China’s hidden doomsday: 140-million-year old supervolcano found under Hong Kong revealed - Express.co.uk

A supervolcano is a large volcano that has had an eruption with a Volcanic Explosivity Index (VEI) of eight, the largest recorded value on the index.

The geology of Hong Kong is dominated by igneous rocks, including granitic rocks and volcanic rocks, formed during a major volcanic eruption period in the Mesozoic era and researchers say the origins of the city can be traced back to the lava and ash left behind after a supervolcano eruption 140 million years ago in the area.

He said: “The ‘ah-ha’ moment for me was realising that everything pointed to one source – a supervolcano – the one system that could have preserved all the unique geological features of Hong Kong.

The team then mapped out its entire system, running from eastern Sai Kung to Kowloon and Hong Kong Island itself, formed by the lava and ash left behind and named it the ‘High Island Supervolcano’ after the Sai Kung island, which marks the volcano’s top edge.

The 18-kilometre-wide caldera of the supervolcano was formed as high pressure and heat at the Earth’s core caused the surface to collapse and the deepest part of the volcano remains below the middle of the city, in Kowloon and Hong Kong Island, where leftover pockets of magma are marked out in the form of granite

The hexagonal volcanic pillars covering a large area of eastern Sai Kung were formed as the thick layer of volcanic ash cooled and contracted