Basic characteristics of China landform

A remarkable feature of China's landforms is the formation of three-level landforms. The first level is the Qinghai-Tibet Plateau, with an average elevation of 4,000-4,500 m, a dry and cold climate, a well-developed glacier and frozen soil landform, a relatively undulating surface, and strong cutting at the periphery. The second step is the Loess Plateau-Yunnan-Guizhou Plateau, with an altitude of1500 ~ 2000 m. The river valley is deep, and the surface fluctuation is larger than that of the first step. The climate is dry and cold in the north and warm and humid in the south, which is characterized by the development of river landform and sandstorm landform. The third level is the eastern plain-southeast hills, with low altitude, small topographic relief, humid climate and developed rivers and lakes.

2. Diversity of landform types and causes

Because of China's complicated geographical environment, diverse climatic types and changeable geomorphological driving forces, there are many geomorphological types in China. There are not only volcanic landforms and structural landforms formed by internal dynamics, but also river landforms, karst landforms, glacial landforms, frozen soil landforms, aeolian landforms, coastal landforms, lakes and swamps, such as the Beijing-Hangzhou Grand Canal and terraces.

3. Regional development of landforms

The regional characteristics of China landform development are also very obvious, which are zonal, meridional and highly zonal. In the latitude direction, the main landforms developed from south to north are brick red soil weathering crust-karst and river landform-river and lake landform-aeolian landform-frozen soil landform. In the meridian direction, from east to west, it is coastal landform-river and lake landform-loess landform-desert (rapids landform)-gravel desert. In the height division, from low to high, it is coastal landform-river and lake landform-aeolian landform-frozen soil landform-glacier landform.

4. The periodicity of landform development

The development of geomorphology is closely related to tectonic movement, and there is a certain causal relationship between them. Tectonic movement affects the formation and development of geomorphology, which in turn reflects the characteristics of tectonic movement. The stage of neotectonic movement in China is obvious, and the active period and relative quiet period appear alternately, resulting in the geomorphic stage and geomorphic cycle of geomorphic evolution in China.

As early as the beginning of the 20th century (1904), when Willis studied the Quaternary geology and geomorphology of North China, he put forward the geomorphological stage of the development of North China (Table 2- 14). The so-called landform period refers to the stage of landform formation and development. Geomorphological period is a manifestation of geomorphological development cycle, which is characterized by alternating accumulation or leveling with erosion or cutting. The karst areas in southern China have also been divided into a series of karst periods (Table 2- 14).

Table 2- 14 Comparison of Geomorphological Development in China

Think about a problem

1) Why are there many schemes to divide the quaternary lower limit? What do you get from it?

2) Why is the landform and Quaternary geology of China unique? What impact does it have on today's human living environment?

3) What is the significance of studying the Quaternary glacial and interglacial periods?

4) What are the dynamic factors of landform evolution and development? What's the significance of Davis's geomorphological evolution theory?