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Dragon Hole in South China Sea

A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of limestone or coral reef. Blue holes typically contain tidally-influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages.


The well-known blue hole in China is Sansha Yongle Blue Hole, also called Dragon Hole, located in the Xisha islands, Sansha city. It is has been certified as the deepest blue hole in the world at 300.89 meters. The diameter of the sinkhole's top entrance measures about 130 meters; and the bottom measures 36 meters, according to Track Ocean, a private research organization whose research institute probed the sinkhole several times.


According to the research and analysis, Blue hole formed during past ice ages, when sea level was as much as 100–120 meters lower than at present. At those times, these formations were targets of the same erosion from rain and chemical weathering common in all limestone-rich terrains; this ended once they were submerged at the end of the ice age.

The Blue hole is roughly circular, steep-walled depression, and so named for the dramatic contrast between the dark blue, deep waters of its depths and the lighter blue of the shallows around it. The water circulation is poor, and it is commonly anoxic below a certain depth; this environment is unfavorable for most sea life, but nonetheless can support large numbers of bacteria. The deep blue color is caused by the high transparency of water and bright white carbonate sand. Blue light is the most enduring part of the spectrum; other parts of the spectrum—red, yellow, and finally green—are absorbed during their path through water, but blue light manages to reach the white sand and return upon reflection.


There exists a long legend about the Dragon Hole. According to the local fishermen, they said that the blue hole is the place that stands the golden cudgel, or it is the eye of the South Sea with treasure.

To protect the maritime environment in the South China Sea, Sansha city has banned fishing and tourism in and around the blue hole.



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Carrie is an experienced traveler herself who has traveled to many countries such as Indonesia, Malaysia, Singapore, South Korea, USA, etc. She thinks travel is one of the most important things in her life.


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