Characteristics of China’s four major basins
Four major basins: the Tarim Basin in the south of Xinjiang Uygur Autonomous Region, the Junggar Basin in the north, the Sichuan Basin and the Qaidam Basin in northwest Qinghai.
(1) Tarim Basin
It is the largest inland basin in China, located between the Tianshan Mountains and the Kunlun Mountains. The widest point from north to south is 520 kilometers, and the longest point from east to west is 1,400 kilometers. It covers an area of approximately 400,000 square kilometers.
The Tarim Basin is a large closed intermountain basin, geologically speaking, it is a stable massif surrounded by many deep and large faults. The base of the massif is ancient crystalline rock, with a Paleozoic and Proterozoic sedimentary cover about a kilometer thick on the base, and a thin Mesozoic and Cenozoic sedimentary layer above it. The Quaternary sediments cover a large area. The terrain of the basin is higher in the west and lower in the east, tilting slightly to the north. The elevation of the old Lop Nur lake is 780 meters, which is the lowest point in the basin. The Tarim River is located on the northern edge of the basin, and the water flows eastward.
(2) Junggar Basin
Northern Xinjiang. The basin is in the shape of an irregular triangle, with the terrain higher in the east and lower in the west. There is a vast desert in the middle of the basin, and the northwest receives slightly more precipitation due to the influence of ocean moist airflow. The basin has vast pastures, developed animal husbandry, and considerable scale in oasis and land reclamation agriculture.
The Junggar Basin is located between the Altai Mountains and the Tianshan Mountains, with the western Junggar Mountains to the west and the foothills of Beita Mountain to the east. It is 450 kilometers wide from north to south, 700 kilometers long from east to west, and covers an area of 180,000 square kilometers, with desert accounting for 30%. The terrain slopes to the west, with the north slightly higher than the south. The lake level of Ulungu Lake (Brento Sea) in the north is 479.1 meters, the lake level of Manas Lake in the middle is 270 meters, and the lake level of Lake Aibi in the southwest is 189 meters. It is the lowest point in the basin. There are several gaps on the west side of the basin, such as the Irtysh River Valley, the Emin River Valley and the Alashankou. The westerly airflow enters through the gap and brings precipitation to the basin and surrounding mountains.
(3) Qaidam Basin
It is one of the three major inland basins in China and is a closed huge intermountain fault basin. Located in the northwest of Qinghai Province. It is surrounded by the Kunlun Mountains, Qilian Mountains and Altun Mountains, covering an area of approximately 250,000 square kilometers. "Qaidam" is Mongolian, meaning "salt lake"
. The Qaidam Basin has a plateau continental climate, characterized by drought. The annual precipitation decreases from 200 mm in the southeast to 15 mm in the northwest, and the average annual relative humidity is 30% to 40%, with a minimum of less than 5%. The annual average temperature in the basin is below 5°C, and the temperature changes drastically. The absolute annual temperature difference can reach more than 60°C. The daily temperature difference is often around 30°C, and it can drop below 0°C at night in summer. The wind is strong, and the number of windy days above level 8 can reach 25 to 75 days a year. Strong winds of 40 meters/second can even occur in the west, and wind erosion is strong.
(4) The Sichuan Basin
is a famous red bed basin in China. It is the basin with the most typical shape, the southernmost latitude and the lowest altitude among all major basins in China. Located in the eastern part of Sichuan Province, on the upper reaches of the Yangtze River, it covers an area of more than 260,000 square kilometers, accounting for 46% of the area of Sichuan Province. The Sichuan Basin borders the Qinghai-Tibet Plateau and Hengduan Mountains to the west, the Qinling Mountains and the Loess Plateau to the north, the mountains of western Hunan and Hubei to the east, and the Yunnan-Guizhou Plateau to the south. There are many low mountains and middle mountains on the edge of the basin, and the mountains are steep. Most of the rivers originating from the mountains on the edge of the basin are "V" shaped valleys. The height difference between the ridges and valleys exceeds 500 to 1,000 meters. The surface is rugged, so there is a saying in history that "the road to Shu is difficult". , it is said that it is difficult to reach the blue sky.” Karst landforms such as stone forests, caves, underground rivers, and troughs can be seen in the limestone distribution area. Xingwen County on the southern edge of the basin is known as the "Stone Forest Cave Township." Famous mountains such as Wushan Twelve Peaks and Jinfo Mountain are also mainly developed from limestone. Mount Emei, which is composed of limestone, basalt, and granite, and Mount Qingcheng, which is composed of sandstone, mudstone, and conglomerate, are known as "Emei is beautiful in the world" and "Qingcheng is quiet in the world" and are famous tourist attractions in China.