Hong Kong’s hexagonal volcanic rock columns have been selected as one of the First 100 International Union of Geological Sciences Geological Heritage Sites. The inclusion of the rock formations, which are in the Hong Kong UNESCO Global Geopark in Sai Kung, will be announced between October 25 and October 28.

The rock columns seen on Ninepin Group.
The rock columns seen on the Ninepin Group (© GovHK)

The rock columns, known as the High Island Formation, date back to the Early Cretaceous period. Geologists believe they were formed because of volcanic activities in the region around 140 million years ago. They are spread over areas on Sai Kung East Country Park’s High Island, Kau Sai Chau, Jin Island, the Ung Kong Group and the Ninepin Group, and cover about 100 square kilometres on land and under the sea.

According to a spokesperson from the Agricultural, Fisheries and Conservation Department, “The formation comprises a great number of columns, which are large, well preserved and widely distributed, making it a globally rare and iconic geological wonder.” In addition, hexagonal rock columns in other parts of the world are usually made up of dark grey basalt with low silica content. In contrast, the High Island Formation is composed of light-coloured silica-rich rhyolitic volcanic rock.

A cross-section of the hexagonal rock columns on Ngan Peng Tau, North Ninepin Island
A cross-section of the hexagonal rock columns on Ngan Peng Tau, North Ninepin Island (© GovHK)

This year’s list considered submissions from 181 sites from 56 countries. These sites were selected to recognise geological heritage sites of high international scientific significance around the world to promote their conservation, education, and geotourism. The project is a collaboration between UNESCO’s International Geoscience and Geoparks Programme, geological survey institution, and research institutions around the world.

Header image credits: GovHK

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From the Middle East to the Far East and a couple of places in between, Anjali has lived in no fewer than seven cities in Asia, and has travelled extensively in the region. She worked as a lifestyle journalist in India before coming to Hong Kong, where her favourite thing to do is island-hopping with her daughter. You can check out her musings on motherhood, courtesy her Instagram profile.

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