Mentioning about Halong, ones would not hesitate to use the most beautiful words to describe the breathtaking natural scenery of the Bay. Besides the unique natural scenery, the bay has a great geological value.
The long-lasting history of geological formation of Halong Bay is known with more than 500 million years of changes between mountain growing, marine degradation, mountain sinking, and encroaching sea. Halong used to be a very deep sea during Odovic – Silua era, shallow sea during Cacbon – Pecmi era, and coastal area during Plaogen – Neogen era. Not only that, contributing on the present natural wonder Halong Bay was the result of a magnificent ancient marine limestone accumulation, which reached above 1,000 meters 340-240 million years ago, and the Karst erosion period of more than 20 million years.
Halong Bay was also an excellent example for Karst period of developing and dominating under the humid tropical weather of Vietnam. The bay went through the Karst evolution in million years, due to the combination of geological and climatic factors like thick limestone in association with tropical climate, and finally the slow tectonic uplift in general.
In addition, the permanent erosion process of rain and tides from the sea resulted into special geological formation of the most unique valleys, Karst lakes and towers in the world, and a complicated system of primitive caves. This system is separated into three main forms: developing vertically, for example the highest and most ancient caves that can be seen now; developing horizontally, which resulted into middle-age caves; and the final form is composed due to the cutting and erosion of water streams, which provides priceless biological, geological and oceanographic values.
Thanks to the early development of geological system, Halong Bay is preferred by the Mother Nature with a stable foundation to develop other values like biology, culture, archeology, and history. Amongst which, biodiversity is the strength, as well as an attractive factor to draw international visitors to come and explore. Halong is a giant conservation zone of floral kind, especially rarest species in the world. The Bay is also a base of a variety of the tropical ecosystem such as mangrove ecosystem, reef ecosystem, and tùng áng ecosystem.