Determining Auckland’s volcanic risk

New Zealand’s biggest city is built on a potentially active volcanic field. What risks does this mean for the inhabitants, and how should these risks be managed? Could there be an explosion tomorrow?

Researchers from the DEVORA programme study all aspects of volcanoes, including the chemical composition of their magmas, the deposits they generate and the hazards they pose to Tāmaki Makaurau Auckland.

DEVORA stands for DEtermining VOlcanic Risk in Auckland. DEVORA’s scientists, emergency managers, economists and other experts have following aims:

• Recognise patterns and indicators that signal an impending eruption.

• Identify the biggest volcanic threats to Auckland locally and nationally from future Auckland and other New Zealand eruptions.

• Support the development of risk-management, preparedness, response and recovery plans.

• Educate the public so that our diverse society trusts and understands our science and knows how to act during a volcanic event.

Understanding Auckland’s geology

Auckland was first settled by Māori around 1350, and they valued the land’s ability to grow crops – volcanic soil is rich, containing elements and nutrients essential for plant growth. The many volcanic peaks also made ideal pā sites that were easily defended against invading tribes. Today, Auckland is home to about 1.7 million people. Many are aware they live on a volcanic field and may think the volcanoes are dormant or extinct, but scientists now know that the volcanic field that lies under Auckland is far from dormant. So when will the field erupt again? How often do the volcanoes in Auckland erupt? Does one eruption trigger another?

To answer these questions, scientists are working on a number of projects. For example, Dr Phil Shane from The University of Auckland uses rock cores from areas such as Onepoto Basin to map when different volcanoes have erupted in Auckland. From this data, scientists are working to determine how often eruptions occur and if there are any patterns.

What’s the risk of future eruptions?

GeoNet uses techniques such as gas monitoring, seismic measurements and ground deformation monitoring to monitor all of the volcanoes in New Zealand, including those in Auckland and predict future eruptions. This information will be used to warn about a possible eruption.

Auckland volcanic field

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Auckland is built of an active volcanic field. This map shows the volcanoes from past eruptions.

In 2014, 14 Tūpuna Maunga were returned to Ngā Mana Whenua o Tāmaki Makaurau (the mana whenua tribes of Auckland). The Tūpuna Maunga o Tāmaki Makaurau Authority (Maunga Authority) was established to co-govern these sacred sites.

Map from Volcanoes of Auckland: A field guide, by Bruce Hayward, 2019, Auckland University Press.

Rights: Bruce Hayward

Referencing Hub media

Evidence shows that the oldest Auckland volcanoes erupted about 190,000 years ago (Pupuke and Onepoto), but over half of the eruptions occurred in the last 60,000 years. This suggests that the eruption rate has accelerated, as frequent as several in 1000 years. Based on a median (middle) and modal (most common) gap of about 500 years between past eruptions over the last 60,000 years, it is estimated that the chance of a future eruption in 50 years is roughly 10%. When estimating eruption probabilities in Auckland, we cannot refer to the mean because the few (less common) larger gaps skew the mean value inappropriately. DEVORA research indicates that an eruption of the Auckland Volcanic Field is a low probability event and unlikely to occur in our lifetime. However, given the significant impact such an eruption could have on the city, it remains important for both the public to be aware of and authorities to be preparing for.

Managing the risk

What would happen if a volcano did erupt in Auckland tomorrow? Imagine having a volcano erupt in your backyard that throws up ash and rocks. How would Auckland respond? How would the rest of the country be affected? Scientists are working with organisations such as Auckland Emergency Management and critical infrastructure organisations and businesses, (water and electricity for example) to make sure Auckland is ready. If an eruption did occur in Auckland, all these groups would be involved to try and minimise the impact on the city. To be more prepared, they take part in practice runs like Exercise Ruaumoko. Accurate risk assessment is only possible when a large group of people get together to make sense of various bits of information.

Research by DEVORA in 2025 found that base surges (phreatomagmatic activity) could potentially travel up to 5–15 km away from the vent. This information led the Auckland Emergency Management to update their response plan – previously it was thought it could only reach up to a 5 km radius.