Tuesday, 3 May 2022

Guest post by Chris Twemlow and Karoly Nemeth. The ghosts of old volcanoes in Coromandel.


Karoly Nemeth is Professor of Geology at Massey University in Palmerston North, and Chris Twemlow is Kauri Dieback Ranger for the Department of Conservation, Whitianga District. Recently we spent a weekend exploring some spectacular geological sites on the Coromandel Peninsula, as background research to a recently published paper exploring the geodiversity and geoconservation values of this area. To take a  journey through this geologically and culturally rich area read on.......

 

Chris Twemlow and Karoly Nemeth get up close to an outcrop of the Tahanga Basalt
on the Kuaotunu Peninsula, Coromandel. Source: Gravis (2020).


Map of the central North Island of New Zealand
showing Kuaotunu on the eastern coast of the Coromandel
Peninsula. Source: Backpack New Zealand (2020).


Geological map of the Kuaotunu Peninsula showing the main geological formations and rock types in the area. Source: Karoly Nemeth (2020).

 

Our own Giant's Causeway.....

Columnar jointed basalt forms as the lava cools more quickly at the surface than in the interior of the lava mass. This in turn builds up stress and this stress is dissipated through the formation of cracks running branching at 120 degrees. One of the most famous examples is The Giant's Causeway in northeastern Ireland. These formations can also be found in New Zealand, with one of the most spectacular examples forming Motutu Point, between Whangapoua Beach and Wainuiototo Bay (New Chums). This headland shows striking examples of columnar basalt, with the remains of a Māori Pā seen on the grassed slope above the columns. Another example of columnar basalt can also be seen at Mt. Cargill in Dunedin, and are known as "The Organ Pipes" due to their columnar shape.

Above and below: Basalt columns are clearly visible from New Chums Beach,
where the grassy top of Motutu Point is also visible, the site of a Pā site.
Source: Gravis (2020).




Source: Karoly Nemeth  (2020).



Above: Over time basalt columns erode and collapse leaving the foreshore
littered with boulders, while the relentless action of salt water and waves
produces distinctive features. Source: Gravis (2020)

Tahanga Basalt.

Basalt in the Coromandel  generally occurs as the Mercury Basalts, erupted 5 -8 MYA. As well as forming the columns at Motutu Point, on the Kuaotunu Peninsula the Mercury Basalt forms Mt Tahanga, and can be seen outcropping on the beach. Mt. Tahanga is a highly significant maunga, as this was the source of a particularly fine-grained basalt highly prized for tool making and widely traded throughout New Zealand prior to European settlement. The maunga is the site of several pre-European quarries, and examples of the fine grained-basalt can also be found on the beach.


Above: Rubbly outcrops of Tahanga Basalt can be seen on the foreshore below Mt. Tahanga,
with flow features visible in the eroded basalt of the shore platform. Significant
pre-European quarries where this highly prized basalt was worked are situated
further up the slopes of Mt. Tahanga. Source: Gravis (2020).



 
Above and Below: This detail shows three samples of Mercury Basalts all found within
a one kilometre area. The sample on the left shows a coarse grain with clearly
visible feldspars, while the sample on the right shows the very fine grained and dense
Tahanga Basalt, with no crystals visible to the naked eye. Source: Gravis (2020).


 

Kuaotunu Peninsula

This peninsula sits on the eastern coast of the  Coromandel Peninsula and north of  Mercury  Bay. It is a geologically diverse and culturally rich area, with a dynamic history of human settlement from the earliest human arrivals in the country to the period of the Coromandel gold rush and beyond. 


 

One of the highest points on the peninsula is Blackjack's Hill, which looks out towards the Mercury Islands, and to Opito Point at the end of the peninsula. Blackjack's Hill is the site of a long extinct geothermal field with signs of well preserved quartz and geothermal deposits to be found around the tracks. The details below show example of quartz-based rocks and minerals that can be found inland, and also on beaches and in rivers in the area.






