How is the natural landscape of Jiuzhaigou formed?

Reasons for the formation of various natural landscapes in Jiuzhaigou;

1. Causes of water color: The lakes in Jiuzhaigou are colorful, which is mainly caused by the scattering, reflection and absorption of solar light by the lakes.

Reason: In the monochromatic spectrum of red, orange, yellow, green, cyan, blue and purple, the wavelength gradually becomes shorter from red to purple. Because there are very few suspended matter, organic matter and plankton in Jiuzhaigou Lake, the transparency and cleanliness of the lake are extremely high, and the Rayleigh scattering effect is more prominent. According to Rayleigh scattering effect, the scattering of short-wave light in lake water is much greater than that of long-wave light.

Therefore, the lake in Jiuzhaigou is bright blue-green. The common Ca2+, Mg2+ and HCO3- plasmas in lake water can also enhance the short-wave light scattering. At the same time, due to the high transparency of the lake, the gray-white travertine and yellow-green algae at the bottom of the lake selectively absorb and reflect the transmitted light, which also increases the level and change of the lake color.

In addition, the lakes in Jiuzhaigou are located in deep canyons, and the terrain fluctuates greatly. At the same time or at different times in different areas, the incident angle and amount of sunlight, the reflection of light on the lake and the transparency of the lake have all changed greatly, which also makes the color of the lake more colorful.

2. Causes of waterfalls: faults and biological karstification; Differential erosion and biological karstification; Gravity accumulation and biological karst such as collapse, landslide and debris flow.

Reason: The main waterfalls in Jiuzhaigou are Pearl Beach Waterfall, Nuorilang Waterfall, Shuzheng Waterfall, Panda Waterfall, Huohuahai Waterfall and Jianzhuhai Waterfall, which have the beauty of sound, color and shape. There are three main reasons:

First, faults and biological karst. Due to the influence of neotectonic faults, the riverbed of Jiuzhaigou is stepped in the longitudinal direction, and these topographic steps constitute the geomorphological basis of the waterfall. Due to the "bubble effect" and "thin water effect" of travertine deposition, travertine is easy to deposit on the terrain steps, which is helpful to the formation of waterfall scarps, such as Nuorilang Waterfall.

Second, differential erosion and biological karst. Because some rock formations are hard and soft, and the rock formations with strong corrosion resistance often protrude from the river bed, small water droplets are first formed at the protrusions of hard rock formations, and water-loving algae are first planted in these places, so travertine is first deposited in these places with relatively high flow velocity and shallow water flow.

Because the Quaternary sedimentary weir valley formed convex dikes, the velocity of flowing water suddenly increased when it overflowed on its surface, which was beneficial to the escape of CO2 and accelerated the deposition of travertine. As time goes on, travertine accumulates layer by layer. Because the growth rate of travertine in the upper part of its front edge is faster than that in the lower part, the lotus-like block forming travertine in the upper part gradually grows forward, and when the travertine block at the top extends down to the foot of the slope, it forms an upright waterfall surface, such as Pearl Beach Waterfall.

The third type is: gravity accumulation and collapse, landslide, debris flow and other biological karst. Waterfalls, such as Shuzheng Waterfall, are formed by overlapping biogenic travertine on the basis of loose deposits of collapse, landslide and debris flow.

3. The formation of Haizi: Haizi is another name for Jiuzhaigou. There are many lakes in Jiuzhaigou with complicated causes. The first condition for its development is to form a basin for collecting water and storing water, that is, a lake basin, and the second condition is to have water to fill the lake basin.

Reason: Jiuzhaigou lakes are mostly dammed lakes, and a few are glacial lakes, such as Yuanhaizi and Lvhaizi in the upper reaches of Changhai, and Longhai in kurama. The damming materials of these dammed lakes mainly come from glacier accumulation, biogenic travertine and gravity. These weirs blocked the valley and formed the lake basin of Jiuzhaigou. It can be roughly divided into four types.

First, on the basis of Quaternary ancient glacier erosion, lateral moraine and final moraine, the accumulation of gravity deposits such as collapse and landslide has been formed, such as Changhai, Wucaichi and Shangjihai. Second, it is formed by biogenic travertine and gravity deposits such as collapse, landslide and debris flow, such as Swan Sea, Arrow Bamboo Sea and Panda Sea.

Third, it is formed by biological travertine weirs, such as trees in the sea; The fourth is formed by gravity accumulation such as collapse, landslide and debris flow, such as the sea in the next season. The water filling of Jiuzhaigou Lake basin comes from atmospheric precipitation, but the recharge forms of different lakes are not exactly the same, mainly including rainfall, surface runoff, snowmelt water and groundwater.

The main ways of lake water discharge are evaporation, downstream runoff and underground leakage. The recharge and discharge of groundwater are mainly carried out through underground karst fractures, karst passages and catchment structures composed of faults and synclines. Faults, folds and topography control the recharge and discharge of lakes and the development direction of lakes.

4. Geological evolution history: crustal movement.

Reason: About 230 million years ago, Jiuzhaigou was still a piece of Wang Yang. After Indosinian and Yanshan movements, Jiuzhaigou formed a large number of folds and faults, and the whole scenic spot rose to land. Later Himalayan movement and neotectonic movement once again had an important impact on Jiuzhaigou stratum, causing it to rise again and fold and fracture, thus controlling the karst pattern of Jiuzhaigou.

