NZ-led 'super-eruption' study asking when, where and how big next one will be

Lake Taupo, as we know it today, fills the hole left by the world's most recent supervolcano eruption. Photo / Alan Gibson

The possibility of a New Zealand "super-eruption" naturally conjures up apocalyptic imagery.

We think of towering, high-speed surges of hot gas and debris laying waste to entire landscapes in every direction, and huge black ash clouds visible from the other side of the planet.

Now, a Kiwi scientist is leading a new $8.2 million, five-year study to clear up some of the uncertainty - and hype - that comes with the risk posed by supervolcanoes.

Super-eruptions are extremely rare: in the past 2.8 million years, there have been only 10 of them recorded, four of them in our Central North Island.

Lake Taupo essentially fills the hole left by the most recent of these monster blows - the Oruanui eruption, more than 25,400 years ago - which spewed 530 cubic km of molten rock into the atmosphere and spread ash as far as Antarctica.

Today, scientists think of the whole area of volcanic activity between Kawerau and Tokaanu as one single but complex supervolcano system, which last saw a bout of unrest at Taupo in 2008.

Victoria University volcanologist Professor Colin Wilson has spent decades researching the Taupo and other ancient eruptions from volcanoes in the region.

"We are very confident that these volcanoes are still alive," he said.

Wilson expects these will experience more episodes of unrest, perhaps every decade, but eruptions are far less frequent, occurring every 500 to 1000 years.

"Supervolcano eruptions in New Zealand and globally are rare but extremely hazardous events with the potential, in the worst case, to cause global-scale disasters and even bring our already stressed global society beyond the limits of sustainability."

Yet, around the world, there was a degree of hype surrounding these structures - the Yellowstone Caldera in the US, particularly - that could trigger panic and over-reaction with the slightest bit of activity.

"Our research programme is thus designed to provide the knowledge with which to reduce the uncertainty around future supervolcano unrest events and eruptions not just in New Zealand but globally."

Among more than 30 experts working on the project, supported by a grant from the Government's Endeavour Fund, are a group of Italian scientists who have been researching Campi Flegrei, a major volcano near Naples that has behaved similarly to Taupo.

Volcanologist Professor Colin Wilson is leading a new $8.2 million study investigating the risk of a supervolcano eruption. Photo / File

The team ultimately hope to create a new model allowing scientists to forecast whether unrest will lead to eruptions, to better estimate the size and timing of future events, and pinpoint how much warning might be given.

That meant trying to work out, in as much detail as possible, what occurred in previous big New Zealand eruptions.

"We are world leaders in developing the methods for working out where the molten rock was stored, how fast it became ready to erupt and estimating how rapidly magma rose to the surface in past eruptions," Wilson said.

"We want to refine this knowledge and link it with geophysical approaches to determine the current state of the system and our ability to track changes of the presently quiet volcanoes into unrest and eruption."

It also involved identifying those "tipping points" that could take supervolcanoes from a dormant state to an active one.

"Only about one in 30 unrest events will be followed up by an eruption. Can we tell the difference?"

Geological studies have indicated that faulting and rifting taking place deep beneath the central North Island had some influence, meaning Wilson and his colleagues would also have to look at processes outside the volcanoes themselves.

Another big hurdle was the fact each eruption was unique - something the team would have to tackle by looking at various scenarios and weighting them depending on how likely they were to occur.

"It's important to be able to provide more accurate forecasting about future events because uncertainty is a huge problem in today's New Zealand society," Wilson said.

"If Taupo or Okataina become restive, the potential effects on the New Zealand economy are severe because of the perception of what these volcanoes are and are capable of doing."

That wasn't to say these volcanoes hadn't produced devastating eruptions in the past.

"In contrast, it's to say that the chance of such devastation in the future is low and our work is aimed at producing the time-scales over which response can be made.

"If, in doing this work, we can show the world how to tackle the problem of large volcanoes and their future eruptions we will have been able to benefit society globally."