Otama Dunes and Wetland.

Otama Beach forms part of the north-facing coast of the Kuaotunu Peninsula, and is significant as one of the most undisturbed beaches and associated sand-dune formations in the Coromandel. The distinctive white sands are high in quartz and silica, while active dune formations with a back-dune wetland annd associated ecology are increasingly rare. Nearby Sarah's Gully is the site of one of the earliest sites of Māori settlement in the area, with archaeological evidence in the area showing the eastern coast of the Coromandel was a thriving area of settlement up until the arrival of the first Europeans. 

Source: Davidson (2018). In search of the North Island Archaic:
Archaeological excavations at Sarah’s Gully, Coromandel Peninsula,
New Zealand, from 1956 to 1960. Tuhinga 29: 90–164

 

In more recent times, this area has become the focus of a significant restoration project by the Otama Reserves Group.


Above and below: Distinctive dunes are formed by pale coloured
quartz-rich sands, formed by the weathering of silica-rich volcanic
materials. Source: Gravis (2020).


 

Above: This area is well known for its sparkling white sand beaches. This detail
shows the high content of quartz fragments, formed by physical weathering
of silicic volcanic materials. Other volcanoc products less resistant
to erosion have been broken down by chemical weathering. Source: Gravis (2020).

Above and below: The dunes harbour a diversity of
rare and unusual vegetation adapted to life in this
sandy and harsh coastal environment.
Source: Chris Twemlow -  Otama.org.nz (2020)







Trees surrounding the estuary behind
the dunes provide a haven for nesting shags
Source: Gravis (2020).

New Chums Beach. 

Wainuiototo, more commonly known by the name New Chum Beach, is justifiably well known for its unspoilt sands and specatcular coastal outlook. Less well-known are spectacular outcrops of volcanic breccia originating from one of the main eruption centres in this area.  Brightly coloured scoria and andesitic pebbles and boulders are preserved in a matrix of ash and tephra, with weathering leaving fresh surfaces well exposed.

 

Above: Coastal erosion processes continuously expose
fresh surfaces, allowing a view into the volcanic
features formed during unfolding eruptive processes.
Source: Gravis (2020).


Above and below: A range of bright colours
and rock types suggest a dynamic and rapidly
evolving volcanic environment shaped by magma
chemistry, environmental conditions, and physical
parameters. Source: Gravis (2020).



Above: Erosion exposes the inner workings of a
volcano, with a dyke and layers of ash and volcanic
debris visible here. Source:Karoly Nemeth (2020).


 

Coromandel Granite.

This distinctive igneous rock is well known as "Coromandel Granite", though strictly speaking it is more correctly defined as a tonolite due to its mineral composition. Granitic type igneous rocks form when magma does not erupt to the surface as lava, but slowly cools underground. This slow cooling, which may take thousands to millions of years, allow the large crystals to form which are so clearly visible in these types of rocks. Over time uplift and surface erosion expose the granite body (or pluton) where we find it at the present-day surface.

The Coromandel Granite is significant because it is a very rare outcrop of plutonic rock in the North Island, with most granites found at the surface in New Zealand in the South Island. For a time it was quarried and used as a building stone, including in the Old Parliament buildings in Wellington. 

This fascinating area tells a story of volcanic processes taking place deep underground millions of years ago.It is also significant as a site of a considerable stone extraction industry, utilising a locally unique stone resource with relative ease of access and proximity to local shipping routes. However, over time the extraction and supply became uneconomic, especially in the context of an increasingly globalised stone supply industry. 

Above: The stone quarry is an hour north of Coromandel
Township, a relatively remote location on the coast via road.
At it's height of production coastal shipping provided
convenient transport between the peninsula and Auckland,
making this a well-placed location for the times as seen in
this aerial phot of the coast from 1945. Source:Retrolens.nz (2020).


