Geology of East Dam: Relics of a SuperVolcano
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The photo shows High Island in Sai Kung, Hong Kong, identified by geologists as the actual site of a supervolcano that erupted around 143 million years ago. This ancient SuperVolcano shaped the Sai Kung’s unique hexagonal rock columns, which is largest in the world and volcanic landscape, now part of the Hong Kong UNESCO Global Geopark.
Volcanic Rock from 140 million Years Ago
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S-shaped Hexagonal Volcanic Rock Columns
Unlike the typical straight hexagonal columns, these columns were buckled and distorted into an S-shape due to earthquakes and regional fault movements before the magma fully cooled and solidified.
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Hexagonal Volcanic Rock Columns
when thick volcanic ash and lava cooled and contracted, creating striking hexagonal fractures. These large, well-preserved columns, some up to 3 meters wide, are part of the world's largest coverage of such formations.
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World's Largest Hexagonal Volcanic Rock Columns
If you want to see the full scope of why Hong Kong has the world's largest hexagonal volcanic rock columns, join our boat sightseeing tour! The tour will take you through the top 8 geo-wonder attractions in Hong Kong Geopark!
Other Attractions in East Dam
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Kwun Mun Sea Cave
Kwun Mun Sea Cave, named after the original Kwun Mun Channel, is the only sea cave visible after the East Dam blocked the strait. Once part of a bustling waterway with many villagers living nearby, it now stands as a unique geological feature, showcasing natural coastal erosion and historical significance.
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Dolosse
Anchor-shaped concrete prefabricated components (dolosse) in East Dam are large, interlocking blocks placed along the breakwater to absorb and dissipate wave energy, protecting the dam structure from strong sea waves and erosion.
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Mole Holes
The circular holes between the anchor-shaped breakwater and the main dam at High Island Reservoir East Dam are designed to reinforce the breakwater’s stability. These “mole holes” slow down water flow, reducing wave impact and protecting the dam structure.
History of East Dam
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Sai Kung 400 Years Ago in 16 Century
The story of Sai Kung began 400 years ago in what is now the High Island Reservoir. Before the reservoir was constructed, this area was known as the Kwun Mun Channel, a waterway bordered by several villages, including Lan Nai Wan, Kwun Mun, and Sha Tsui.
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The Lan Nai Wan Village
Among these, Lan Nai Wan Village boasts a history of over 400 years, with approximately 50 households and around 400 Hakka residents who relied on agriculture and fishing for their livelihoods.
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Construction of High Island Reservoir
BOOK NOWIn the late 1960s, the Hong Kong government announced plans to construct the High Island Reservoir to address water shortages. This development necessitated the relocation of several villages.
