Xiandu cave

Xiandu cave

Xiandu cave is located on the Bank of Xiandu River, Wanlong Township, Qijiang County, 180 kilometers away from Chongqing city. The cave was formed 100000 years ago and is the largest cave developed in the upper reaches of the Yangtze River. The cave is divided into three layers, with a depth of more than 12000 meters. More than 3000 meters have been developed. There are many kinds of stalactites, stalagmites, stone flowers and stone vines in the cave.

geographical environment

It is located in Xiandu River, Wanlong Township, Qijiang County, 180 kilometers away from Chongqing city. The cave was formed 100000 years ago and is the largest cave developed in the upper reaches of the Yangtze River. The cave is divided into three layers, with a depth of more than 12000 meters, and more than 3000 meters have been developed. There are many kinds of stalagmites, stalagmites, stone flowers and stone vines in the cave. Under the illumination of more than 2000 colored lights, the scene in the cave is more magnificent and fascinating.

natural resources

Peculiar landscape

There are various kinds of peculiar and spectacular caves, such as Qixingyan in Guilin, ludiyan, Qixingyan in Zhaoqing, etc. In the cave, there are various kinds of stalagmites and stalagmites, which are formed from calcium carbonate which is decomposed and then deposited. Natural river water or well water often contains impurities such as calcium bicarbonate, magnesium bicarbonate, calcium sulfate and magnesium sulfate. If the content is large, this kind of water is called hard water. Hard water is not suitable for industrial use, because it will decompose when heated in the boiler, resulting in poor heat conduction, waste of fuel and even accidents. Hard water is not suitable for drinking, such as long-term drinking, will suffer from digestive system and urinary system diseases. Washing clothes with hard water has poor washing effect. Karst refers to the landform formed by dissolution of soluble rocks, especially carbonate rocks (such as limestone, gypsum, etc.) by flowing water containing carbon dioxide and sometimes sedimentation. They are often in peculiar shapes, including caves, stone buds, stone ditches, stone forests, karst caves, underground rivers and cliffs. In this kind of landform area, there are often many peaks. There are such landforms in Guangxi, Yunnan and Guizhou of China. This is how the famous mountains and rivers in Guilin present their unique peaks and caves. The old name is karst, which originated from a place name in the former Yugoslavia. Surface water plays an important role in the erosion of sediments or rocks in the process of movement, including not only the transport of debris under hydrodynamic effect, but also the chemical dissolution of water on rocks or sediments, and the erosion of debris in the process of transport. Karst landform is the result of groundwater erosion on carbonate rocks. Under the action of current, it forms steep coast, curved gully, high ice erosion suspended Valley and Grand Canyon. "Dropping water wears away stone" is also a reflection of the chemical erosion of water. The formation of karst cave is the result of long-term dissolution of groundwater in limestone area. The main component of limestone is calcium carbonate (CaCO3). In the presence of water and carbon dioxide, the chemical reaction occurs to produce calcium bicarbonate, which is soluble in water, so there are cavities formed and gradually expanded. This phenomenon is most typical on the Karst Plateau along the Adriatic coast of Yugoslavia, so this kind of terrain in limestone area is generally called karst terrain.

Various classifications

1. The surface water dissolves along the joint surface or fissure surface of limestone to form a karst ditch (or trough), and the limestone distributed in layers is divided into columns or stalagmites by the karst ditch

2. The surface water seeps and dissolves downward along the limestone fracture, and forms a sinkhole when the depth is more than 100m.

3. The groundwater from the sinkhole flows laterally to the aquifer and forms a karst cave.

4. With the formation of underground caves, the surface collapses. The large depth and small area of collapse are called collapse funnel, while the small depth and large area are called collapse pond.

5. The dissolution and collapse of groundwater have been combined for a long time to form the slope Valley and Tianshengqiao.

6. As the surface rises, the original caves and underground rivers are lifted out of the surface to form dry valleys and stone forests, and the dissolution of groundwater continues under the old caves and underground rivers.

