Auckland’s 53 volcanoes in order, a 193,000 year map

Auckland sits on a field of 53 small volcanoes. None of them will erupt again, but the field will. This map plays the whole story in order, from the first blast at Takapuna about 193,000 years ago to Rangitoto in the 1400s, using the eruption ages worked out by the DEVORA research programme. Each volcano flares at its vent, then the real tuff, scoria and lava it left behind fill in on the map and cool from orange to the colour of its age.

How to use the map

Press play and the clock runs from 193,000 years ago to today in about two minutes. The bottom axis is not evenly spaced. The last 60,000 years get most of the width because that is when most of the eruptions happened, and the flare-up between about 35,000 and 28,000 years ago and the long quiet before Rangitoto are shaded so you can see them coming. Drag the playhead to scrub, use the speed buttons to hurry the early millennia along, or skip straight to today.

Click a volcano on the map, or a line in the eruption log, to open its card. The card gives the preferred age with its error, how that age was measured, how reliable geologists rate it, the summit height, the area of each deposit type on the geology map, and a short note on what is there now. Hover a vent for a quick label. The zoom controls take you down to street level, where the satellite image shows the craters and cones as they are today.

What the colours mean

Every volcano is coloured by its age. Deep violet is the oldest, from Pupuke at 193,000 years, through magenta and red in the middle of the record, to the orange of Mount Wellington at 10,000 years and the yellow of Rangitoto. When a volcano erupts on the map it glows hot orange for a moment and its deposits spread outward from the vent, then it settles to its age colour. Lava is drawn solid, scoria cones are drawn slightly paler on top, tuff rings are translucent and ash blankets are fainter still. Two craters that have never been dated, Cemetery Crater and the Puhinui Craters, are shown in grey from the start.

The order of Auckland’s volcanoes

The table lists all 53 centres in the order used on the map, oldest first. Ages are in years before present with the two standard deviation error where one is published. The reliability grade follows the grouping used by Hopkins and colleagues in their 2021 review, from high for reproduced, reliable ages down to undated. Where a volcano has both a Māori and an English name, both are given.

Where the ages come from

The ages are the preferred ages published in Auckland Volcanic Field magmatism, volcanism, and hazard: a review by Jenni Hopkins and colleagues in the New Zealand Journal of Geology and Geophysics in 2021, the summary paper of the DEVORA (Determining Volcanic Risk in Auckland) programme. That table reconciles every published date for the field and rates each one. It draws on two big pieces of work. Graham Leonard and colleagues at GNS Science, working with the US Geological Survey, used high-precision argon-argon dating of basalt to date many of the cones directly. Hopkins used the chemistry of ash layers recovered from cores drilled into the maar lakes to match each ash to its source volcano, which placed centres in order even where no rock could be dated.

Before that work only 12 of the 53 centres had reliable ages. Now 47 do. The remaining six have either a minimum age, for example Boggust Park Crater and Pukewairiki must be older than 130,000 years because the sea eroded them during the last interglacial, or no age at all. Several small centres whose deposits lie directly on a neighbour’s, with no soil between, are placed 500 years after that neighbour by convention. Rangitoto’s two eruptions are radiocarbon dated by Needham and colleagues to about 553 and 504 years before 1950, which is roughly 1400 and 1450 CE.

Two things to keep in mind when reading the order. First, the error bars overlap for many of the volcanoes in the flare-up, so the sequence within that cluster is not certain. Second, ages rated uncertain, such as Mount Victoria, Mount Hobson and Mount Cambria, could move a long way when they are re-dated. The map follows the preferred age in each case.

How the footprints were drawn

The shapes on the map are the volcanic units of the GNS Science 1:50,000 geological map of the Auckland urban area, published as the Kermode 1992 sheet and updated in 2001, taken from the GNS web feature service. The map separates lava, scoria, lithic tuff, and ash and lapilli, including lava now below sea level, but it does not record which volcano each polygon came from. We assigned every polygon to a vent. A polygon that sits on a vent belongs to it. A polygon touching several vents is divided between them by distance, with big cones given a little more reach, and three flow fields that are well documented, One Tree Hill’s flows to Onehunga and Three Kings’ flow to Western Springs and Meola Reef, were set by hand.

That makes the footprints an honest approximation rather than a per-volcano geological map. Where flows from neighbouring cones merged, for instance around Mount Smart and One Tree Hill or across the Mount Eden and Three Kings fields, the boundary between them is our estimate. Rangitoto’s footprint includes lava the map shows below sea level, which is why it is larger than the island. Two craters recognised only in 2011, Boggust Park and Cemetery Crater, do not appear on the 1992 map at all, so they are shown as a dashed ring at their location. The card for each volcano gives the mapped area of each deposit type so you can see what the shape is built from.

What the sequence shows

The record starts slowly. Three explosion craters formed on the North Shore within about 12,000 years of each other, then the field produced only a handful of eruptions over the next 100,000 years. The rate picks up from about 60,000 years ago, and 35 of the 53 centres have erupted since then. Between about 35,000 and 28,000 years ago a dozen volcanoes went off in what the researchers call a flare-up, including Three Kings, Mount Eden and Wiri Mountain. Then came a run of eruptions on the eastern side of the isthmus, then Purchas Hill and Mount Wellington about 10,000 years ago, and then nothing for roughly 9,500 years until Rangitoto.

