[Explanation] Recently, the Agriculture, Fisheries and Conservation Department of the Hong Kong Special Administrative Region Government announced that the Early Cretaceous rhyolite column group located in the Hong Kong UNESCO Global Geopark was selected as the first 100 geological heritage sites of the International Federation of Geological Sciences.
The reporter learned through field visits that the Early Cretaceous rhyolite column group found along the coast of Sai Kung and many nearby islands is called the Liangchuanwan Formation, and it was included in the Hong Kong Geopark in 2009.
The rock pillars here are large in number, large in size, well-preserved, and widely distributed. It is a rare and most representative geological wonder in the world.
[Concurrent] Chen Yulan, Director of Advanced Geopark, Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government
In fact, there are also hexagonal columns in other places, but most of them are formed of basalt, and its siliceous content is relatively low.
However, this kind of rock in Hong Kong is a rhyolite volcanic rock, which is a relatively high siliceous content, with a siliceous content of 76%, which is rare in this world, and the hexagonal column in Hong Kong is compared with other places. , Its rock pillars are relatively large, with an average diameter of 1.2 meters to 3 meters, a rough height of up to 100 meters, and a wide coverage area, which can reach 100 square kilometers.
[Explanation] The reporter found through field visits that from a distance, these rock pillars are neatly arranged in stripes, and the cross-section of each rock pillar is hexagonal.
Chen Yulan told reporters that this was due to the formation of a large volcano in the southeast of Hong Kong caused by intense crustal activity about 140 million years ago.
The eruption spewed a large amount of ash and lava, and the volcano finally collapsed to form a caldera with a diameter of about 20 kilometers.
A large amount of volcanic material accumulated in the caldera and slowly cooled and contracted, eventually forming a hexagonal volcanic rock column.
[Concurrent] Chen Yulan, Director of Advanced Geopark, Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government
In fact, this is a physical phenomenon, because the volcanic material is accumulated in a caldera, and it will shrink when it cools. If the volcanic material is very uniform and the environment in which it shrinks is very stable, it will shrink. Slowly go down (extrusion) from the uppermost cooling surface, and when it shrinks, it can (extrusion) form this hexagonal square column.
[Commentary] Chen Yulan said that the Liangchuanwan Formation was selected as one of the first 100 geological heritage sites of the International Federation of Geosciences and Technology, which represented its international importance and was recognized. It is hoped that more Hong Kong citizens will know about these rare geological heritage in the future.
[Concurrent] Chen Yulan, Director of Advanced Geopark, Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government
Hong Kong is honored to have such a precious geological heritage, which is one of the 100 most important geological heritages in the world.
I hope that the people of Hong Kong and others will join me in getting to know and cherish our precious natural heritage.
Reporter Luo Siyu reports from Hong Kong
Responsible editor: [Li Ji]