The stone forest in Lunan, Yunnan, is the product of the first stage mentioned above (dissolving ditch stage). The natural scenery here is particularly beautiful because of the moving legend of Ashima girl. The Xiangbi mountain in Guilin is formed by the original underground river course. This kind of cave, commonly known as "fairy mirror" or "fairy mirror", is often seen in Guangxi. The largest karst cave in the world is Mammoth Cave in the Appalachian Mountains of North America, which is located in Kentucky. The depth of the cave is 64km, and the total length of all bifurcated caves is 250km. The wide part of the cave is like a square, the narrow part is like a corridor, and the high part is 30m high. The whole cave is tortuous in plane and can be divided into three layers vertically. In rainy season, there is running water in the whole cave, which becomes an underground river. At the slope break, the river falls and forms a waterfall. In dry season, there is water in some areas, which becomes an underground lake. There may be a pool with deep water, which can be called bottomless pool. The longest known cave in China is Tenglong cave in Lichuan County, Hubei Province, about 40 km long, and the deepest is Wujia cave in Shuicheng, Guizhou Province. It's 430 meters deep. China is a country with many caves, especially the caves in Guangxi, such as Qixingyan and ludiyan in Guilin. The Yunshui cave in Shangfangshan, near Zhoukoudian in the southwest suburb of Beijing, is 612m deep. Seven "halls" are connected by a narrow and long "corridor". At the end of the cave is a huge stalagmite, which is famous as eighteen Arhats. Behind the stalagmite is a deep and inaccessible cave with a certain scale. Although the dragon bone cave in Zhoukoudian is not big, it is the habitat of our ancestors.

Tourism information

The traffic of Xiandu cave is convenient. Take bus no.326 at Nanping bus station to Shihao, then transfer to medium bus.

Cause of formation

Have you ever visited a cave?

There are many karst caves in the Karst Plateau of Yugoslavia and vast areas of southern China, such as Zhanggong cave in Yixing, Yaolin fairyland in Hangzhou, reed flute rock and Qixing rock in Guilin They are all tourist attractions. There are many kinds of stalactites, stalagmites and pillars in the cave. The spacious and tall caves and tortuous passages are like underground Dragon Palace, which makes people linger and forget to return.

So, how did the cave form?

In the past, people thought that karst cave was the result of groundwater dissolution and precipitation. Karst caves are formed by carbonate limestone, very hard, but long-term immersed in groundwater and dissolved, especially when the water contains carbon dioxide, the dissolution rate of rock is faster. So year after year, in the hard rock will be dissolved out of a cave. When the dissolved carbonate groundwater drips into the cave again, due to the decrease of temperature and pressure in the environment, the carbon dioxide in the water overflows again, so the solubility of water to limestone is reduced. As a result, part of the carbonate dissolved in the water is precipitated due to supersaturation, and the stalactites, stalagmites and pillars with different shapes are formed.

But in recent years, this traditional view has been questioned by Chinese cave scientists. After five years of investigation and study, they found that there was a very close relationship between algal organisms and the formation of karst caves, so they put forward the "biological construction theory", that is, a new theory of karst cave formation. According to this theory, algae are the earliest and still widely distributed primitive plants on the earth. Although they are low-grade, they have the same ability of photosynthesis and phototaxis as other plants. In the process of growth and development, they can secrete calcium, collect and bond fine carbonate particles, and generally live in clusters. Generation after generation of algae grow together, resulting in the formation of many marine reefs. Almost all stalactites in the cave bend upward to the light, which is consistent with the phototaxis of algae; there are concentric circles like tree rings in stalactites and stalagmites, which is the result of algae growing, secreting, collecting and bonding carbonate particles year by year. In addition, in the rocks of some caves, scientists have found layered fossil structures similar to ancient algae; in the surface of some caves, they have found a variety of algae that are still growing. Therefore, according to the theory of biological construction, although the formation of cave space is related to the dissolution of water, the formation of various stalactites, stalagmites and pillars in the cave should be mainly formed by algae gradually over a long period of time, and then through the process of fossilization, it finally presents today's appearance.

Legend

Karst caves have distinct characteristics of northern China.

The cave body is divided into upper, middle and lower layers. At present, the middle and upper layers of the cave have been developed, and other parts are being developed in succession. At present, the developed part here is composed of six scenic spots, which have four types and more than 20 forms of stalactites. The huge stone flower wall and dew drop stone are rare in China, which can be called the most in Northeast China. The DIHE river is clear to the bottom. It is said that washing hands and faces in the "shengshuixian River" will bring good luck to visitors. There are also "Tianfu stone forest", "immortal waterfall", "Yushu Qionghua", "Xianshan pagoda", "camel peak" and many other landscapes, which make visitors daydream. The air in the cave is smooth, and the constant temperature is 100C all the year round. It is cool and pleasant all the year round. It can be used as a choice for people to travel all the year round. The Guanma cave has been proved by experts to have a development area of more than 3800 square meters and a total length of 490 meters. It is composed of five halls and a water hall. Each hall is connected by a corridor. The largest hall is about 600 square meters, with a height of more than 30 meters. Guanma cave was about 100 million years ago

Chinese PinYin : Xian Du Rong Dong