Tam Giao Cave - Ninh Bình Province

Limestone mountainous areas in Vietnam have beautiful landscapes and marvellous caves and grottos. Geographically, the country has a fairly well developed system of limestone mountains with unique terrain and scenes, accounting for nearly 20% of the mainland’s area.

According to geologists, Vietnam has limestone groups which formed during the Mid-Cambri to Mid-Devon eras (about 500-520 million years ago). Their formation created caves and grottos, which are from dozens to hundreds of metres deep and have simple and complicated compositions. Examples are the Cong Nuoc Cave in Tam Duong, Lai Chau Province, 602m deep and the Phong Nha-Ke Bang system of caves and grottos in Quang Binh Province, several dozens of metres long. Many big rocks have limestone artesian water running inside, creating gigantic underground rivers. The calcium precipitates (CaCo3) in the caves and grottos create stalactites and stalagmites looking like bells, curtains, screens and pillars.

The Phong Nha system of caves and grottos has a total length of more than 40km. Phong Nha Cave alone is 7.7km long and consists of 14 separate caves created by limestone-dissolved underground rivers. In some places, the caves are connected and are above and below ground.

The limestone mountainous areas also have a unique and diverse ecological system with rare and precious fauna and flora. Now that the natural preservation and environmental protection have become important issues, these areas provide an opportunity to achieve a harmony between development and preservation.

Caves and grottos serve as a live museum of humankind, where people can find vestiges of extinct species of animals and plants, relics of pre-historic people as well as layers of rocks and geological stratums that experienced changes millions of years ago. Limestone caves with human remnants have been discovered and researched in many areas, such as Lang Son, Yen Bai and Hoa Binh Provinces. In the layers of sediments in a cave in Man Duc, Hoa Binh Province, researchers have found many fossil remains of Hmoerlotus and Honosapien pre-historic people, some species of mammals plus tools for construction, hunting and cooking.

Today, people can explain the mysterious sounds in the caves caused by the underground boils which are likened to the persona of ghosts and devils. Humid and hot air evaporating from the cave meets the normal atmosphere pressure and make sounds associated to the “puffs” of monsters.

In Cam Nuong, Thanh Hoa Province there is a species of carp living in the grottos. Their eyesight is nearly gone so they live only around the well lit entrance of the grottos and never venture far to the river. That’s why the local people call them genie fish.

Vietnamese limestone mountains areas have a terrain full of obstacles. They flourish with magnificent caves and grottos plus a unique and diverse ecological system, creating beautiful and fascinating surroundings. These areas contain the flora, rich in quantity and species with high density. Some of the rare and precious species of animals recorded in the Vietnamese Red Book, such as Sao la (Pseudory nghentinhenis), monkeys, gibbon and Vooc (Spider-monkey) can only be seen in these areas. On an area covering 220sq.km in Cuc Phuong forest in Ninh Binh Province there are 1,944 species of primates belonging to 224 families. Phong Nha-Ke Bang area has 876 species of primates and 259 species of butterflies. Ba Be-Bac Kan limestone area covering 137sq.km has up to 417 species of animals and plants.

The system of limestone mountains has great tourism potential, such as ecological tourism, geographical tourism and adventure tourism. Limestone mountainous areas are home to ethnic groups with diverse and distinctive cultures. Together with splendid landscapes and cultural-social characters, Vietnam’s underground caves and grottos bring surprises and pleasures to people who are fond of discovering this land.

Vietnamese and Belgian geologists undertake a survey on Cam Khuay Cave in Thac Ba (Yen Bai).	Studying the changes of the limestone mountains.	Geologists find a river in an underground cave.
Tam Coc 1 area in Tam Coc-Bich Dong tourist site (Ninh Binh).	Tam Coc-Bich Dong tourist site in Ninh Binh abounds with beautiful caves and grottos.	Stalactites in Noong Khac Cave in Yen Minh (Ha Giang).

(Source: VNA)