The imposing karst structures which give Ha Long Bay its distinctive beauty have been evolving over the course of over 20 million years, and the history of the tectonic movement can be traced back as far as 500 million years. Up to 500 million years BC, Ha Long Bay was a deep sea, but this changed as the area moved into the Carboniferous and Permian periods, around 340-250 million years BC.
The bay then went from being an area of deep water to a shallow one as a result of tectonic movement which lifted the whole area. For approximately the next 100 million years, the two types of limestone were under formation, a thick layer of 750 m and a thinner layer of 450 m.
After this came a period when the area was made up of high, mountainous land which was then carved into smaller chunks over millions of years of erosion from both the weather and tides. In comparison to the whole process, the caves were only formed relatively recently, between 68,000 to 9000 years BC.
The unique pairing of tectonic movement, geological makeup, and weather and tide conditions have combined to create the fascinating and awe-inspiring landscapes of Ha Long Bay, Lan Ha Bay and Bai Tu Long BaySave