Quick Dips

Sitting on a Volcano

Auckland sits on an active volcanic field that could produce a new volcano at any time, according to researchers from the Institute of Geological and Nuclear Sciences (GNS), who are working with the Auckland Regional Council to better understand the field and the hazards it poses.

"Scenarios being considered include an eruption forming an offshore island, one in the Tamaki Estuary and three within two kilometres of the central business district," says project co-ordinator Dr David Johnston. "Each case is expected to result in the evacuation of 100,000 to 150,000 people and major disruption to commerce and services."

The group has developed five realistic eruption scenarios to illustrate what could happen to Auckland's population, infrastructure and environment. The research has also noted the importance of building relationships among a range of organisations and community agencies representing vulnerable groups.

Johnston says the first of Auckland's 50 volcanoes started to appear about 140,000 years ago.

"The life of the volcanic field is estimated at one million years so, geologically speaking, the field is still young. There has been a trend to bigger and more frequent eruptions around Auckland in the past 20,000 years. Rangitoto, the youngest and biggest volcano, formed about 600 years ago."

"The lack of surface activity can lead to the false impression that the Auckland volcanic field is extinct. But the hot spot of magma deep below the city remains active and will almost certainly send up another volcano in the future."

"The next eruption is unlikely to occur at an existing volcano. Auckland tends to produce "single episode" volcanoes -- after the eruption the volcanic plumbing seals off and blocks the flow of future magma."

GNS, along with Massey University, is also researching how much people know and understand about the vulnerability of New Zealand to natural hazards. They are also evaluating methods of improving the effectiveness of hazard education programmes.