Scientists say they have discovered at least two previously unknown volcanoes in south Auckland.
Geologist Bruce Hayward says he and colleagues from Geomarine Research have made the discoveries thanks to new, high definition maps of the city.
One cone has been discovered in the suburb of Favona and three have been found at the Puhinui Reserve in Wiri.
Mr Hayward says the cluster of three is likely to be officially recorded as just one volcano because they are so close to one another.
He says the new map technology has allowed scientists to see cones that weren't initially obvious.
"It was only when I started looking at the contour map with those close together contours that suddenly just jump out at you. Up on the top of these hills are these depressions and with a nice circular rim of ash around them," he says.
Mr Hayward says he had walked on the Favona site many times but had never noticed the cone until it became apparent on maps.