Above: This zoomed detail from the image above clearly
shows the stone wharf, and nearby houses for quarry
workers. To the left can be seen a distinctive tidal
shore platform formed by the hard erosion resistant
igneous rock. Source: retrolens.nz (2020).


 


 
Above: The structure of the wharf formed by blocks
of this very hard igneous rock remain clearly
visible here. Source: Gravis (2020).



Above and below: The large crystals forming
this granitic rock are clearly visible to the naked eye.
Also cleary visible on blocks and boulders in the area
are drill holes where drills were used to break up the rock
into blocks for shipping. Source: Gravis (2020).



Above and below: Near the site of the old quarry
on the beachfront can be found a type of rock called
hornfels. This forms when surrounding rock is "baked"
and undergoes structural and chemical changes due to the
heat of the intruding magma body. Source: Gravis (2020).

 

Above: Parliament buildings in Wellington, showing steps and
the bases of columns made of Coromandel Granite and facings and
colums made of Tākaka Marble. Source: Te Ara - The Encycopedia of
New Zealand (2020) Photograph by Alastair McLean.


 

Acknowledgements 

 

Above: Inspiration for focusing on this area of the
North Island principally came from the book "Vanishing
Volcanoes" by Philip Moore and Homer Loyd, unfortunately
now out of print. However, our ongoing research aims to
build on this valuable work both in this region and other
areas of the country.

Above: Follow this link to a full copy of The Ghosts of Old
Volcanoes, A geoheritage trail concept for Eastern Coromandel
Peninsula, New Zealand.



"Out of the Ocean, Into the Fire" by Bruce Hayward provides
a good overview of the geological history of the Coromandel
in the context of the upper North Island.



 

Sunday, 10 October 2021

Guest post by Lisa West. The visitations of Randolph Kākā.

Lisa West is a jeweller, sculptor, and writer based in the bush-clad harbourside oasis of Birkenhead, in Auckland New Zealand. From her studio she keeps an eye on regular feathered visitors to the bush, including a now-regular visitor, Randolph the kākā. To read more about Randolph and his kākā friends,   read on..... 

The first time we saw the kākā was in late Autumn of 2020. It was just on dusk post lock-down and we were wending our way down our driveway after visiting our local night market. He was a high dark mark on the sky above us, distinguishable only by his joyous prehistoric skraarking. We jumped up and down screaming with sympathetic delight, because that is the effect kākā have when you realise they are in your suburban Auckland neighbourhood.

Lisa West's Auckland studio looks out onto native bush, the perfect spot for viewing
native bird antics, and finding inspiration for her jewellery, like this button inspired by Randolph the kākā. Source: Lisa West Jewellery (2021).

 

Kākā have been spreading out across the Auckland isthmus for a few years now, charming, charismatic winter visitors to bush-clad suburbs. The Auckland kākā belong to a flock originating  from Hauturu Little Barrier Island in the Hauraki Gulf, who after breeding migrate further afield to forage before returning to their island haunts in early spring to breed. It was a few weeks until he finally arrived in our backyard, a flurry of tui in his wake. He sat in the kanuka alongside our deck, fluting and cackling, and I rang my Dad, and held the phone out towards the tree so he could hear. I was gabbling with excitement. 

 

Above and below: Randolph the kākā at home in the Birkenhead bush.
Source: Lisa West (2021).

 

One morning when I was lounging in bed I saw him land on the deck outside the window to investigate some apple left out for the waxeyes. I watched him delicately grasp a piece of fruit with  his zygodactyl foot. He discarded it as beneath his dignity; apparently kākā have the exalted tastebuds of Roman emperors and only a platter of persimmons and peeled grapes will suffice for these patrician parrots. There are no luxury fruits available in the bush gully behind our house though; I think the kākā are attracted by the tall old-growth kanuka and tanekaha that provide an outlook, as well as sap to suck, and grubs to winkle. Kākā are adept at bark stripping kanuka in order to fossick out food.

