Chinese terrain

Author: Shen Shian
Publisher:
Publish Date: 2001-10-01
Features: The topography of China is characterized by the following aspects:
1. West-high and east-low, with a step-like distribution: The Yellow River and Yangtze River, rolling and surging, originate from the Qinghai-Tibet Plateau in the west and flow eastward through nine or ten provinces, municipalities, and autonomous regions before emptying into the Bohai Sea and the East China Sea. The general flow of China's major rivers reflects the overall topographic trend of west-high and east-low. China's terrain is not only west-high and east-low but also various topographic types are roughly arranged around the Qinghai-Tibet Plateau, known as the "Roof of the World," in a semi-circular step-like manner toward the Pacific Ocean. The terrain boundary formed by two mountain ranges distinctly divides the continental terrain into three steps. The Qinghai-Tibet Plateau has an average elevation of over 4,000 meters and covers an area of 2.3 million square kilometers, making it one of the largest plateaus in the world and the highest step in China's topography. It dominates the southwest, with a series of snow-capped mountain ranges stretching across the plateau from north to south, including the Kunlun Mountains, Altun Mountains, Qilian Mountains, Tanggula Mountains, Karakoram Mountains, Gangdise Mountains, and Himalayas. Between the mountain ranges of the plateau are numerous large and small basins with rich grasslands and shimmering lakes. Here, abundant resources are stored, awaiting our exploitation and development.
Beyond the northern edge of the Qinghai-Tibet Plateau along the Kunlun Mountains-Qilian Mountains and the eastern edge along the Min Mountains-Qionglai Mountains-Hengduan Mountains, the terrain drops rapidly to an altitude of about 1,000 to 2,000 meters, with some local areas below 500 meters—this is the second step. Its eastern boundary roughly extends from the Greater Khingan Mountains to the Taihang Mountains, then southward through the Wushan Mountains to the Wuling Mountains and Xuefeng Mountains. Here, a series of high mountains, plateaus, and basins above 1,500 meters in altitude are distributed, including the Altun Mountains, Tian Shan Mountains, Qinling Mountains; the Inner Mongolian Plateau, Loess Plateau, and Yunnan-Guizhou Plateau; the Junggar Basin, Tarim Basin, Qaidam Basin, and Sichuan Basin. Beyond the Greater Khingan Mountains to the Xuefeng Mountains eastward to the coast lies a region of hills and plains below 500 meters in altitude, which can be considered the third step. In this step, from north to south, there are the Northeast Plain, North China Plain, and Middle-Lower Yangtze Plain; to the south of the Yangtze River, there is a vast area of low mountains and hills generally referred to as the Southeast Hills. The former are mostly below 200 meters in altitude, while the latter are mostly between 200 and 500 meters, with only a few mountain ranges reaching or exceeding 1,000 meters. From the coastline eastward lies an endless expanse of shallow seas with inadequate depths of less than 200 meters, dotted with islands—this is also sometimes referred to as the fourth step of China's topography.
In terms of landforms, two boundaries and three steps gradually descend from west to east, roughly outlining the overall outline of China's topography. This step-like topographic pattern is reflected in the topographic profiles along China's 89° east longitude and 30° north latitude. China's topographic characteristics of being west-high and east-low, facing the ocean with gradual descent, not only facilitate the penetration of warm and humid maritime airflows from the southeast into the interior, profoundly influencing China's climate in a positive way but also allow China's major rivers to flow eastward into the sea. This not only facilitates maritime-continental transportation in China but also eases economic and trade exchanges between China's eastern and western regions. At the same time, this step-like topography also influences rivers to form significant multi-step drops, thereby storing enormous hydropower resources that are favorable for multi-level development.
2. Diverse Morphology, Vast Mountainous Areas
China's topographic types are diverse and rich in variety, whether viewed from their formation or morphology. There are high plateaus and mountains uplifted by internal forces, as well as low-lying basins and plains subsided by folding. In the warm and humid eastern and southern regions, there are various erosion and deposition landforms dominated by fluvial processes; in the arid northwest, there are desert landscapes dominated by wind action; on the western high mountains, there are distinctive glacial landforms; and in the southwestern limestone distribution areas, there are scenic karst landscapes. The Qinghai-Tibet, Yunnan-Guizhou, Inner Mongolian, and Loess Plateaus are China's four famous plateaus. The Tarim, Junggar, Qaidam, and Sichuan Basins are China's four famous basins. Major rivers such as the Yangtze, Yellow River, Pearl River, and Heilongjiang flow across the vast land, creating many extensive and fertile plains. On these plains are lush and beautiful low mountains and hills, while in the west there are countless towering and rugged mountains. Diverse topography provides extremely favorable conditions for the comprehensive development of agriculture, forestry, animal husbandry, sideline industries, and fishery industries. Statistics show that mountains and hills account for about 43% of China's total land area, plateaus for 26%, basins for 19%, and plains for 12%. If high mountains, medium mountains, low mountains, hills, and rugged plateaus are all included, then the area of mountainous regions in China accounts for more than two-thirds of the total land area. Although mountainous areas are not conducive to the development of agriculture, transportation, and economic and cultural exchanges, they are rich in mineral resources, dense forests, and precious plant and animal resources, all of which are invaluable assets for China's socialist construction.
