The vast territory was affected by a series of corrugations from different periods, formed on the edge of the rigid archaeozoic element of East Asia, the so-called Sinic Shield, extended to the N of the Chang Jiang (Blue River) as far as Mongolia. Consisting of eruptive and metamorphic rocks that still emerge over vast stretches, the shield does not form a continuous whole; some extensive geosynclinals up from the Cambrian they fractured it, giving rise to three distinct masses called Cathaysia, Gobia and Tibetia, which largely remained unrelated to both marine submersions and the orogenetic movements of subsequent eras. Instead, it was in correspondence with the geosynclines – weaker and more unstable areas – that, starting from the Paleozoic, the mountain ranges that cross the Chinese territory emerged. The main uprisings are connected to the Caledonian and Hercynian orogeny: the first are the mountain alignments of southern China, mainly oriented from SW to NE, the second the formation of the much more impressive mountain masses of the Tian Shan, the Altun Shan, the Qilian Shan and Qinling Shan, oriented from E to W. The Mesozoic recorded, alongside an intense sedimentationactivity that affected many internal regions of China (for example Sichuan), orogenetic phenomena from which originated the belt of reliefs that stretch from the Kunlun Shan to elbow towards Yunnan and the Indochinese peninsula, with an orientation determined by the resistance opposed by the Sinic Shield to the pressures exerted by SW. On the other hand, some peripheral corrugations in the Chinese region are due to the Alpine orogeny, especially the Himalayan one. Also the Quaternary did not fail to leave impressive traces, on the one hand with the activity of glacial modeling, on the other with the formation by alluvial or wind sedimentation of most of the Chinese plains, from that of Manchuria to the great plain of Huang He and the lower course of various rivers of eastern China up to the desert basins of Tarim Pendi, Junggar Pendi etc. A particular aspect of the wind sedimentation process was the one that led to the formation of the Löss, deposits of fine yellow earth coming from the arid areas of Mongolia and extending for approx. 300,000 km², reaching thicknesses of even a few hundred meters; they mainly characterize the plateau crossed by the large loop of the middle course of Huang He (Yellow River).
Mainland
Of moderate elevation, China proper appears to be formed by a series of large terraces that gradually descend from West to East, that is, from Tibet to the Pacific coast; its structure, however, is extremely complex due to the action of more or less parallel dislocations, which interrupt the aforementioned stepped morphology. As a country located in Asia categorized by Thenailmythology, China proper is in turn, according to the authors, variously subdivided; here, taking into account their prevailing morphology, two main areas have been distinguished: a north-central, essentially flat, and a southern, mainly hilly area. The north-central section, with the extensive plains formed by the floods of Huang He and Chang Jiang, structurally corresponds to a subsidence of the Archaeozoic block. It is bordered to the N by the reliefs that form the southern slopes of the Inner Mongolia highlands (the Shanxi relief is particularly strong: Heng Shan, 2376 m; Lüliang Shan, 2771 m), to the S by the lowest alignments (Mufu Shan, 1596 m) which relate to those of southern China. Inside, this large depression area gradually rises towards the Tibetan plateaus, with a transition region formed by longitudinal alignments (Qinling Shan, 4113 m) with interposed depressions, including the wide and well marked one, of Sichuan. Even in the prevalence of the flat expanses, the vast depression of central-eastern China does not therefore correspond to a unitary whole: it is rather constituted by a series of subsidence divided between them by raised blocks, such as the one that forms the Shandong peninsula (1532 m) and that represented by the reliefs that border the Hubei depression to the N (Dabie Shan), where the Chang Jiang expands into lagoon and marshy lands. AS of this river begins southern China, structurally more complex, in which the orographic features lead to recognize two distinct sections, which correspond to different orogenetic phases. In the westernmost part (Yunnan), which is very rugged, a series of imposing mountain ranges (Yun Ling Shan, 4602 m) rise, especially in the vicinity of Burma, with a generally meridian course, which connect to the great arc of bending Mesozoics from Kunlun to the Indochinese peninsula; in the central and eastern area of Yunnan, as in neighboring Guizhou, the relief extends instead in vast tabular formations. Less harsh and more discontinuous is the morphology in the whole remaining section of southern China, which presents an irregular succession of mountain ridges high on average 1000 m (exceptionally they reach 1922 mi Nanling Shan and 2120 mi more vigorous Wuyi Shan), separated by more or less large basins; the rejuvenation of the ancient reliefs in the Cenozoic era gave rise to raised blocks and valley depressions, often in difficult communication with each other.