Rangitoto changed the field’s arithmetic. Kereszturi and colleagues estimated the total magma erupted by the whole field at about 1.7 cubic kilometres of dense rock, and Rangitoto alone accounts for about 0.7 of that, around 41 per cent. The smallest centre, Ash Hill at Wiri, produced 0.000076 cubic kilometres. Most eruptions were small, punctuated by a few big ones.

When is the next eruption?

Nobody can say. GNS Science describes an eruption in the Auckland Volcanic Field as a low probability event on human timescales but one with high consequences, and its own summary of the DEVORA dating work says the field is temperamental, that the past is complex, and that scientists must wait to see what it does next. Averaged over the whole record there has been one eruption every 3,900 years or so, but the field has run hot and cold, with six or more eruptions inside 4,000 years at one point and gaps of up to 10,000 years at others. The next vent will be somewhere new. Each Auckland volcano erupts once.

Because the magma is fluid basalt that rises quickly from 70 to 90 km down, the warning before an eruption is expected to be short, measured in days rather than months. GeoNet runs a seismic network across the city to catch the first signs. Modelling led by Alec Wild at the University of Auckland, published in 2021, found that around 320,000 people might need to evacuate from the zone around a new vent and that the evacuation would take about 49 hours to complete. Auckland Emergency Management’s advice is to have a household plan, as for any other hazard.

Frequently asked questions

How many volcanoes are there in Auckland?

The accepted count is 53 volcanic centres, the figure used by GNS Science, GeoNet and the DEVORA programme. The number has crept up as buried or subtle craters have been recognised, most recently Boggust Park Crater, Cemetery Crater, Pukewairiki and the Puhinui Craters in 2011 and the Grafton volcano in 2010.

Which Auckland volcano is the oldest?

Pupuke, the maar that holds Lake Pupuke at Takapuna, at 193,200 years with an error of about 5,600 years. Onepoto and Tank Farm, also on the North Shore, followed within about 12,000 years.

Which is the youngest?

Rangitoto, which erupted twice, about 1400 and 1450 CE. Before that the youngest was Mount Wellington, about 10,000 years ago, with Purchas Hill just before it.

Will Mount Eden or Rangitoto erupt again?

Almost certainly not. The Auckland field is monogenetic, meaning each vent is fed by a single batch of magma and erupts once. The next eruption will come from a new vent somewhere in the field.

Where will the next Auckland eruption be?

Unknown. The existing vents cluster on the isthmus and in Māngere, but DEVORA’s analysis finds no pattern in the timing or location of past eruptions that would let anyone forecast the next one. The map’s closing view draws the extent of the field so far, and the next vent could be anywhere inside it or a little beyond.

Sources

• Hopkins, J.L., Smid, E.R., Eccles, J.D., Hayes, J.L., Hayward, B.W., McGee, L.E., van Wijk, K., Wilson, T.M., Cronin, S.J., Leonard, G.S., Lindsay, J.M., Németh, K. and Smith, I.E.M. (2021). Auckland Volcanic Field magmatism, volcanism, and hazard: a review. New Zealand Journal of Geology and Geophysics 64(2–3), 213–234. Table 1 is the source of every age, error, method and reliability grade used here.
• Leonard, G.S., Calvert, A.T., Hopkins, J.L., Wilson, C.J.N., Smid, E.R., Lindsay, J.M. and Champion, D.E. (2017). High-precision 40Ar/39Ar dating of Quaternary basalts from Auckland Volcanic Field, New Zealand. Journal of Volcanology and Geothermal Research 343, 60–74.
• GNS Science (2017). Studies reveal Auckland Volcanic Field’s past: it’s temperamental and unpredictable. Joint media release with Victoria University of Wellington, the University of Auckland and Auckland Civil Defence.
• GNS Science. Web Map Service, layer NZL-Urban Auckland geological units, compiled from Kermode (1992) Geology of the Auckland urban area and Edbrooke (2001).
• Kereszturi, G., Németh, K., Cronin, S.J., Agustín-Flores, J., Smith, I.E.M. and Lindsay, J. (2013). A model for calculating eruptive volumes for monogenetic volcanoes. Journal of Volcanology and Geothermal Research 266, 16–33.
• GeoNet. About the Auckland Volcanic Field.
• DEVORA. Scientists examine evacuation timelines for future Auckland volcanic eruptions, on Wild et al. (2021).
• Auckland War Memorial Museum. Not if, but when.
• Hayward, B.W., Kenny, J.A. and Grenfell, H.R. (2011). More volcanoes recognised in Auckland Volcanic Field. Geoscience Society of New Zealand Newsletter 5, 11–16. Vent locations and summit heights checked against the Wikipedia list of the field.

Basemap imagery and labels by Esri and its data partners. Found an error in a date or a name? Tell us in the comments and we will check it against the source.