Cave systems in the area of Phong Nha-Ke Bang National Park is formed by the tectonic happens inside Ke Bang limestone mountain range more than 400 ago

Cave systems in the area of Phong Nha-Ke Bang National Park is formed by the tectonic happens inside Ke Bang limestone mountain range more than 400 million years ago during the Paleozoic. Experiencing the critical period of tectonic movements and the phases faulting, folding distribution platform and has consistently generated the same message mountains advanced motion and the motion sedimentary basin subsidence, play as the cause of all causes to create diversity of geology, topography – geomorphology, hydrology networks and the diversity and excitement of travel to the cave formations of limestone Phong.
400 million years to the Paleozoic era. Experiencing the critical period of tectonic movements and the phases faulting, folding distribution platform and has consistently generated the same message mountains advanced motion and the motion sedimentary basin subsidence, play as the cause of all causes to create diversity of geology, topography – geomorphology, hydrology networks and the diversity and excitement of travel to the cave formations of limestone Phong Nha Ke Bang evolved from Devon to Carbon – Trecmi.

Area Phong Nha-Ke Bang is currently aggregated results of the five major stages of development in the history of the Earth’s crust development in the region:

Late Ordovician Period – Siluri first phase (450 million years)
Devonian period between late (about 340 million years)
Phase Century Coal – Permian (300 million years)
Phase Orogen
Dai Tan Sinh period (250-65 million years ago)

Historical geological and geomorphological studies

For the first time, 20 teams of Geology, an agency under the Vietnam General Department of Geology has completed mapping the geological map at 1 / 500,000 North Vietnam in 1965 with the help of experts the Soviet Union, in which areas of Quang Binh province are classified structure object CTS. This is the first time the geological features such as stratigraphy, magmatism and structural – tectonics of this area was the Vietnam-Soviet scientists describe a systematic and detailed manner. After surveying and mapping, the Geological Survey of Vietnam (now the Department of Geology and Minerals of Vietnam) has continued to carry out geological mapping in medium and large ratio for defining the geological structure and determine the mineral potential in the territory and has completed geological mapping 1 / 200,000 sheet Mahaxay District – Dong Hoi accompanying notes to “geology and mineral sheet Mahaxay District – Dong Hoi”, this is the additional new research results on mineral stratigraphy and in the region. In 2001, geological mapping 1 / 50,000 map sheet accompanying explanatory report “Geology and mineral resources map sheet” was completed and brought a lot of new research results on paleontology and stratigraphy of Mesozoic phosphate minerals and building materials of the region. In addition, the scientists have also done many works published important studies on boundary Frasni – Famennian (Upper Devonian).

Natural features

Phong Nha-Ke Bang has a complex geological structure, the historical development of the Earth’s crust from Ordovicia period (464 Ma). This has created three types of terrain and landforms. One of them is the creation not the Karst with low mountains with terraces round abrasives accumulate along the Son River and river valley at the edge of Lent and limestone center. Other major tectonic type of tectonic Karst is characterized by the ancient tropical karst mainly from Mezozoic, but 2/3 of the area is karst from Dai Tan Sinh. Limestone occupies an area of 200,000 hectares, with a similar region in Kham Muon province of Laos. Karst tectonic processes have created numerous features such as underground rivers, the dry up, the terraced dynamic, active suspension, active and dynamic tree intersected. The work has been divided into 9 dynamic river system flowing into the river Son Phong Nha and 8 of powertrain dome into the river Lent.

Compared with other karst areas in the world have been recognized as world heritage area, Phong Nha-Ke Bang natural characteristics are more differences due to climatic conditions and different geological structures. Area Phong Nha-Ke Bang in orogenic belts Alpi, a young mountain belts grow strongly in the Cenozoic era. Therefore, the limestone blocks in this area are quite strong mechanical deformation due to faulting. Regional climate is tropical monsoon should karst phenomena here unlike temperate areas of strength as well as the process of karst terrain types that it creates on the surface and underground areas.

Interlaced fault system on the limestone in the area of Phong Nha-Ke Bang facilitate easy infiltration of water into the rocks increases solubility in water due to acid substances react with limestone (calcium carbonate). Majestic cave system of Phong Nha is generated by the process of tectonic fractures, then the process of physical weathering and chemical eats, dissolved, washed away over millions of years. In humid tropical conditions, the process of very strong Karst intensity and speed of destruction. Besides karst system, mountainous land with rocks background mainly acid magma rock, clay, silt and rock metamorphic neck.

Soils, Phong Nha area has many corrupt land formed from the different source rocks. Ferarit land mostly barren ground limestone, gold Feralit land on acid igneous rocks, soil and light yellow Ferarit alluvial land along the river.

Area Phong Nha-Ke Bang cave oldest age Southeast Asia, with the start time cave was formed 35 million years ago in conjunction with the extension phase formed the South China Sea. The running direction of the cave system in the area of Phong Nha-Ke Bang direction faults coincide with regional and local authorities.

Floods in the valley area occurred from September to November, but during the dry season from February to August, almost dried out streams.

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