Monday 17 December 2018

Super-volcano eruption 'could kill 100 million'

Volcanic lightning at an eruption of Mount Sakurajimain the Kagoshima prefecture in southwestern Japan in 2016
Volcanic lightning at an eruption of Mount Sakurajimain the Kagoshima prefecture in southwestern Japan in 2016

Julian Ryall

A lava dome discovered in the Pacific Ocean off southern Japan contains more than 7.5 cubic miles of volcanic magma and could kill as many as 100 million people if it erupts, according to Japanese scientists.

In a paper published in Scientific Reports, researchers at the Kobe Ocean Bottom Exploration Centre reported that the lava dome - one of the largest ever discovered in the world - is expanding within the Kikai Caldera, an undersea volcano just over 30 miles from the southern tip of Kyushu, the most southerly of Japan's main islands.

The dome stands nearly 2,000ft proud of the seabed and is now a mere 100ft beneath the surface. It is more than six miles in diameter and occupies a massive hollow within the caldera that was created by a volcanic supereruption about 7,300 years ago.

That eruption is believed to have wiped out the prehistoric Jomon civilisation in southern Japan.

Distortions in the surface of the feature have led researchers to conclude that lava is building up beneath the dome, a suspicion heightened by plumes of superheated water and bubbling around the caldera.

The scientists have determined that the Japanese archipelago has experienced 10 massive caldera eruptions over the last 120,000 years.

As well as ejecting huge amounts of debris into the atmosphere, potentially blocking out the sun for parts of the planet, a new super-eruption would cause a massive tsunami that would strike southern Japan and the coasts of China and Taiwan.

The wave would also spread rapidly across the Pacific, causing devastation in low-lying island nations before striking the coasts of North and South America.

The paper points out that super-eruptions that trigger the collapse of a large caldera are "rare but extremely hazardous events, and also have severe global impacts such as 'volcanic winter'.

"Many of these super-volcanoes repeat super-eruptions in their multi-million year histories", the report said, adding that the scientists hope to be able to use their research in "preparation for the next super-eruption".

Japan sits atop a number of tectonic plates and is one of the most seismically active regions in the world. There are 111 active volcanoes across the nation, of which seven have been confirmed to be prone to periodic super-eruptions. The entire Japanese archipelago - which sits on the Pacific "Ring of Fire" - is also highly susceptible to earthquakes.

The Kikai Caldera lies on a fault line that runs through the centre of Kyushu and has seen a number of recent serious earthquakes. In April 2016, 41 people died in a magnitude 7.3 earthquake that struck Kumamoto Prefecture, with several more killed in aftershocks.

© Daily Telegraph, London

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