The famous mountain system in the middle of inland Asia is one of the rainy mountains in the arid areas of the world. Within the territory of China, the latitude direction runs through the central part of Xinjiang Uygur Autonomous Region, starting from Hami County in the east, 96 10' east longitude, and reaching the northwest of Wuqia County in the west, 74 50' east longitude. The length from east to west is about 1760 km. North and south span five latitudes (40 31'~ 45 23' north latitude, with a width of 250 ~ 350 kilometers and an area of about 4 1 10,000 square kilometers. This mountain is located between Junggar and Tarim basin, with an altitude of more than 4000 meters. Tomur Peak, located in the western section, is the highest mountain in Tianshan Mountain, with an altitude of 7435.3 meters. The peak in the eastern section is Bogda Peak, with an altitude of 5445 meters.
Geological and Physical Geographical Division In geological history, Tianshan geosyncline was formed in Late Sinian. After the Caledonian movement, especially the Variscan movement, the geosyncline returned in an all-round way and folded and uplifted to form the ancient Tianshan Mountains. The main rocks that make up the mountains are Paleozoic metamorphic rocks, pyroclastic rocks and Variscan intrusive rocks. From Mesozoic to the end of Eogene, the ancient Tianshan Mountains were denuded and leveled into a quasi-plain. In the Late Tertiary, especially after Pliocene, the fault block uplift occurred in the quasi-plain, forming a multi-level mountain planation plane. After the alternation of glaciers and flowing water, it became the modern Tianshan Mountains. It is an important earthquake zone in China. From 1600 to 1979, there were more than 500 earthquakes of magnitude 4.6 or above in Xinjiang, of which more than 50% occurred in this area.
The mountain range consists of a series of roughly parallel northern Tianshan, middle Tianshan and southern Tianshan, and there are many wide valleys and basins between the mountains.
The process of modern landform in Tianshan Mountain from the top of the mountain to the bottom of the mountain is as follows: ① perennial snow and modern glacier area. Located at an altitude of 3800 ~ 4200 meters, it is a very high mountain belt covered with snow and ice. According to statistics, there are nearly 7,000 modern glaciers in Tianshan Mountain, covering an area of 1 1,000 square kilometers. ② Frost area. Located in the mountainous area above 2600 ~ 2700 meters above sea level, a large number of ancient glacial sediments have accumulated, forming various glacial erosion landforms-ancient ice bucket, ice trough valley, ice ridge and so on. Has been preserved. The negative temperature period lasts for half a year and only thaws in midsummer. ③ Running water erodes the accumulation zone. It is located at an altitude of1500 ~ 2,700 meters (or 2,800 meters), with dense river networks and developed valley terraces. (4) Drought and denudation in low mountain areas. It is located below the altitude of 1300 ~ 1500m, and the annual precipitation is 200 ~ 400mm. The southern slope is below the altitude of1700 ~ 2000m, and the annual precipitation is100 ~150mm. The external force is mainly dry erosion, especially on the south slope.
Climate and hydrology The climate in mountainous areas is obviously divided into cold and warm seasons in the middle of a year. How sunny it is in the cold season. The mountains, basins and valleys below 3000 meters are covered with deep snow, foggy and frosty. In warm season (summer), it is rainy and snowy above 3000 meters above sea level. The climate is cool below 3000 meters. The difference of humidity in different places is controlled by altitude.
In the mountainous area of Tianshan Mountain, especially in the west of Tianshan Mountain, obvious inversion stratification often occurs in winter. /kloc-reversed in October and disappeared in April of the following year. In June 5438+ 10, the stratification was the largest, reaching about 3000 meters.
The annual precipitation in Tianshan mountain area gradually decreases from west to east on the same hillside; The windward slope (north slope) in mountainous area is larger than the leeward slope (south slope); There are fewer basins or valleys in mountainous areas than in peripheral mountainous areas. Bayinbuluke, located in Tianshan Mountains, is 2,438 meters above sea level, with an annual precipitation of only 2,762 mm, which is less than that in mountainous areas at the same height. However, the terrain is wide and flat, meanders are developed, precipitation is concentrated in summer for half a year, lakes and swamps are dotted with beautiful water plants. It has become one of the famous grasslands in China, and it is the only place where swans live in Tianshan Mountain. Now it has been designated as a nature reserve in Xinjiang.
The average annual precipitation on the northern slope of Tianshan Mountain is more than 500 mm, which is a humid island in arid areas of China. Among them, the mountain forest belt in the west is the most, reaching 1 139.7 mm (recorded in 1970). The annual precipitation in Toksun near the sea level is the least, only 6.9 mm. The precipitation season varies greatly, with the maximum precipitation concentrated in May and June and the least in February.
The maximum precipitation zone in Tianshan Mountain moves up and down with the seasons. The maximum precipitation zone in winter is 1500 ~ 2000m above sea level, which starts to move upwards in early summer and rises to the extremely high mountain area with an altitude of 5000m in July and August. After that, they began to return. Winter 10 back to its original position. The rainstorm in mountainous area lasts for a short time, but its intensity is high. The distribution of snow is the same as that of precipitation.
Tianshan Mountain is the source of many rivers in Xinjiang, such as Yili River and Tarim River. There are more than 200 rivers in the mountainous runoff formation area with less than 200,000 square kilometers, with an annual total runoff of 43.6 billion cubic meters, accounting for 52% of the total runoff in Xinjiang. Water diversion irrigation covers oasis farmland in 57 cities and counties in Xinjiang. According to the catchment area above the mountain pass of each river, the annual average runoff depth is 271mm. The coefficient of variation of annual runoff is generally 0. 1 ~ 0.2, and the variation is relatively stable. The coefficient of variation of annual runoff is one of the smallest areas in China.