There are five famous basins in China, namely, Sichuan, Tarim, Turpan, Junggar and Qaidam, covering an area of over 654.38 million square kilometers. Tarim Basin, Junggar Basin, Qaidam Basin and Sichuan Basin are also called "China Four great basin".
Tarim Basin
Tarim Basin, located in the south of Xinjiang, is the largest basin in China. "Tarim Basin" is a Chinese translation of Uygur language, which means "great basin without reins". The basin starts from Pamir Plateau in the west and reaches the junction of Gansu and Xinjiang in the east. It is about 1.600 km long from east to west and 600 km wide from north to south, covering an area of about 530,000 square kilometers, with an average elevation of about 1.000 m, accounting for about half of the total area of Xinjiang. It is 2.6 times larger than Sichuan Basin, 1.4 times larger than Junggar Basin in northern Xinjiang and 10 times larger than Turpan Basin, making it the largest inland basin in China.
Tarim basin is located in the hinterland of Eurasia, and the surrounding mountains are all at an altitude of 4000 ~ 6000 meters. It is far from the sea, with dry climate and little rain, large temperature difference between day and night, and great seasonal changes. It is a typical continental desert climate. It's cold in winter and hot in summer. 1 Monthly average temperature-10℃, and July average temperature is 25℃. The temperature difference between winter and summer in the same place can reach 50℃-60℃, and the temperature difference between day and night can reach 15℃-20℃. Whenever it is cold at the turn of spring, summer, autumn and winter, I often wear cotton-padded clothes; The temperature is very high at noon, and it is still hot in light clothes. So people use "wearing fur coats in the morning, tulle in the afternoon and eating watermelons by the fire" to describe the climate characteristics here. Rainfall in most areas of the basin is less than 50 mm, and in the east it is only about 10 mm, and in some places it doesn't even drop all year round.
Gobi desert, alluvial fan plain and sand dune area appear in turn from the edge of the basin to the center, and the whole basin is in a ring structure. Alluvial plains formed by rivers in the surrounding mountains are usually oases. The oases are Kashgar, Dongsha, Hotan, Aksu and Kuqa. Oasis agriculture is developed, canals are vertical and horizontal, fields and buildings are connected, trees are shaded, and wheat, corn, rice, cotton and fruits are abundant. This is an important grain, long-staple cotton and silk producing area in China. The central part of the basin is the largest Taklimakan desert in China, with an area of about 334,000 square kilometers, which is also a world-famous desert. Because of the large desert area and extreme water shortage, few people in the old society could enter the central area of the desert, so this big desert was named "Taklimakan", which means Uygur, because it was impossible to get in and out. There is a famous wandering lake in the east of the basin-Lop Nur. There are also many inland rivers, the water source is not from rain, but mainly from melting snow in the mountains.
The people living in Tarim Basin are mainly Uighurs. In the old society, due to various reasons such as inconvenient transportation, it was naturally closed and few people came. After liberation, with the progress of society and the development of science, the communication between people has been accelerated, and the number of people coming here is increasing day by day. In particular, the people's government has sent scientific investigation teams here many times to inspect natural conditions and resources, and found that there are not only rich mineral resources, but also a variety of non-ferrous metals and oil, as well as a large number of salt mines. With the development of China's construction, these precious resources will be rationally developed and utilized.
Junggar Basin
Junggar Basin is located at the northern foot of Tianshan Mountain, between Tianshan Mountain and Altai Mountain, surrounded by mountains in the northwest, northeast and south, forming an equilateral triangle with an area of about 380,000 square kilometers. It is the second great basin in China. The topography of the basin is slightly inclined from east to west, and the elevation of the eastern end can reach 1000 meters, while the lake depression in the west has dropped to 200-400 meters, and the water level of Ebinur Lake is only 189 meters, which is the lowest place in the basin.
The topographic structure of Junggar basin is similar to that of Tarim basin, but there are many gaps in the surrounding mountains, so the shape of the basin is not as complete as that of Tarim basin. The east and west ends of the basin are relatively developed, which has become the channel for China to Central Asia. The average elevation of the basin is about 500 meters, and the terrain gradually increases eastward, which is connected with the Inner Mongolia Plateau. The scenery inside the basin is very complicated, including grasslands, deserts, salt lakes and swamps. Among them, the desert is limited to the central and eastern part, that is, the east of Manas River, which is collectively called Gurbantunggut Desert. The climate here is dry, and the sand dunes are relatively small and low in height. There is more precipitation in the west of Manas River, mostly in grassland and swamp areas. There are mountains as high as 2000 meters in the west of the basin, but there are several gaps. The northwest wind blows into the basin, and the climate is cold in winter.
Junggar basin is rich in oil, coal and various metal deposits. Karamay in the west of the basin is one of the larger oil fields in China. The northern area of Altai Mountain has been famous for its rich gold since ancient times. There are few oases in Junggar basin, mainly distributed in the northern Tianshan Mountains. There are basically no oases in the eastern margin of the basin, because there are no tall mountains to provide water for the development of oases.
