What lies BENEATH
Experts ‘knew’ there was no volcano tucked away in Karaka. But they were wrong, writes
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 vacant 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 locals decided to write to University of Auckland and Waikato University asking them to investigate.
Auckland Council eventually contracted a geologist and volcano expert to take a closer look.
Bruce Hayward, who has written books on Auckland’s volcanoes, initially disregarded any chance of an unknown one existing in Karaka. However, the geologist and volcanic expert used LiDAR scanning and located an old and degraded castle and moat volcano. That 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 was the castle and the circular crater depression around it the moat.
After some more investigating, he concluded there was a basalt volcano mantled by thick weather volcanic ash at the site.
“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.”
There are 53 recognised volcanic cones in the Auckland Volcanic Field, all of which have erupted in the last 200,000 years. However, the new volcano found near Karaka was not part of the Auckland Volcanic Field, it was found in the South Auckland Volcanic Field. Hayward said that volcanic field was very similar to the Auckland one and it extended between Karaka and Papakura to Pukekawa and 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 were similar young volcanic fields around the Whangarei and Kaikohe-Kerikeri area.
“The other major volcano near Auckland is the extinct Waitakere volcano which was the largest cone volcano in New Zealand with a footprint 60 km by 40km across and an estimated height of 3000-4000m above the sea floor,” he said. “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 about 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 was unlikely another volcano would be found in the Karaka or even South Auckland Volcanic Field, Hayward said, but it was 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.
“We have examined the LiDAR and other information within five kilometres of Karaka Volcano and cannot find good evidence of others nearby in this area.”
The Herald has been unable to again contact Wayne Valder, the man who hopes to build his dream home on the property.