In the Quaternary, the global climate became cold. Jiuzhaigou has experienced three ice ages, and glaciers are widely distributed, all of which are distributed over 2900 meters in the main ditch. The bottom moraine and the final moraine ridge formed by glaciation form a micro-geomorphological framework in the valley, which constitutes the embryonic form of Haizi in Jiuzhaigou. The last moraine ridge formed by the melting of glaciers cut off the flowing water in Zechawa gully, forming the largest lake in Jiuzhaigou-Changhai, which created the basic pattern of Jiuzhaigou water landscape.

Since Holocene, the crustal movement has tended to be stable, the climate has developed in the direction of warm and wet, and the snow line has retreated to more than 5000 meters. The underlying zone is dominated by geological processes such as karst, gravity collapse and debris flow, which has created and continued the unique layered lake waterfall landscape in Jiuzhaigou.

5. Karst landform: Jiuzhaigou has favorable conditions for karst landform development: rock composition, geological tectonic movement, climate precipitation and biological action.

Reason: The perennial temperature in Jiuzhaigou is lower than that in the south, and the surface erosion landscape is not prominent. Except for some gullies and stone buds on the upstream surface, the erosion is mainly carried out underground. On the contrary, the most striking thing is that there are a lot of travertine deposits on the surface, forming travertine veins, travertine pools, travertine beaches, travertine waterfalls and so on.

The strong evaporation in Jiuzhaigou, the decrease of pressure after groundwater overflow, the increase of water velocity in steep terrain and the absorption of carbon dioxide by aquatic plants are all beneficial to the deposition of travertine. This "reverse" karst landscape has become a masterpiece of nature.

The rocks in Jiuzhaigou are almost entirely composed of limestone, which is several thousand meters thick. Under the repeated action of geological tectonic movement, the grid-like fault system is very developed, and the differential uplift of the plateau edge forms a huge topographic contrast, which is beneficial to the circular movement of karst water. The climate in the basin is humid, the precipitation is abundant, the forest is dense, and the carbon dioxide content in the soil is high, which reduces the PH value of groundwater and greatly enhances the erosion ability of water to rocks. Biological action also accelerated the deposition of travertine;

6. Unique water circulation system: carbonate rocks and NW-trending structures widely distributed in Jiuzhaigou are the basis of water circulation, and the "three-water" circulation of atmospheric precipitation, surface water and groundwater constitutes the main body of Jiuzhaigou water circulation, and underground karst passages play an important role in the recharge and discharge of lake water.

Reason: Changhai is the largest sea in Jiuzhaigou, but there is no water outlet. Chawagou below Changhai is a dry valley with only a few seasonal lakes. Except for a small part of the water in Changhai, which is replenished to Caichi through the seepage of the natural dam in front of Haizi, more water is discharged to Rizegou Lake through the underground karst tunnel in the northwest.

The huge storage capacity of the Changhai Sea and its supply to Rizegou Haizi have played a role in regulating the reservoir, so that Rizegou Haizi will not dry up even in dry years and has a relatively stable supply.

The recharge of surface water and groundwater in Jiuzhaigou mainly comes from atmospheric precipitation, and the profit and loss of water basically depends on the change and temporal and spatial distribution of precipitation, which leads to great changes in the water level of lakes directly replenished by precipitation in the upstream, and the scenery changes at any time (in the upper and lower seasons), while the water level of lakes replenished by groundwater such as Wuhuahai is relatively stable.

Extended data:

The karst landforms in China are widely distributed and cover a large area. It is mainly distributed in the exposed area of carbonate rocks, covering an area of about 9 1 ~ 1.3 million square kilometers. Among them, Guangxi, Guizhou and eastern Yunnan have the largest areas and are one of the largest karst areas in the world. Tibet and some northern areas are also distributed. ?

In the world, the only karst landscape similar to Jiuzhaigou is Prithvi National Park. The landscape scale and biodiversity of Jiuzhaigou far exceed that of Cai National Park in Prithvi.

About 400 million years ago, it was a shallow sea with a large number of paleontologists. After hundreds of millions of years of geological movement, the sea disappeared and the Qinghai-Tibet Plateau appeared.

Later, glacial activities eroded the flat plateau, and peaks appeared, carving out deep and wide U-shaped valleys. The valley of Jiuzhaigou was formed at that time. The earthquake brought landslides, landslides and mudslides, and waterfalls gradually appeared. Nuorilang Waterfall was formed by mountain collapse.

The collapsed stones and mud blocked the river, and the accumulated water became a lake, and a dammed lake appeared. Wuhua Lake, one of the most beautiful classics in the ditch, originated from silt blocking the river.

"Jiuzhai returns without looking at the water" is a true interpretation of Jiuzhaigou scenery. There are 108 Haizi in springs, waterfalls, rivers and beaches, which constitute a colorful jade basin in Yaochi. The six landscapes of Changhai, Jianyan, Nuorilang, Shuzheng, Zharu and Black Sea are distributed in a "Y" shape.

Cuihai, Waterfalls, Colorful Forests, Xuefeng, Tibetan Love and Lan Bing are called "Six Wonders". The magical Jiuzhai village is known as "fairy tale world" and "king of waterscape".

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