Son Doong Cave was formed in the limestone block of the Bac Son formation. On the walls and floor of this vast cave, many different types of fossils can be found, such as coral, sea urchins, mammals, and more. However, the most notable fossils discovered in the cave are an ancient coral species (Coralla) and a hoofed mammal fossil (Euungulata), which can be considered some of the most prominent paleontological relics in the karst caves of Vietnam. To this day, Son Doong Cave still holds many mysterious features that attract explorers and even Hollywood filmmakers to discover. Let’s explore with BestBooking Vietnam Travel to see what makes it so special, drawing the world’s attention.
Overview of Karst and Natural Heritage Related to Karst Landscapes in Vietnam
Son Doong Cave is one of the karst caves in Vietnam. According to Time Out magazine, Son Doong was discovered in 1990 and recognized by the Guinness World Records as the largest natural cave in the world, with a volume of approximately 38.5 million cubic meters. It was also recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO) as a World Natural Heritage site in 2003.
Karst is a weathering phenomenon typical of rocks that are capable of dissolving in natural water. Among these dissolving rocks, limestone is the most common, and therefore, the term “karst” is typically used to describe regions with widespread limestone around the world. From this, a series of related terms have arisen – karst landscape, karst cave, karst water, etc. Due to its wide distribution, karst often forms unique landscapes with high aesthetic value, as well as particular characteristics in terms of hydrology, soil types, and biodiversity. Karst processes are primarily understood as the dissolution of rocks that can dissolve in natural water, mainly carbonate rocks, which create different types of karst landscapes.
Son Doong Cave – The largest Karst Cave in the world with many impressive records
The largest karst cave in the world
The largest world record of Son Doong Cave was announced by the Royal Association of Caves of England in 2010. The main branch of Son Doong Cave is 6,781 meters long, with an average width of 50 – 80 meters and an average height of 80 – 100 meters. The widest part of the cave reaches 150 meters, and the highest part reaches 195 meters (measured at the foot of the Vietnam Wall), large enough to contain a 60-story building (each floor over 3 meters). This size is beyond imagination, surpassing the Deer Cave on Borneo Island in Malaysia, which previously held the record – the Deer Cave was only 1.6 km long (Limbert H. et al., 2012).
Accurately measuring the cross-sectional area of the cave chambers is often difficult because they are so vast. Meanwhile, one chamber of the Deer Cave in Sarawak (Malaysia) was accurately measured, with a width of 168 meters and a height of 125 meters (Waltham and Despain, 2012). This size is certainly larger than any part of Son Doong Cave. However, the part with the largest cross-section of the Deer Cave is less than 1 km long, while Son Doong Cave maintains its large dimensions for more than 3 km. Therefore, H. Limbert and his colleagues have confirmed that Son Doong is the largest karst cave in the world (Limbert H. et al., 2016).
Recent measurement results of Son Doong Cave’s dimensions using 3D laser scanning technology (with 150 scanning stations) and cross-checking laser rangefinder results provide the following:
- Length of Son Doong Cave (excluding branches and mud pools to the back entrance): 4,450 meters;
- The lowest point from the floor to the ceiling: 18 meters;
- The highest point from the floor to the ceiling: 203 meters;
- The highest point from below to above the collapse hole (doline): 304 meters;
- The narrowest point (wall): 18.8 meters;
- The widest point (wall): 147 meters;
- The widest point (wall to the next chamber): 200 meters;
- Total volume of the cave: 12,500,000 cubic meters (excluding the volume of the mud pool at the foot of the Vietnam Wall).
Thus, with these measurement results, Son Doong Cave has the largest volume in the world, surpassing the Miao Cave in South China (which has a volume of 10,570,000 cubic meters).
These accurate measurements further confirm the conclusion of the Royal Association of Caves of England in 2010 regarding Son Doong’s record as the largest cave in the world, which at that time was not based on any specific criteria.
