Phong Nha – Ke Bang National Park lies in Quang Binh Province – the central Viet Nam. Covering an area of more than 343,000 hectares (heart zone of 123,300ha and buffer zone of 220,000ha), Phong Nha – Ke Bang situated in Quang Ninh, Bo Trach and Minh Hoa districts, is 50km northwest of Dong Hoi City.
Phong Nha – Ke Bang can be compared to a huge geological museum thanks to its complicated geological structure with different categories of stone including sandstone, quartz, schist, siliceous limestone, granite, granodiorite, diorite, applet, pegmatite, etc. Phong Nha-Ke Bang is the oldest and largest tropical karst formed 400 million years during the main geological periods of the Earth, bearing the original topographic and geologic characteristics. Experiencing major tectonic phases, high mountain ranges and the depressed sedimentary basins were formed. These fluctuations have also contributed to the diversity of geology, topography, geomorphology.
Phong Nha – Ke Bang karst mountains can provide a lot of valuable information about the Earth’s prolonged geological process through various periods, from the Ordovician Age – Silurian Age (about 463.9 – 430 million year ago) to the Quaternary Age (1.75 million years ago). It is also noteworthy to mention a geological characteristic – the system of underground rivers and grottos in limestone mountains.
In the non-karst geomorphologic area, there are many low mountains covered by a floristic carpet. The erosion has created a number of abrasion-accumulation terraces along the valleys of the Son and Chay rivers and at the margins of the central limestone massifs. The transition terrain consists of a diversity of rock intercalated by limestone mountains.