Aucklanders have been warned that they cannot be complacent about the risk of volcanoes and that a serious eruption could cause large-scale destruction and force the evacuation of 450,000 people in the region.
Experts say an eruption in the Auckland volcanic field is a "low probability, high consequence" event but city-dwellers would only have days to prepare.
Scientists, civil defence experts, academics, and council staff were in the city yesterday for the Managing Volcanic Risk in Auckland forum, pooling their knowledge to plan for a possible city-wide disaster.
Civil Defence Minister Nikki Kaye opened the forum, spelling out possible consequences for Auckland in the event of an eruption.
"If we look at possible effects on Auckland these could include the devastation of buildings and infrastructure, large economic losses, a reduction in air and rail services, disruption to vital lifeline services, and increased health risks from ash and dust," she said.
Experts could not prevent an eruption, or predict exactly when one might occur, but the most recent eruption in the Auckland volcanic field was Rangitoto, about 550 years ago, she said.
Auckland City Council civil defence controller Clive Manley said although agencies were combining efforts to plan for an eruption, it was difficult to tell how the public would react.
Research showed Aucklanders felt safe from natural disasters, and would hesitate before acting to protect themselves, he said.
"It's a huge challenge in getting Auckland to take it seriously."
People saw civil defence staff efficiently managing small-scale storms and did not see a need to prepare for an emergency.
"We're doing such a good job we're making people complacent."
The worst-case scenario eruption could affect a zone within a 5km radius, and up to 450, 000 people.
Aucklanders were the least prepared nationwide for an emergency and only 11 per cent had emergency kits.
GNS volcanologist Brad Scott said there had been between 50 to 55 eruptions in the field over the last 250,000 years, but the results were "variable over that time", and it was not possible to pinpoint when volcanic activity could next occur.
In the case of the Mt Tongariro eruption in August last year, scientists monitored seismic activity once signs of unrest occurred, but were unable to predict the exact eruption time.
Aucklanders could expect days to weeks of warning at most, he said.
"Volcanoes always put their hand up."
Most of the public considered Rangitoto the most prominent volcano because it was "in peoples' face" but it was monitored on an equal footing to all the other volcanos in the field.