Impressive Stalagmite Formations
Son Doong Cave is home to colossal stalagmite formations, including the Dog’s Paw stalagmite cluster, which reaches a height of 70 meters. Not only is it tall, but the Dog’s Paw stalagmite also creates a beautiful and unique stalactite group, serving as a symbol for the first chamber of Son Doong Cave, which has been captured in stunning photographic artworks.
As the largest cave in the world, Son Doong features many other stalagmite formations of extraordinary size. Dozens of stalagmite clusters and stalactite chandeliers within the cave can reach tens of meters in size. Besides the Dog’s Paw stalagmite cluster, there are other massive and magnificent stalagmite formations in Son Doong, each with its own striking and unique beauty.
Stalagmites are not only formed within the cave as typically observed, but they also develop beneath the sinkholes, where powerful water flows from heights of hundreds of meters along the walls of the “skylights.” In this environment, a new type of stalagmite has emerged, one that has yet to be classified in the standard categorization of stalactites. These stalagmites are typically large, with a rounded top and a surface often covered in lush green vegetation, as they still receive sunlight.
Rimstone systems are commonly found on the floors of karst caves, but in Son Doong Cave, visitors can encounter enormous rimstone systems, with compartments filled with sand during the dry season, creating “terraces” where the uppermost layer forms a wide sandbank large enough for expedition groups to set up camp overnight.
Near the sinkholes in Son Doong Cave, a unique form of karst called phytokarst is developing. This is a type of karst related to plant activity. The scientific term “phyta” refers to plants. In fact, the formations of phytokarst resemble bundles of sticks arranged in parallel. At first glance, one might think this shape is due to the structure of the limestone. However, upon closer inspection, it is clear that the limestone here, before undergoing transformation, has a more solid structure, relatively uniform, and includes travertine blocks.
Son Doong Cave is home to a rich variety of cave pearls. They are found in many places, diverse in shape and color. Some have a rough surface, others are in the process of forming crystalline layers, while some are polished, showing strange and rare colors. With the naked eye, one can see round, smooth cave pearls resembling billiard balls, with spots of color like those of quail eggs, revealing the marvels of nature in this place. Mr. Howard Limbert, who has visited many caves around the world, has said that he has never seen cave pearls as numerous and large as those in Son Doong. Some of the larger pearls can weigh several kilograms.
Next to the large and small cave pearls scattered across the cave floor, in some places, a stalagmite tree grows with a rich ecosystem. In fact, this is a form of flowstone developing on the surface of a newly-formed limestone mound.
Along with the large stalagmite blocks, some reaching tens of meters in size, creating a breathtaking beauty for Son Doong Cave, there are also countless small but extremely enchanting formations due to their delicate and incredibly unique beauty, some even of a type not found anywhere else.
However, the most miraculous of the mini-stalagmite formations in Son Doong Cave are the stalagmite pools that have developed in areas with beautifully outlined rimstone pools with wide rims sloping downward. At the contact point of the northern branch of the cave with the Giant Sinkhole, near where the phytokarst landscape is developing, in addition to the usual flowstone formations, there is a very special type of stalagmite resembling a rocky forest with sharp peaks, hard and rigid, aligned with the flow direction during the rainy season. It is believed that their formation is related to the flowing water saturated with Ca(HCO3)2, but the mechanism behind the formation of these “directional rock mats,” tentatively called “washing stalagmites,” remains a mystery to science.
Ancient Fossilized Remains in the World’s Largest Cave
Tetracoralla Fossils
In the area near the first sinkhole, the “Dinosaur” sinkhole, along a passage leading to an underground river, numerous fossils of Tetracoralla (four-branch corals) can be seen on the walls, ceiling, and floor of the cave. These fossils belong to a type of solitary horn-shaped coral, with a diameter of about 3 cm and a length of up to 10 cm. Although the conservation regulations of Phong Nha-Ke Bang National Park prohibit the removal of samples from the cave walls, the fossils of Tetracoralla here are clearly visible on the rock surfaces, almost as if they have been polished, allowing them to be studied through photographs. According to Dr. Nguyen Duc Khoa, these corals belong to the Dibunophyllidae family and date back to the Carboniferous period. What is particularly remarkable is their abundance, representing part of the marine life in the Carboniferous period, about 300 million years ago.