Feeding kākā showing it's veratile beak and claws.
Source: Wayne Smith (2021) waynephotosmith @ instagram

The first time we had a truly close-up encounter with the kākā we had christened Randolph was when he suddenly landed in the tree outside my workshop and insouciantly climbed down using his leatherman beak and feet as grappling hooks before positioning himself on a slim branch perch to investigate the tui feeder. An agitation of swirling tui whirred and clicked in dismay as Randolph grabbed their drink container and gently tilted it, releasing a steady stream of liquid, much to their consternation.

 
We immediately observed that Randolph was a handsome bird, khaki/brown, a silver fox slick-down of whitish-grey feathers atop his head, a blush of copper on his cheeks, a flourish of brass behind his dark eyes, and a huge hooked slate-coloured beak. His impressive scaly talons grasped the branch and the container, and we had a brief flash of his red pantaloons. We don’t actually know if Randolph is a male or a female, because we haven’t seen him side by side with another kākā of a different sex. There is some sexual dimorphism in kākā, the females are slightly smaller, and the males heads and upper beaks are considerably larger.

Clear view of distinctive facial colouring and reg underparts on kākā.
Source: Wayne Smith (2021) waynephotosmith @ instagram

 

Kaka are ‘deep endemics’ from the family Strigopoidea, an ancient group that split off from all other parrots millions of years ago. Kākā belong to the genus Nestor, along with the kea, and two extinct kākā, the Chatham Island kākā, and the Norfolk Island kākā. They have a close relative in the kakapo. I keep reading that kākā and kea species are claimed to be ‘primitive’ on the basis of their early departure from other parrot species, but really it means they are the most basal clade of parrots, taxonomically speaking.  In simple terms this means because of the break up of Gondwanaland, they are a direct descendant of a proto-parrot, without the variety of divergence you see occurring in other parrot species. They are more distinct from all the other parrots than all the other parrots are from each other.

However, because Kākā and their fellow NZ parrots have adapted and specialised to the unique environment of the isolated islands they inhabit over a long time period, they are unlikely to have a close resemblance to their proto-parrot ancestor. That’s enough of the dry science for now though.

I took to keeping a diary of his visits. September was a busy month for backyard kaka sightings. He came almost every day, the earliest visit at 3.09 am, on Sept. 21, when he fluted intermittently through the early hours of the morning.
 

As I sleep lightly, I was able to keep track of when I heard his alarm clock fluting. A diary entry from Tuesday Sept. 15 reads: 

5.58am- a joyous cackling skraak, & light fluting to the South
6.08am- considerable fluting

5.30pm-ish- skraaks
 

Other diary entries describe: ‘Exuberant clowning in the canopy’, and yet another says:

‘Yesterday he flew past the ranch slider at low altitude - let loose a loud startling skraak which caused screams of fright - 1pm.’
Saturday Sept. 19 says:

5.46am- a flurry of cackling skraaks to the south followed by querulous fluting. #skraakflutetseep.
 

There is a little ballpoint pen sketch of a kaka head adorning the page.
 


I developed a vocabulary of kākā sounds; skraaking, fluting (light, diminishing, or querulous), tseep-tseeping, cackle-hissing, gurgle-growling, gurgle-cackling, snarl-skraaking, and the curious WEE-do, which is almost an electronic noise. I recorded his chatter obsessively, and made videos of his visits. Randolph was unperturbed by the distraction he caused, and not alarmed by our interest in him. One exciting day Randolph had a friend fly in for a chatter. I have a recording of this event in which we are heard to exclaim excitedly “There’s two of them, TWO of them!”

 

A diary entry on Wednesday Sept. 23 states: 

8.30am- a kākā flew South past the bedroom window followed immediately by two large kākā who flew from the South & then wheeled down into the gully. No skraaking- a couple of light flutes.

 

We worry about humans imprinting on wild animals, but I think the urban kākā imprint on humans.

Evidence of kākā imprinting on human behaviour
Source: Lisa West (2021).
 