Qaidam Basin
Qaidam basin is a giant basin with the deepest subsidence in Qinghai-Tibet Plateau, which is slightly equilateral triangle. Located between Altun Mountain, Qilian Mountain and Kunlun Mountain in Qinghai Province, it is 800 kilometers long from east to west and 350 kilometers wide from north to south, covering an area of about 220,000 square kilometers. It consists of many small mountain basins. The basin is high in the west and low in the east, with an altitude of 2,500-3,000 meters, which is 2-3 times higher than that of the Tarim Basin, and is a plateau basin. From the edge of the basin to the center, there are Gobi, hills, plains and lakes in turn.
"Qaidam" means "Yanze" in Mongolian. 230 million years ago, it was a big lake. Later, the western part of the basin rose and the lake gradually narrowed, leaving more than 5,000 salt lakes. Chaerhan Salt Lake, located in the center of the basin, is the largest salt lake in China, with an area of about 1.600 square kilometers and a salt storage capacity of 25 billion tons, which can be eaten by people all over the country for 8,000 years. A large area of hard and deep salt cover is formed on the surface of salt lake, and the thickest part reaches 15 meters. There are 3 1 km highways running through the north and south of the basin and built on the salt cover of Chaerhan Salt Lake. Many houses here are also built with salt blocks. There are also colorful salt crystals in the basin, among which crystal salt blocks can be carved into various works of art. Qaidam is not only a world of salt, but also rich in oil, asbestos and various metal deposits, and was once known as the "cornucopia". Nowadays, this "cornucopia" that has been sleeping for thousands of years is being built into one of the important industrial bases in the northwest of China, and its eastern and southeastern parts have become newly reclaimed agricultural areas.
Sichuan Basin
The natural scenery of Sichuan Basin is quite different from the three great basin mentioned above. The rivers here are surging all the year round. The dense forests and green fields set off the purple soil, and the red and green set each other off, making this basin, which is known as the "land of abundance", particularly enchanting.
Sichuan Basin is a hilly basin with an area of about 200,000 square kilometers, which is not only complete in shape, but also a standard structural basin. Surrounded by Qionglai Mountain, Longmen Mountain, Daba Mountain, Wushan Mountain and Dalou Mountain, the altitude is1000 ~ 3000m. Rich in purple sand shale, it is called "purple basin" and "red basin". About 654.38+35 million years ago, Sichuan Basin was still an inland lake. Later, due to crustal movement, the surrounding area rose to a mountainous area, and Wushan on the eastern edge was low. The lake overflowed from Wushan, and the bottom of the lake gradually dried up and became a basin. Under the action of horizontal crustal movement, all the mountains in the basin are arranged in southwest-northeast direction, with the highest terrain in eastern Sichuan, and Huaying Mountain, the highest peak, is about 1800 meters above sea level, which is the highest point in the basin. The hills in the middle of the basin are gently undulating, accounting for almost half of the basin, forming a hilly basin.
Chengdu Plain, located in the west of the basin, is a fan-shaped alluvial plain formed by continuous crustal subsidence and long-term accumulation of sediment carried by rivers. Rivers and canals crisscross the plain, which is convenient for irrigation. This is the essence of Sichuan Basin. More than 2,200 years ago, the ancient working people in China built the famous Dujiangyan water conservancy project in Chengdu Plain and the upper reaches of Minjiang River for flood control and irrigation.
Dujiangyan is a levee built near guanxian in the center of Minjiang River, which divides Minjiang River into Neijiang River and Waijiang River. The weir tip at the front end of Dujiangyan resembles a fish mouth, which is called Du Jiang fish mouth. The outer river rolls down and flows into the Yangtze River. The water from Neijiang passes through the artificially cut headland and is introduced into Chengdu Plain through the channel. This water intake is called "Baojingkou", and the stone pile isolated from the shore after being cut is called "Staying Pile". In order to control irrigation water, a sand-flying weir was built between the inner and outer rivers in the lower reaches of Dujiangyan, so that all the water in Neijiang flows into the river when it is flat, and the excess water can be discharged into the outer river over the sand-flying weir when it is flooded. After the completion of this project, millions of acres of farmland were irrigated, which effectively promoted the agricultural production in Chengdu Plain. Working people also carved Shui Ge on the stone wall of the bottle mouth, observed the change of water level, and accumulated a lot of valuable experience in water conservancy projects.
Except alluvial soil in Chengdu Plain, the vast hilly areas in Sichuan Basin are covered with purple soil. This kind of soil is weathered from purple sand shale and contains mineral nutrients such as phosphorus and potassium needed by plants. This is one of the most fertile soils in southern China. However, due to loose soil, abundant precipitation and hilly terrain, soil erosion is easy to occur in places lacking vegetation protection. For a long time, people in Sichuan have built many terraces to conserve water and soil.
Sichuan basin has experienced a history from continental basin to sea basin, from sea basin to lake basin, and then from lake basin to continental basin, and rich minerals such as coal, iron, salt, natural gas and oil have been deposited. Coupled with the warm and humid climate and intensive fertile soil in the basin, the Sichuan Basin, known as the "Land of Abundance", is not only an important grain-producing area of rice, wheat and corn in China, but also rich in sugarcane. After the founding of New China, heavy industries such as steel, machine building, chemical industry and many light industries also developed rapidly. Today, Sichuan Basin is being built into an important modern industrial and agricultural production base in China.