The imposing karst structures that give Ha Long Bay its distinctive beauty have been evolving over the course of more than 20 million years, and the history of the tectonic movement can be traced as far back as 500 million years. Up to 500 million years ago, the bay was just part of the ocean, but this during the Carboniferous and Permian periods, around 340-250 million years ago.
The sun getting ready to set over Ha Long Bay
The area of the bay then underwent a change from deep waters to shallow ones as a result of tectonic movement that lifted the whole area. For the next 100 million years or so, the two different types of limestone were under formation, a thick layer of 750m and a thinner one of 450m.
The islands range from smaller rock formations to giant mountains
The area was then made up of mountainous land which was then slowly carved into the smaller islets we see today over the course of millions of years of erosion. Relative to the whole process, the caves are young, most of them being formed between 68000 BC and 9000BC.
One of the many unique islets of the bay
The unique pairing of tectonic movement, geological makeup, 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 Bay