environment

Auckland lava caves worth protecting

It may be hard to protect something you can't see, but lovers of Auckland's lava caves argue they need legal protections before more are destroyed, as Paul Charman writes.

It’s not just Aucklanders who value the wonderful structures beneath their city, called lava caves.

They’re widely celebrated as something very special, occurring in volcanic fields right across this planet as well as on others.

Lava caves are unique for being formed in a mere blink of geological time (days or weeks), as cooling lava flows across planetary surfaces following volcanic eruptions.

This in such contrast to the more common limestone caves, which are scoured out over the eons by acidic water, and it means that lava cave structures may be completely secretive, points out lava cave speleologist Peter Crossley.

“Unlike the limestone variety, which will generally have a river or stream washing in at one end and out at the other, these caves are just spaces underground which lava has drained out of,” Crossley says.

As a field of many low volcanoes, Auckland is this country’s main habitat for them, though they are generally only discovered when a roof falls in - or in more recent years, when disturbed by construction.

Crossley has been caving since 1965, making a special study of the 500- to 500,000-year old caves found beneath Auckland streets and parks.

From graves to rubbish holes

He has wriggled, scrambled and walked through every lava cave discovered at Auckland in recent years, checking the state of preservation at about 250 sites.

Most are in private hands so are not readily visited. Some have been covered over by buildings and roads, or filled in because they were not understood to have Māori heritage or scientific value.

Some fortunately are on public lands such as Rangitoto and can readily visited, with a good torch.

Pre-European Māori used shallower lava caves for burial, but more recently they have been used as rubbish holes, or back-filled ahead of development.

Even though there are provisions in the council regulations requiring notification if they are found during excavations, this does not always happen, as Crossley has seen from underneath when coming across fill from a building site.

"How do you foster stewardship for a landscape that most people don't believe in, let alone can't see?"

“Some developers do the right thing and the outcome is a win for all, as the caves have been preserved and entry has been facilitated for the future along with detailed mapping under surrounding properties,” he says.

Over the last couple of years artist Chirag Jindal has been working with Crossley to map the caves using 3D terrestrial LiDAR. His project, titled "Ngā Mahi Rarowhenua/Into the Underworld", centres around bringing the hidden landscape into the public forum, through a series of stunningly beautiful lightbox images that were exhibited as part of a large-scale public exhibition last September.

"Unlike our maunga, these caves are unseen, and inaccessible to the wider public,” says Jindal.

 “Often they are rumoured about as myth and legend, and have been the subject for a lot of fiction - think Maurice Gee. How do you foster stewardship for a landscape that most people don't believe in, let alone can't see? That's what the Into the Underworld project was about."

Lunar lava tunnels can be spotted from Earth - could they become our best hope for survival on another planet? Photo: Supplied.

But lava caves evident on Moon and Mars offer something else again – possibly enabling the future survival of the human species, says American adventurer Michael Chalmer Dunn.

Dunn, who researches lava caves for use as future space habitats, considers them to be the best hope of future interplanetary colonisers wishing to avoid surfaces ravaged by cosmic radiation.

The Cambridge-educated scientist and explorer’s exploits include once leading Sir Edmund Hillary, his son Peter and the first man on the moon, Neil Armstrong, on an expedition to the North Pole.

He has vast experience creating underwater research bases and is an expert in Mars habitation logistics. Dunn says living below the surface of the Red Planet in lava tubes – either pressurised, or containing an inflatable liner – will provide the only feasible environment for ongoing human life there, as opposed to brief visits.

And that means testing the life support systems required (air, water, agronomy etc) within similar structures, first here on Earth and then the Moon, ahead of use on the Red Planet itself.

This reporter is biased on the subject of lava caves, having fallen in love with them many years ago.

While working many years ago as a reporter in Rotorua’s sister city of Klamath Falls, Oregon, I got to explore one of the most famous locations for these structures, the Lava Beds National Monument.

A lava cave in California. Photo: Wikipedia.

This is a high desert area just across the California border from Klamath Falls, and this week's 50th anniversary of the Apollo 11 Moon landing (on July 20) is focusing media attention on lunar exploration research underway there.

Back in the early 1980s, the National Monument provided me and my travelling companion with an exciting introduction to those dry rough-walled caverns, which are so unlike the wet dripping limestone variety one encounters at Waitomo.

Armed with helmets and head lamps, my buddy and I plumbed a system of six tubes, each one running several metres below the previous one, though following almost exactly the same course and direction.

We got to visit these wonders in a clandestine way, as a couple of official cavers, apparently with permission from the authorities, had unlocked their chained-up entranceway. We heard far-off voices but didn’t set eyes upon these bona fide cavers.

It was cheeky to take advantage of this situation but provided a wonderful adventure – which even included encountering a swarm of sleeping bats – and it left me with a lifelong appreciation of the romance of lava caves.

And I am not alone in getting a wee bit tetchy when these structures are needlessly destroyed.

Auckland cave falls foul to development

Thanks to reporting by the NZ Herald’s property editor Anne Gibson, we have learned of the likely destruction of quite a large cave system, albeit years after the event, as those involved in the construction feel now apparently free to disclose what they know.

Apparently, Auckland Trotting Club’s 246-unit Alexandra Park project in Greenlane fell afoul of these geological wonders, whose presence had not been picked up by test bores, helping to send its building project into the red.

Sources quoted in the story suggested that the discovering of these voids – some up to four metres wide – were not reported as stipulated by Auckland Council protocols.

Instead hundreds of cubic metres of costly concrete and grout were used to fill the spaces.

Karma or not, it seems a tough outcome for the Trotting Club, whose project won’t now clear costs, necessitating the sale of additional land, and the controversy created is still gathering steam.

The Alexandra Park example was referenced on RNZ on July 10 in the context of how we prevent priceless geological taonga falling prey to the diggers.

Dr Bruce Hayward from the Geoscience Society told Nine to Noon presenter Kathryn Ryan that the Alexandra Park case showed developers still quietly get away with destroying valuable geological sites.

University students search for fossils at Foulden Maar. Photo: Larusnz CC BY-SA 4.0

He said the case of Foulden Maar fossil bed, near Middlemarch in Otago, was a classic example of this.

The 28-million-year-old site with perfectly preserved fossils has somehow flown under the radar of national significance, said Hayward, to the extent that the minerals there is are now likely to be mined for use as an additive for pet food production.

“The problem will certainly happen again somewhere in New Zealand unless action is taken."

He wants fossil beds, lava caves and other outstanding geological features, which are already in the Resource Management Act, to be clearly defined, documented and assessed as a matter of national importance.

Amanda de Jong, the team manager for compliance monitoring at Auckland Council, says several known lava caves are listed as Outstanding Natural Features in the Auckland Unitary Plan and therefore have protection.

As well as protection for known caves, there are also rules for the accidental discovery of them.

These rules were established during development of the Auckland Unitary Plan and are listed in chapters E11 and E12.

“Should a lava cave be discovered on a site, in the first instance work must stop and council must be informed,” says de Jong.

”Any additional requirements will be advised by council following a site visit to assess the nature of the discovery.”

The council is now working with developers to find out “what may have been discovered” during the construction of apartments at Alexandra Park.

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