Explore the Caves

Yuanhai+ZHANG

The cave is a place full of mystery. Because of the infinite magic given by the creator, or the humans love for exploration, the cave has always been be humans curiosity. Now, let us follow the experts on karst geology to explore the mysterious world of karst caves.

The Secret of the Karst Cave

Karst caves are the underground world of Karst landforms, which is formed by the action of water migration, dissolution, erosion and gravitational collapse on soluble rock. Initially, the space for water transport was that of an original pore, which means it is very narrow, the flow is mainly laminar and the dissolution is very slow; when pores develop into holes, the flow is slightly faster; as the turbulence action occurs, the dissolution is enhanced, and a narrow net of holes is formed. Affected by geologic factors, water flow then decides on an optimal path and is enlarged to form the cave. Karst caves, ranging from short, single underground space to the hundred-meter-long underground channel network which is large enough to fit aircraft. They are the most amazing and mysterious places on Earth.

The Climate Change in the Cave

Karst cave is a damp, dark, quiet and independent underground world with relatively stable environment and constant temperature with no direct solar radiation or the impact of the skyshine.How do carst caves adjust their ownclimate? It turns out that the climate change of Karst cave is mainly realized by the movement of air and water in the cave. In general, the temperature of the entrance zone is largely affected by the external environment. The daily and yearly variation of its temperature is similar to that of the local surface temperature. The deeper into the hole, the smaller the temperature fluctuation to an extent that it is not affected by the outside world and remains stable on the local average temperature.

The flow of air can be felt in most caves. Some blow cool breeze in summerwhile some spray hot wind in winter.The air in some caves is periodically sucked in and blown out, forming breathing caves. The more entrances, the more frequent the exchange of air with the outside world and the greater the climate fluctuation is. If there is a sharp difference in yearly and daily temperatures in the location of the caves, there will occur air flow. In summer or midday. The air often flows to outwards while in winter or at night, the air flows mostly inwards.

How Old is a Cave?

How many years has it been since the cave was formed? This problem needs to be solved through terrain analysis. For example in high latitudes, because of the large area of glacier erosion caused by climate change since the Quaternary period, the ancient caverns may have gone long ago; in low latitudes, although some old caveshave been preserved for not being affected by glaciers, however, even those large tunnels are millions of years old and caves with tens of thousands of years of history may be buried in the depths of the underground, even if there is a cave space,it is likely to befilled with sediment.

We can rely on these filling sediments to determine the relative age and absolute age of karst caves through the ancient geomorphology analysis, using the paleomagnetism, carbon-14, thermoluminescence, luminescence, fission track method, cosmogenic dating methods. Recently, the researchers collected quartz in the sediments of the ancient underground river of the Golden Buddha Cave in Chongqing.The cave dates back to at least5.7 million years ago as measured by the cosmogenic method, which is the oldest cave in China with basic data , which has changed the general view in China that Karst cave formed in Quaternary. Besides, we can establish the process of regional geologic history evolution, especially the time line of various events if we can determine the age of the caves according to the information of various paleo-environment changes.

The Memory of the Stalagmites

The water drops from the top of the cave went through the fissures in the carbonate rock and stopped at the bottom of the hole. During the process, carbon dioxide is constantly effused, and the water is saturated to form calcium carbonate that is deposited at the bottom of the cave.Day after day, there slowly grow stalagmites.

Stalagmite has the unique growth characteristics similar to a cap, and its formation process contains the ancient geochemical characteristics. It a rare information source of the terrestrial environment in ancient times because of the wide distribution, large span of time, little interference from the outside, insensitivity to the outer environment and low cost in age-dating and sampling.By sampling from the growth axis along the stalagmite and measuring its age, the ancient climate of precipitation and temperature can be reconstructed.

