Hang Son Doong: The largest natural cave on Earth with a hidden world beneath
Caves always ignite a sense of mystery among us, isn’t it? Our curiosity increases in leaps and bounds when we hear of one which has a volume of 38.5-million cubic metres. Yes, that’s the volume of the Hang Son Doong Cave located in Phong Nha - Ke Bang National Park, Quang Binch Province, Vietnam. Experts deem it as the world’s largest natural cave which spans through 9 kilometres. This case was first discovered in 1990 by Ho Khanh, a resident of Phong Nha. In 2009, after a formal survey and measuring of Hang Son Doong by the British-Vietnam Cave Expedition Team, it was declared the largest cave in the world.
But, what apart from its sheer volume makes this cave so unique? Well, it has a special underground world that is hidden from everyone. The Hang Son Doong cave is lined with delicate and huge, long thin pieces of rock on the ceiling. You’d be surprised to know that even today, ancient rainforests are thriving within the cave. Owing this this, the cave has its own unique weather and ecosystem. It also has a mystical underground river whose length is yet to be discovered. Interestingly, the name, Hang Sơn Đoòng, when translated from Vietnamese, means 'cave of the mountain river. According to Ginger Zee of ABC News, the visuals in Son Doong looks similar to that in the Avatar film. Interesting, right? Here’s a peek into the cave’s fascinating ecosystem.
Underground river
First things first. The river flowing into Son Doong is known as Rao Thuong. The water is supplied by many small streams in the surrounding jungles as well as from other caves. Abundant water supply makes Rao Thuong into a pretty big stream. It has small waterfalls along the way which create a loud rumbling sound. Sometimes, the cave is filled with mist too. Also, there are emergency bridges for use during the times when water levels rise.
Fossil passage
This cave passage, carved by the underground river, is filled with fossils. Its walls and ceilings have coral fossils, more than 300 million years old. The type of fossils founds here is that of four-branched coral (Tetra Coral fossil), which has gone completely extinct now. The largest among all of them is the one with a length of 10 cm. To add to the fantasy element of the cave, there is an underground pool too. Its temperature hovers around 16 to 17 degrees Celsius.
Cave pearls
If you are thinking that these the pearls that you get to buy in jewellery shops, you are wrong. The ones inside the world’s largest natural cave that we are talking about are ordinary calcium carbonate deposits. They look truly gorgeous when water streams through them. These cave pearls will lose their colour when left in sunlight. The biggest one found in Son Doong cave is the size of a baseball.
The Great Wall of Vietnam
After five days of exploration in 2009, the expedition team was forced to halt and take their way back. Why? A 90m high flowstone that blocked the pathway. This was named as the Great Wall of Vietnam. At that time, no one knew what lies beyond this wall, there was a glimpse of slim daylight. The team came back a year later in March 2010 when they climbed the wall using drills, anchors and specialised climbing techniques. At the end of this two-day expedition, the team reached the top where they saw light at a distance.