Chinese authorities revealed last week that much of Hong Kong and its Victoria Harbour, including this rocky islet, lies atop the remnants of an ancient supervolcano with an 11-mile (18 kilometer) wide caldera.
Calm down, it poses no risk to today’s millions of Hong Kong residents, it’s been extinct since it last erupted and largely collapsed into the ocean 140 million years ago, Hong Kong’s Geotechnical Engineering and Development Department said.
In fact, geologist Denise Tang said in a state-sponsored broadcast, the biggest risk is to tourists trying to visit the rocky islands by boat.
“There are no facilities here so we cannot recommend trying to land,” she said.
Hong Kong’s newly identified volcanic islands are known as the Ninepin Group or the Kwo Chau chain. The volcano as a whole has been dubbed the High Island Supervolcano.
The islands represent only part of the volcano’s hardened lava, much of which is either beneath the sea or long since eroded away.
“This discovery is very important, not only because we have discovered huge volumes of materials that have been erupted, but we know the magma source,” Tang told the Hong Kong news agency. That source, she added, is preserved as the granite rocks on the northern part of Hong Kong island itself.
Among the striking features of the Hong Kong supervolcano are hexagonal columns of rock, like these pictured in a close-up of an island cliff.
Such columns form in rapidly hardening lava flows, as the cooling material shrinks. Later, as the lava mounds erode, rocks break along joints between columns, producing a sharply layered texture.
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via: NatGeo
