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.
"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.
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.
