Northern China forms an integral part of the north temperate zone of the Old World. It is, moreover, connected with western Asia and eastern Europe by a long but continuous belt of steppe presenting no transverse barriers to migration, whether faunal or human. It cannot, therefore, be treated as a region apart, save in a very limited and subordinate sense.
The surface consists in the main of mountains in the west and of plains in the east. Over much of it lie thick deposits of loess, extending from Chinese Turkistan right across eastern Asia, nearly to the Yellow Sea. These great accumulations of wind-borne soil were most probably formed during times roughly contemporary with the Riss-Wurm glaciation of Europe.