3. Interweaving Mountain Ranges with Oriented Arrangement
China is a mountainous country, not only with vast mountainous areas but also with large and small mountain ranges crisscrossing the nation in an orderly and oriented arrangement, primarily in east-west and northeast-southwest directions, with fewer in northwest-southeast and north-south directions. The east-west mountain ranges consist of three major rows: the northernmost is the Tian Shan-Yinshan, the middle is the Kunlun Mountains-Qinling Mountains, and the southernmost is the Nanling Mountains. The northeast-southwest mountain ranges are mostly distributed in the east, with lower elevations, and there are also three major rows of these: the westernmost is the Greater Khingan Mountains-Taihang Mountains-Wushan Mountains-Wuling Mountains-Snow Peak Mountains, which is the boundary between the second and third steps mentioned earlier; the middle row includes Changbai Mountains, Liaodong Hills, Shandong Hills, and the southeastern hills in Zhejiang and Fujian; the easternmost row is the Taiwan Mountains rising from the sea. The northwest-southeast mountain ranges are mostly distributed in the west, in order from north to south: Altun Mountains, Qilian Mountains, and Himalayas. The north-south mountain ranges run through the central part of China, mainly including the Helan Mountains, Liupan Mountains, and Hengduan Mountains. These mountain ranges form the skeleton of China's topography, dividing the land into many grids. The outlines of plateaus, basins, plains, inland seas, and marginal seas within these grids are constrained to some extent by these mountain ranges. The east-west mountain ranges across the country also serve as water divides for major rivers. The Qinling Mountains are the water divide between the Yellow River and the Yangtze River, while the Nanling Mountains are the water divide between the Yangtze River and the Pearl River. The flow of rivers is clearly influenced by mountain ranges, such as the Yarlung Zangbo River, Jinsha River, Lancang River, and Nujiang River in the southwest, all of which are controlled by mountain ranges such as the Gangdise Mountains, Tanggula Mountains, Himalayas, and Hengduan Mountains. The overall flow of the Yangtze and Yellow Rivers is from west to east, but many sections are also constrained by mountain ranges, alternating between widening and narrowing, sometimes flowing southeastward and sometimes northeastward, ultimately emptying into the sea.
In addition to these three major characteristics, from a structural perspective, China's topographic features can be summarized in four aspects: three longitudinal mountain belts, three marginal Pacific mountain ranges, two large-scale depressions with specific orientations, and one large arcuate mountain range.
The three longitudinal mountain belts refer to the three east-west mountain systems mentioned earlier, with intervals of almost 8 to 10 degrees of latitude. For example, the main body of the Tian Shan-Yinshan is roughly located between 40°30′N and 42°30′N; the main body of the Kunlun Mountains-Qinling Mountains is roughly between 32°30′N and 34°30′N; and the main body of the Nanling Mountains is roughly between 24°00′N and 25°30′N. These three longitudinal mountain belts actually form three important geographical boundaries in China, which have a significant impact on China's climate, hydrology, and agricultural production.
The three marginal Pacific mountain ranges refer to the three northeast-southwest mountain ranges in eastern China, which are almost three parallel belt-like mountain ranges: the easternmost is the Taiwan Mountains, the middle is the Changbai Mountains-Zhejiang-Fujian hills, and the westernmost is the Greater Khingan Mountains-Snow Peak Mountains. Since their positions are almost perpendicular to China's prevailing southeast monsoon, they enhance the climatic characteristics of humid eastern China and arid western China. This effect is particularly evident in the Greater Khingan Mountains, where erosion prevails to the east of the range, while dry denudation dominates to the west.
The two large-scale depressions with specific orientations refer to the northeast-southwest trending subsidence belts in eastern China formed by the Northeast Plain, North China Plain, and Middle-Lower Yangtze Plain, as well as the other subsidence belt in the central part of China formed by the Hulunbuir Basin, Shaanxi-Gansu-Ningxia Basin, and Sichuan Basin, both located west of the Greater Khingan Mountains. The sides of these subsidence belts are corresponding uplift belts. In northwestern China, there is another group of three large basins nearly east-west trending: the Junggar Basin, Tarim Basin, and Qaidam Basin, which are roughly parallel to the east-west mountain systems and also reflect the alternating characteristics of subsidence belts and uplift belts. This alternating pattern of subsidence belts and uplift belts further illustrates the internal connections between different topographic features, indicating that subsidence and uplift, depression and uplift are a pair of opposing yet complementary contradictions in nature. The existence and discovery of this phenomenon have great practical significance. Because in the Xinaoxia system subsidence belts and uplift belts in eastern China, many basins separated by east-west structural systems are ideal oil-bearing basins. As early as the 1950s, Li Siguang, based on the theory of geomechanics, pointed out that these subsidence belts definitely contained oil and proposed that the Songliao Plain, North China Plain, Sichuan Basin, and Shaanxi-Gansu-Ningxia Basin were promising areas for oil exploration. Li Siguang's scientific conclusion has been verified by practice.
The large arcuate mountain range mainly refers to the mountain belt in the southwest formed by the Himalayas, Gangdise Mountains, Tanggula Mountains, Daxue Mountains, and Hengduan Mountains, which rise majestically above the Qinghai-Tibet Plateau, forming the most magnificent and towering mountain belt in the world. The formation of this high mountain belt is mainly due to the collision of the Indian subcontinent's continental crust with the Asian continent, and the sliding of the continental basement along it. As a result, the Qinghai-Tibet Plateau has been gradually uplifted and clearly exhibits the thickness of two continents. This concept has been supported by seismic evidence.
Huaxia tectonics and Xinaoxia tectonics are names of tectonic systems within the twisting tectonic system of geomechanics. The Huaxia tectonic system is a set of compression zones close to 45° northeast. The Xinaoxia tectonic system is a set of compression zones in a north-northeast direction, widely distributed in eastern China, forming three uplift belts and three subsidence belts from east to west, essentially a large-scale multi-character tectonic system.