In addition to the dominant four-branch coral fossils, other fossilized species such as Syringoporida (from the subclass Tabulata) and marine lilies (Crinoidea) can also be found in this ancient marine fossil deposit. Based on the analysis of foraminifera fossils extracted from the limestone containing the aforementioned marine fossils, several species of foraminifera, including Ozawainella angulate, Ozawainella leei, Ozawainella sp., Pseudostaffella yanbianensis, and Pseudostaffella sp., were identified with a Moscovian age, late Carboniferous (C2m). To date, this is the most significant and beautiful fossilized coral deposit ever discovered in the caves of Vietnam.
Fossilized Hoofed Mammal
At the far end of Son Doong Cave, after passing through the Vietnam Wall, there is a small travertine mound. This mound is located about 300 meters from the cave’s back entrance. On top of this fairly flat mound, there is a unique fossilized mammal skeleton. The bones are almost completely intact and arranged in a natural order, although the skull is missing. All of the bones have been calcified and are firmly embedded in the travertine floor. Scattered between the bones and on the surface of the mound are countless spherical cave pearls.
Vu The Long identified these fossils as belonging to the group of hoofed mammals (Euungulata), such as deer, antelope, or cattle. However, the fossils are relatively young in age. The skeleton was fortunate enough to be submerged in limestone-rich water and was calcified during the evaporation process. The animal likely represents a member of the contemporary fauna, which may have fallen into the cave due to some reason, becoming trapped and unable to escape because of an injury or the steep incline. Without food, it struggled to climb this small “hill” and eventually died there. This fossil is the largest and most well-preserved mammal skeleton found in the cave.
The Pristine Forest Inside Son Doong Cave
Son Doong Cave is the first and only cave in the world to house a pristine forest. This fact has been confirmed by explorers from the world-renowned National Geographic, who recognized it as one of the most unique caves on the planet. About 500,000 years ago, two sinkholes in the cave were formed, allowing sunlight to penetrate and creating an environment conducive to plant growth. This process led to the development of two pristine forests in Sinkhole 1 and Sinkhole 2.
Inside Sinkhole 1 is the “Dinosaur Observation Area” , characterized by a steep terrain with a cave floor mainly made of rock, with very little soil. Additionally, the narrow opening of the sinkhole limits the amount of sunlight (essential for photosynthesis) that enters, so only small shrubbery, such as ferns, moss, and algae, have been able to grow in this area.
Meanwhile, inside Sinkhole 2 lies the “Garden of Eden” , a vast pristine forest with towering trees over 40 meters high. Walking through this forest, you may feel as though you’re in a typical forest, but in reality, this forest is located more than 200 meters beneath the limestone mountain ranges and deep within the heart of Sơn Đoòng Cave.
Therefore, besides having many stalactites with strange and giant shapes, Son Doong Cave also has a pristine forest growing right inside the cave, called the Garden of Eden.
Newly discovered animal species
As of now, biologists have discovered more than 7 new species in Son Doong Cave, including some species of fish, lice, millipedes, spiders, scorpions… with the common characteristic of having no eyes and transparent bodies. These species have been recognized as new species by German and Vietnamese biologists.
The underground river inside Son Doong Cave
Son Doong Cave possesses a large underground river system, formed by the confluence of two rivers (the Rao Thuong and the river from Khe Ry Cave with water flowing from the Laos border) discovered in 2009. The underground river in Son Doong has made the environment and ecosystem inside the cave more unique and fascinating. The stream flows through many waterfalls inside, creating layers of mist and floating clouds of water vapor in the vast cave ceiling.
Son Doong Cave is a famous tourist destination in Quang Binh, located in Phong Nha – Ke Bang National Park. With its diverse ecosystem and natural wonders, Son Doong Cave deserves to be one of the top places many visitors want to visit when traveling to Quang Binh. Contact BestBooking Vietnam Travel now for advice on the best tour itinerary!
