Auckland: Where unknown volcanoes lie beneath the surface

View on CBD from Auckland Domain. Photo / Getty Images

Who would have thought the newest volcano in the Auckland region would be found after a man lodged an application to build his dream home on the land?

In July Wayne Valder, who owns property in Karaka, was planning on building a five-bedroom house on the land.

There had always been whispers of a volcano hidden in plain sight near Karaka, but last year the rumour was confirmed as fact.

So some locals decided to write to the University of Auckland and Waikato University asking them to investigate.

Auckland Council got involved and eventually contracted a geologist and volcano expert to take a closer look.

Bruce Hayward, who has written a number of books on Auckland's volcanoes, initially disregarded any chance of an unknown volcano existing in Karaka.

However, the geologist and volcanic expert decided to use LiDAR scanning in the area and discovered an old and degraded castle and moat volcano.

Karaka volcano. Photo / Bruce Hayward

A castle and moat volcano is one which has a large explosion crater with a raised tuff ring around it and a small scoria-rock cone nestled inside.

Hayward explained the cone is the castle and the circular crater depression around it is the moat.

After some more investigating, he concluded there was a basalt volcano mantled by thick weather volcanic ash at the site.

Hayward said he was "absolutely staggered" when speaking to the Herald last year."All geologists knew there was no volcano near Karaka, which was outside the known limits of the Auckland and South Auckland volcanic fields," he said.

"How wrong we were."

A map of the South Auckland Volcano Field. Photo / Bruce Hayward

There are 53 recognised volcanic cones in the Auckland Volcanic Field, all of which have erupted in the past 200,000 years.

However, the new volcano found near Karaka is not part of the Auckland Volcanic Field. Instead, it's found in the South Auckland Volcanic Field.

Hayward said the South Auckland Volcanic Field is very similar to the Auckland one and it extends between Karaka and Papakura to Pukekawa and to Waiuku.

The South Auckland Volcanic field features at least 85 recognised volcanoes which erupted between 1.5 million and 500,000 years ago.

Hayward also said there are also similar young volcanic fields around the Whangarei and Kaikohe-Kerikeri area in Northland.

"The other major volcano near Auckland is the extinct Waitakere volcano which was the largest cone volcano in New Zealand with a footprint 60km by 40km across and an estimated height of 3000-4000 metres above the sea floor," he said.

A map of the Auckland Volcano Field. Photo / Bruce Hayward

"It was intermittently active between 22 and 15 million years ago.

"Today most of it has been eroded away by the Tasman Sea and only the uplifted submarine eastern slopes survive as the Waitakere Ranges."

The oldest volcano in the Auckland Volcanic Field is Pupuke, which erupted around 190,000 years ago.

The ages of the volcanoes are at times of eruption, essentially each volcano only erupted once over a period of a month to a few years.

It is unlikely another volcano would be found in the Karaka or even South Auckland Volcanic Field, Hayward said, but it's possible.

"No extra volcanoes were recognised in the Auckland Volcanic Field between 1960 and 2010 - 50 years," he said.

"I would be surprised if another volcano is not recognised in the South Auckland Field in the next decade or so, but it is unlikely to be as large or as obvious as Karaka.

Bruce Hayward warns the small volcanic cone is about to be destroyed and buried under a housing development. Photo / File

"We have examined the LiDAR and other information within 5km of the Karaka volcano and cannot find good evidence of others nearby in this area."

The Herald was unable to contact Wayne Valder, the man who hopes to build his dream home on the property. Here are some of Auckland's more well-known volcanoes from around the city which you can visit:

Rangitoto Island

Rangitoto. Photo / Bruce Hayward

Eruption: 600 years ago.

Rangitoto is Auckland's most iconic volcano. It's a low and long island cone and is located off the coast in the Hauraki Gulf.

It's the city's youngest volcanic cone at around 600-years-old but is also the region's biggest.

It is home to a variety of plant life and is thought to be especially significant as an example of ecological succession.

The island begins with the bare ground of raw lava fields which eventually become established forest.

A short 30-minute trip by ferry, Rangitoto is also home to walking and hiking trails and features a boardwalk to the summit.

Mt Eden (Maungawhau)

Mount Eden. Photo / Bruce Hayward

Eruption: 28,000 years ago.

Standing just shy of 200m high, Mt Eden boasts itself as Auckland's highest mainland volcano at 196m.

It features three main craters in a row, creating an oval shape covered by green parkland.

The volcano formed 20,000 to 30,000 years ago and is a former Māori settlement.

In 2014, a collective settlement was reached between 13 iwi over the 14 maunga, so all 13 tribes hold guardianship over the volcano.

Its ancient lava flows covered 5.6sq km and contained enough lava to fill roughly 32,000 Olympic swimming pools.

One Tree Hill (Maungakiekie)

One Tree Hill. Photo / Bruce Hayward

Eruption: 60,000 years ago.

The founding father of Auckland city, Sir John Logan Campbell, is buried at the summit of One Tree Hill. One Tree Hill was also a former Māori settlement and has more than 170 constructed terraces based around three Māori pā.

The volcano is the largest prehistoric earthworks fortifications worldwide and is currently filled with walking tracks, picnic areas, and paddocks filled with farm animals.

Mt Victoria and North Head (Takarunga and Maungauika)

Mount Victoria. Photo / Bruce Hayward

North Head. Photo / Bruce Hayward

Eruption: 35,000 years ago & 90,000 years ago.

Mt Victoria and North Head sit side by side in Devonport, surrounded by the Hauraki Gulf and look out towards Rangitoto Island.

Formed over 50,000 years ago, North Head is another one of Auckland's oldest volcanic cones.

Both volcanoes are the sites of former Māori pā and also have previously housed military installations.

Mangere Mountain (Te Pane o Mataoho)

Mangere Mountain. Photo / Bruce Hayward

Eruption: 50,000 years ago.

Mangere Mountain, or Te Pane o Mataoho, is Auckland's best-preserved volcanic cone and looks out across the Manukau Harbour.

The volcano sits at 106m above sea level and remains of former Māori settlements are nestled throughout it.

It first erupted around 70,000 years ago and lava fields spread out in all directions except the southeast.

The volcanic activity which first formed the 'mountain has died away but evidence of its eruption and formation surrounds it.

Auckland Domain

View on CBD from Auckland Domain. Photo / Getty Images

Eruption: 100,000 years ago, approx.

Pukekawa, the Auckland Domain, is one of the city's oldest volcanoes and erupted over 100,000 years ago.

The volcano is the city's oldest park and is the home of the Auckland Museum.

The museum sits on the edge of Pukekawa's explosion crater which is now filled with sports fields and the gardens of the Domain.