Experts try to forecast NZ big bang

White Island, off the coast of the Bay of Plenty, is still in an eruptive cycle, and scientists are trying to work out which volcano will be next.

When is our next big bang?

That's the explosive question a team of scientists are going to try to answer, by using maths to calculate the estimated time and size of the next eruption of each of New Zealand's 10 main volcano centres.

Our most recent eruptions have taken place at White Island, still in an eruptive cycle, at Mt Tongariro twice in 2012, and at Mt Ruapehu eight years ago, when a large lahar was sent rolling through the western boundary of Whakapapa skifield.

But outside these regularly active volcanoes, a greater concern is when we're likely to see the next blow at quiet mountains such as Mt Taranaki, which has a 50 per cent probability of erupting in the next 50 years, or at one of Auckland's long-silent field of 50 volcanoes.

More worrying still is the thought of an eruption at one of the huge caldera volcanoes in the Central North Island.

Our best-known example, the Hatepe or Taupo eruption around 1800 years ago, would have created effects visible in China and Rome and fired a devastating 1.5km-high pyroclastic flow that covered the landscape with ash and pumice for a distance of 80km.

To create a new probability model, Professor Mark Bebbington of Massey University will poll experts to form a consensus view.

And he will also build a dataset of historical records from similar volcanoes worldwide.

"We've got quite a number of volcanoes in New Zealand, some of which haven't erupted for quite a while, like Mt Taranaki," he said.

"But there are analogues - volcanoes that look very similar and erupt similar products in similar settings, which have been more active recently."

One example was Mt Merapi in Indonesia. Before it erupted in 2010, killing 353 people, it had a long quiet past, just like Mt Taranaki.

"So the idea is if we can work out how the two records can map on to one another, then we can extend it to other ones worldwide."

Another Massey University scientist, Dr Gert Lube, who specialises in devastating pyroclastic surges, is starting another study with colleagues here and overseas which will use a large-scale eruption simulator based at the Manawatu campus to understand what happens to infrastructure when it is hit by a volcanic current.

Research published last month found a catastrophic volcanic eruption in Auckland's industrial heart could have an economic impact of up to $10 billion in the first year and knock out a large chunk of the city's GDP.