The deposition rate of stalagmites is different under different conditions.The current research has found out that the growth rate of stalagmite ranges from 1mm per 1 millennium to more than 10mm per century; sometimes it does not even grow. Under the control ofclimate revolution, the rule of the growth and ungrowth of stalagmites is the key to exploring the mysteries of monsoon intensity, precipitation, temperature and the change of ecological environment.

Creatures in the Cave

Caves, in fact, is more than stones, it is also a home of many living creatures. Just as cities are divided into blocks, a cave can be divided into different areas. Near the mouth of the hole, the sun light is ample and changes in accordance with the seasons; this area is called the entrance of the mouth. A little deeper into the cave, the light is darkened; the area that is basically visibleis called the dyssophotic zone; there is no light farther down. Unable to see ones hands--the area is called the dark zone.

Plants in the Cave

In the the entrance of the mouth where the light is strong, there are green plants. However, due to the limited space and sunlight, the herbaceous plants take a dominant place while shrubs, vines and tall trees are less. Thedyssophotic zone is connected with the outside world through the hole, with small intensity of light and huge humidity is big.Seeds, mainly the seeds of plants resistant to damp and dark environment like Pilea cadierei, Pteris multifida Poir, moss, nostoc and Cyanobacteria are brought into the hole through the rain, wind, animals and so on. Because there is no light in the dark zone, plants cannot perform normal photosynthesis, there are no green plants but only fungi here. Some plants such as gesneriadcan only grow in caves because of their adaptation to the cave environment, and they cannot grow normally if they leave the caves.

Animals in the Cave

Originally, the cave animals were those that lived on the surface of the earth, which, for some reason, migrated to caves and adapted to the environment in the cave over a long period of time.

Snakes, mice, flying cats, sparrows and so on often go in and out through the entrance, they are cave animals that occasionally go into the cave, but which do not reproduce and live in the cave.

The dyssophotic zone where sunlight can not directly reach is the home to bats, swiftlets, spotted stoves horses, centipedes and other animals which like to live in caves. They can live in the dark environment of the cave and live outside the cave. They spend most of the time staying in the cave.

In the dark zone of the cave, which is the residence of the Astyanax jordani, jullid, woodlice and other animals which often live in caves(also called the troglosblos), the temperature and humidity rarely change throughout the year. The animals here have been fully adapted to the dark cave and have lost the ability to survive outside the cave after a long period of evolution.

In all the caves, the food chain of animals begins in the outer world.The animals occasionally live in caves, the animals fond of living in caves and the underground water bring the carcasses, mosquitoes and feces into caves, becoming the food source of the animals that often live in caves. Furthermore, there is a competition of the jungle in the depths of the cave.

Featured Karst Caves

There are many karst caves globally with new ones being found every year.

The longest cave in the world is the Mammoth Cave in the US with a length of 651784 meters. The world's top ten largest caves are mostly located in America, five of which in the United States and 2 of which in Mexico. China's longest karst cave is the Shuanghe Karst Cave in Guizhou, with a length of 200427 meters, ranking tenth in the world.

The deepest cave in the world is Georgia's Krubala Cave, which is measured 2197 meters deep. It is located in the western Caucasus region, where the shafts are particularly numerous. China's deepest group of shafts is located in the vicinity of Chongqing's Wujiang River, with a depth of thousands of meters.

Besides, there are 13 cavern halls that are more than 1 million cubic meters. The largest is Miao Hall in Guizhou , 10.57 million cubic meters; the one with the largest basal area is the Sarawak Hall in Malaysia, up to 160,000 square meters and the highest is the Ladder Hall in Chongqing, 365 meters high.

Karst caves have become an extremely important resource for tourism , with a variety of landscape and quiet environment. Incomplete statistics show that there are more than 1600 touring caves in the world, of which over 800 are in China. Many caves are an important part of the world's natural heritage, such as the Mammoth Cave in the United States and China's Furong cave. Exploring caves, not only can increase knowledge, but also raise the awareness of protecting the environment and the earth.