kiang is generically identical with its Mississippi relative. The spoon-beaked sturgeon of the Yangtsze and Hwang-ho is, however, now separated, as Psephurus, from the closely allied American Polyodon. Among insectivorous mammals the Chinese and Japanese shrew-moles, respectively forming the genera Uropsilus and Urotrichus, are represented in America by Neurotrichus. The giant salamander of the rivers of China and Japan and the Chinese mandarin duck are by some included in the same genera as their American representatives, while by others they are referred to genera apart. Whichever view we take does not alter their close relationship. One wapiti occurs on the Tibetan frontier, and others in Manchuria and Amurland.