Why super volcanoes are millions of years in the making

Gigantic super eruptions are so rare because of the extraordinary length of time they take to build up

Using the crustal flow model, scientists now have a better understanding of why volcanoes such as Mauna Loa erupt. Photo: George Rose

Magma massing over millions of years before swiftly — in relative terms — heading for the Earth's surface cause volcanic super eruptions, researchers have found.

Such eruptions are very rare and Bristol scientists estimate only one occurs on Earth every 20,000 years. However, they are highly destructive locally and can create severe climate change on a global scale that would have catastrophic consequences.

The research was published in the Nature journal on Thursday, with volcanoes already in the news after the eruption of Mount Fagradalsfjall near Iceland's capital Reykjavik on Wednesday.

An international team at the University of Bristol and the Scottish Universities Environmental Research Centre set out to show how four known super eruptions were caused, using models of rock movements in the Earth's crust.

They found the magma took millions of years to form, yet once it finally disrupted the crust it then erupted within mere decades.

They happen so rarely because of the extraordinarily long time they take to build up.

“By studying the age and character of tiny crystals erupted with molten rock, we can help understand how such eruptions happen," said Prof Steve Sparks of Bristol’s School of Earth Sciences.

“The research provides an advance in understanding the geological circumstances that enable super eruptions to take place. This will help identify volcanoes that have potential for future super eruptions.”

Iceland volcano silver lining

The eruption of Mount Fagradalsfjall did not qualify as a super eruption. Such was its benign nature, the country’s tourism industry has used it to try to revive its flagging fortunes after the pandemic had banished most visitors from the Atlantic island nation for more than two years.

With reports of sightings of lava, the shares of Icelandic airlines Icelandair hf and Fly Play hf, which flies under the banner Play Air, began ticking up. Within hours of magma appearing, Play Air was already advertising the eruption on its website, describing it as “peaceful” and “picturesque.”

“There are not many things that can beat having an eruption an easy distance from your hotel and airport bar, so this is extremely positive,” Birgir Jonsson, chief executive of Play Air, said by phone. “We saw already yesterday that the traffic into our booking system and all our social media greatly increased. So I believe this is exactly what the doctor prescribed especially when going into the fall and winter season.”

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