Halong Bay has some of the most breathless scenery the world has to offer, much of this bang-up natural beauty is thanks to the brilliant rock formations that dominate the true laurel ’ mho landscape .

A Million-Year Journey

The formation of Halong Bay dates to over 500 million years ago. Over time the bay has gone through countless changes resulting in the brilliant natural curiosity we have today. The beautiful ancient marine limestone rocks used to stand at over 1,000 meters grandiloquent. Millions of years of erosion have reduced them to their present size. According to researchers and respect geologists, the Halong bay we see now was formed roughly 8,000 years ago dating back to a period in our earth ’ sulfur history called ‘ The Middle Holocene Transgression ’. This refers to a ‘ marine transgression ’ ; a prison term when the sea rose to a point much higher than they reach nowadays frankincense making the shorelines higher and causing flood. Limestone batch in Halong bay.

Halong Bay and the encompassing area are made up of chiefly of thick limestone, precisely like the celebrated limestone karsts that can be seen sprouting majestically throughout the alcove ’ south waters. The limestone that is found in Halong Bay began forming during the Carboniferous period, around 340 million years ago. At this point, the Earth was a lot warmer and wetter than it is today, and due to bombastic swamps carbonate sediment moved into the oceans. This resulted in the gradual hardening and thickening of the limestone over many millions of years. This limestone achieved a thickness of 1,200 meters, and these are the celebrated karsts that we see nowadays. Thanks to these millions of years of erosion from the rain and the ocean, Halong Bay is besides home to unique valleys and an impressive tangle of caves ! The oldest of these caves are called ‘ Phreatic Caves ’ and tend to be found at the highest levels. These Phraetic caves include the celebrated and competently named ‘ Sung Sot ’ cave, which means ‘ Surprise cave. Sung Sot is one of the biggest and most brilliant of all the caves in Halong Bay.

Sung Sot ( Surprise ) cave

Geological Feature

Another stunning geological feature of Halong Bay is the Ba Ham lake system. The Ba Ham lakes are a system of underground lakes connected by hide caves and created completely by sea erosion. Above these lakes there are hanging stalactites – stalactites are formed when urine containing calcium bicarbonate drips from the ceiling of a limestone cave. Over thousands of years, these calcium bicarbonate deposits build up to form perfect stalactite and stalagmite pairs. Kayaking through Ba Ham lake ( Photo : Shutterstock ) According to Dr. Tran Duc Thanh, of the Haiphong Institute of Oceanology, and Dr. Tony Waltham, a geologist at Nottingham Trent University, the landscape of Halong Bay is of “ international significance and of fundamental importance to the skill of geo-morphology ”. The karsts found in Halong Bay are a brilliant exercise of the development of a limestone landscape over millions of years and the fact of the marine transgression which caused the extreme ocean corrosion on these karsts makes Halong Bay about unique. This must not be taken for grant and must be conserved as an crucial part of world heritage .


  • 1. Thanh, T. D, N. Can and D. D. Nga. 1997. Coastal development of Do Son – Ha Long Area during Holocene. In: Marine Geology and Geophysics. Sci and Tech. Pub. House. Ha Noi. p. 199 – 212