Model reveals vulnerable Auckland suburbs include Three Kings and Mangere

Models have laid bare the threat explosive volcanic activity poses to our largest city, with Three Kings and Mangere among the Auckland suburbs most vulnerable to devastating, high-powered blasts.

Past maps, created by a Massey University researcher, show which areas are more at risk from a violent kind of eruption that can send a turbulent cocktail of gas, steam and fragments roaring from the ground. These events are sparked when magma mixes with water from the sea or underground, causing an explosion.

Scientists have shown how more than three quarters of the 52 volcanoes in the vast Auckland Volcanic Field bear ancient evidence of such activity.

To expose potential future danger spots, researcher Gabor Kereszturi drew upon a combination of geological data and previous research.

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This map shows areas in Auckland at risk of a certain type of violent volcanic explosion

Multiple layers of information were combined using a technique called Geographic Information Systems, or GIS, which ultimately allowed him to score susceptibility in different areas from one to 10.

Suburbs including Three Kings and Mangere had a higher chance of explosive volcanic activity than other areas like the elevated areas of North Shore. Areas of moderate risk include Favona and Otahuhu, while Glenfield and Chatswood were among the safest areas.

Dr Kereszturi's model showed how fault lines - in which more water could flow amid porous rock - were hot spots for violent eruptions.

Dr Kereszturi said a GIS approach to the situation was powerful, as each layer of data added made for a clearer picture of volcanic hazard.

"Forecasting where the next eruption is going to occur is challenging," he said. "But by creating a model based on many different types of information we have readily available, it allows us to predict how a potential future volcano in Auckland might erupt and how big an area it would impact."

The next step was to gather information about the urban objects like buildings and infrastructure and add these to the model.

"The more information we keep collecting, the better these models will become."

The impact of volcanic eruption in Auckland could be catastrophic - a worst-case eruption near the CBD could cause a 47 per cent reduction in gross domestic product.

Civil Defence planners say warning signals would likely provide more than enough time for mass evacuation.