VGP - Phong Nha – Kẻ Bàng National Park displays an impressive amount of evidence of history of the earth. It contains an extremely important source of facts relating to geologic, geomorphic and geo-chronological history of the region.
The karst formation founded in the Phong Nha – Kẻ Bàng National Park evolved since the Palaeozoic (some 400 million years ago), constituting it as the oldest major karst area in Asia. Subject to massive tectonic changes, the park’s karst landscape is extremely complex with many geomorphic features of considerable significance. Extending to the border with Laos, the vast area contains spectacular formations, including 65 km of caves and underground rivers.
Phong Nha is part of a larger dissected plateau, which also encompasses the Kẻ Bang and Hin Namno karsts. The limestone is not continuous and demonstrates complex inter-bedding with shales and sandstones. This, together with the capping of schists and apparent granites has led to a particularly distinctive topography.
The caves demonstrate discrete episodic sequences of events, leaving behind various levels of fossil passages, formerly buried and now uncovered palaeokarst (karst from previous, perhaps very ancient, periods of solution); evidence of major changes in the routes of underground rivers; changes in the solutional regime; deposition and later re-solution of giant speleothems and unusual features such as sub-aerial stromatolites.
The location and form of the caves suggests that they might owe much of their size and morphology to some as yet undetermined implications of the schists and granites which overlay the limestone.
On the surface, there is a striking series of landscapes, ranging from deeply dissected ranges and plateaux to an immense polje. There is evidence of at least one period of hydrothermal activity in the evolution of this ancient mature karst system. The plateau is probably one of the finest and most distinctive examples of a complex karst landform in Southeast Asia.
This sector has many 'fossil' caves at a high level, which occur when the groundwater and rivers move to a lower level. Only a very few have been visited to date. It is one of the most important eco-regions of the Indo-Pacific. A large number of faunal and floral species occurs in the park, including some endemic to the site.
Phong Nha – Kẻ Bàng area is noted for its cave and grotto systems as it is composed of 300 caves and grottos, divided into three main systems: Phong Nha Grottos, Vòm Caves, and Rục Mòn Caves.
The Phong Nha grotto system is 40 km long in total, rising from south of Kẻ Bang Limestone Mountain. The main entrances are Khe Ry and En Grottoes situated at a height of 300m above sea level. The grottoes of this tree-branch system run in the direction of northeast-southwest.
The system of Vòm caves is over 30km long, rising from Rục Cà Roòng Cave located at a height of 360m above sea level and ending with Vòm Cave. The system runs south and north. Rục Cà Roòng River sometimes hides in mountains, sometimes appears in narrow and deep valleys, and flows into the Chày River at the entrance of Vom Cave.
The system of Rục Mòn caves that lies in the district of Minh Hóa is also a large cave. However, the information about this system is not abundant because few surveys have been conducted in this area so far.
Next to the Phong Nha Grotto is Tiên Sơn Cave – also known as Dry Grotto or Upper Phong Nha, a famous beautiful cave in Phong Nha – Kẻ Bang area – where features spectacular stalactites and stalagmites shaped like several fairy-tales. In addition, the Thiên Dương Cave remains untouched, with a very splendid beauty, longer and larger than Phong Nha or Tiên Sơn Grottos.
Especially, Sơn Động Cave is one of the most newly-found caves in the national park discovered by British explorers in April 2009. It is regarded as the largest cave in the world. The biggest chamber of Sơn Động is over five kilometers long, 200 meters high and 150 meters wide.
Some 92% of the park is covered by tropical forest, 92.2% of which is primary forest. By far the largest vegetation type is tropical dense moist evergreen forest on limestone. Although this was severely damaged by fire during the war, it is recovering rapidly and is now in a healthy state. It has a high level of faunal diversity and there are many vascular plants.
Statistics show that the flora in Phong Nha – Kẻ Bàng belongs to 152 families, 511 branches, and 876 species, including 38 listed in Việt Nam’s Red Book, 25 in IUCN’s Red Book (International Union for Conservation of Nature and Natural Resources) and 13 endemic species.
A very important discovery in this national park is three rare and precious species – Sao la, Mang lớn and Mang Trường Sơn – were founded in this area. Especially, Sao la and Mang lớn are new species discovered in the world.
Of the 81 recorded reptile and amphibian species, 18 are listed in Việt Nam’s Red Book and 6 in the IUCN Red List of Threatened Animals. In addition, there are 259 butterfly species, 72 fish species including 4 endemic ones in Quảng Bình only and one first found in Việt Nam; 302 bird species including 15 species listed in Việt Nam’s Red Book and 19 in IUCN Red Book. Particularly, black-comb blue pheasants, white-tail blue pheasants and peacocks are the global-level endangered species. Phong Nha – Kẻ Bàng is considered a huge biological museum in Việt Nam.
With its vivid evidence of the Earth’s formation, geological, topographic and geomorphologic history, mysterious landscapes and rich bio-diversity, as well as its unique historical and cultural values, Phong Nha – Kẻ Bàng has been declared a world natural heritage by the United Nations Educational Scientific and Cultural Organization (UNESCO) at the 27th meeting in Paris in July 2003.
Phong Nha-Kẻ Bàng Park takes pride in the assessment of containing “7 best things” as a result of a National Science Conference held in Quảng Bình in April, 1997. They are:
1. The longest water cave
2. The highest and widest cave mouth
3. The widest and most beautiful sand & rock bank
4. The most beautiful underground lake
5. The most magnificent and miraculous stalactite
6. The nation’s longest underground river (around 13,969 m)
7. The nicest and widest dry cave
By Thùy Dung