Hidden behind a tropical garden in the affluent Auckland suburb of Mount Eden is a subterranean secret – a cave opening from the ground like the yawning mouth of a giant.
“People come down here and drop their jaws,” says its owner, Sean Jacob, who stands in the centre of the quiet rock chamber.
The cave is 106 metres long and five metres at its highest point. Part way in, the tunnel, which was formed when Mount Eden erupted 28,000 years ago, narrows and then opens into what Jacob calls “the ballroom” – a lofty area shimmering with golden minerals.
Beyond the “ballroom” is a 10-metre crawl space that leads to another chamber. Jacob has attempted to enter it just once. “You draw blood,” he says. “It is like going through a cheese-grater.”
Aucklanders are familiar with the volcanic terrain of their city above ground, living side by side with 53 volcanoes. Yet many are unaware of the extraordinary landscape concealed beneath their feet. Formed by volcanic eruptions, lava caves and tunnels are rare globally, and the sprawling patchwork beneath Auckland is unique to New Zealand. The city sits on top of roughly 200 known caves with a new cave being discovered every month, as construction increases and drilling tools become more sophisticated.
Now, researchers are on a mission to map Auckland’s caves for the first time, in an effort to protect the geological marvels and better understand their cultural significance.
From secret printing press to widow’s shelter
Over the centuries, the caves have been used in all sorts of ways by the residents of Auckland. In 1877, a widow took shelter in a small cave and became known as the hermit of St Anns. In 1940, a group of schoolboys exploring a cave stumbled across a covert communist printing press. More recently, caves have also been used as mushroom farms.
Some residents, like Jacob, have access to their own private caves. Jacob bought a property in 2008 fearing the cave below the house would be destroyed by housing developments if it wasn’t protected.
Since then, he has allowed the public in. It has been used as a film location, an experimental music venue, and visited by a group of school leavers who were blind. He also gets a few unwanted guests including “the occasional person who comes over the fence”.
Auckland’s caves were created over a 200,000 year period – the most recent during Rangitoto Island’s eruption 550 years ago. As lava from volcanic eruptions poured over the land, the outer edges of the lava would cool, forming a dense basalt tube around the liquid rock inside. When the lava inside eventually drained away, it left behind tunnels and caves. Then, over thousands of years, land, rock and plants blanketed the tubes, leaving clusters of caves and tunnels buried below the surface.
Caves have been used as wine cellars, smoko rooms – places for a break from work – storm drainage and rubbish dumps. Others were proposed as possible bomb shelters during the second world war.
Several are hidden under Ambury regional park – a sweep of land fanning out from Māngere mountain, which erupted 70,000 years ago.
Protecting ‘sacred’ caves
Kate Lewis, Auckland council’s geoheritage and natural features expert, dons a yellow hard hat, bunches her shoulders inwards and descends an eight-rung ladder into the ground. The shoulder-width hole would be almost invisible if it were not for a steel grate that typically locks it off from the public, and a perimeter of boulders that stops cattle from treading over it.
Lewis climbs through a mangle of cobwebs and brushes past tiny ferns straining towards the light above. Inside, the cave opens up around her to a knobbly ceiling flocked with moss. About six metres either side, the cave pinches to a close.
“What you see here – these drips,” Lewis says, gesturing to the ceiling, “formed when it was liquid – this whole thing was full of liquid rock, it receded, but the ceiling was still dripping – cool, huh?”
Lewis is part of a growing camp of scientists and enthusiasts who hope to protect the caves.
The history of mana whenua (Māori with territorial rights to an area) relationships to the caves is also “of critical importance” she says – something that has been “completely ignored” and the council is trying to rectify.
For Auckland iwi (Māori tribes), many of the caves are tapu, or sacred, spaces that were used to lay the bones of their ancestors to rest.
Kelvin Tapuke, a senior research fellow at Massey University, says some of the caves are considered a taonga (treasure) to Māori. But since settlers arrived in the early 1800s, they have been disrespected, including the early practice of stealing kōiwi (ancestral human remains) for private collections and international museums.
“It would be like going into where Queen Elizabeth and Prince Philip are buried and raiding their graves,” Tapuke says.
To help achieve better protection, Jaxon Ingold, a masters student at the University of Auckland, is in the process of mapping and creating a complete cave database, through a project called Devora, which is funded by council and the earthquake commission Toka Tū Ake.
Knowledge over the whereabouts of most of Auckland’s caves are held by disparate groups, Ingold says. By collating this information and adding new discoveries as they appear, he hopes to protect the unique geological and cultural history of the caves and ensure future developments can happen safely.
Researchers have to walk a fine line between raising public awareness of the caves, while trying to keep some of their locations private, Ingold says.
“If it is on private property, or mana whenua find it sacred – things like that are more sensitive and may need to be more private.”
Tapuke hopes projects like Ingold’s will build stronger relationships between local authorities, landowners and mana whenua, to generate the respect the caves deserve.
“The caves are sacred,” he says. “They are not a place to tinker around with and people need to respect what they represent – allowing loved ones to rest in peace.”