Often Randolph’s visits were heralded by a pertubation of tui. I would glance out my workshop window and see an agitation formenting in the tall trees outside, tui blasting in from all directions and positioning themselves like spectators in a Roman amphitheatre. More often than not he would blithely ignore them, as he perched quietly high in a tree, calmly ring-barking small branches, his presence betrayed by seeds and bits of bark dropping to the ground from his ministrations. If he hopped down to investigate the tui feeder he was rewarded by messerschmitt attacks as tui took turns to swoop at him, executing last moment swerves. When that became tiresome he would suddenly turn tail and freewheel down the gully flashing his brilliant red underthings, and skraaaking with mirth.

Kākā in flight through NZ bush.
Source: Wayne Smith (2021) waynephotosmith @ instagram

 

Kākā are omnivorous birds, with a diet consisting of fruit, berries, flowers, nuts, seeds, nectar, and small invertebrates and their larvae. They have long slender upper beaks for tearing bark, as well as brush-tipped tongues for sap-licking and nectar extraction. Their zygodactyl feet, meaning two toes forward and two toes backward, also give them the advantage of the equivalent of two opposable thumbs on each foot which are the perfect tools for grasping and climbing.The combination of being a powerful flier and having a varied diet is that kaka can forage afar as various foods come into season. We note that Randolph disappears as soon as the kowhai start blooming in early Spring, and I start to see posts appearing on social media of kākā enjoying the yellow blossoms all over Auckland.

Kākā feeding on nectar rich flowers of the native kowhai tree.
Source: Wayne Smith (2021) waynephotosmith @ instagram


On one occasion a tui thwocked into my workshop window, a very uncommon occurrence, as they are accomplished fliers, whirring and gliding over and around the house frequently. He had knocked himself out cold, so I called Simon down to tend to him. As Simon bent over the tui, Randolph plonked suddenly down onto the branch above Simon’s head, curiously craning to see what was going on. I dislike anthropomorphising, but I had observed what appeared to be a reasonably good-natured chase going on earlier, tui beak to kākā butt and vice versa tearing at speed past the house, and wondered if the tui was an inadvertent victim of the game. The tui was fine after a few minutes quiet time in a cardboard box, and I doubt parrots feel much remorse. It’s all fun and games till someone smashes into a window pane.

From Sunday Sept. 27 there are no kaka sightings recorded in my diary, just an sad little entry that says:

'The long silence :(  Have the kaka returned to Little Barrier?
 

They returned for a brief visit in early October, but breeding season was in full swing on their Hauraki Gulf island strongholds, so we had no expectation of seeing them till winter of 2021.

Kākā have very specific requirements with regard to a suitable breeding nest. They prefer cavities in large old forest trees, at least 5 metres above the ground which they line with woodchips. The female lays a clutch of about four eggs which she incubates solely, and the male kākā brings her food.

Kākā evolved and adapted in an environment without mammalian predators, and under those conditions, being a cavity nesting Nestor was a good solution. Unfortunately the introduction of predator species has been disastrous. The worst indicators for kākā success are stoats and possums.

From the time the eggs are laid till the time the chicks can fly is three to four months, which is a very long time for the female kākā to be vulnerable to predation. The high ratio of male birds to female birds is stark evidence that predator control is essential for kākā to flourish. Likewise, fledglings often fledge before they can fly or climb, so spend some time on the forest floor before being able to find safety in the treetops. This makes predator control of cats, stoats, and rats vital to ensure their survival.

Predator control has been proven to work in favour of kākā. The Pureora Forest Park in central North Island is a case in point; a fourfold increase in kaka in 20 years, from 640 in 2000 to 2600 in 2020. Even more exciting is that the ratio of female to male is approaching 1:1, as opposed to 1:2.1 previously!

Kākā are still regarded as under threat though. If kākā are visiting in your neighbourhood, or a suburb nearby, the most efficacious things you can do to encourage them and make their environment safe is to trap assiduously for rats, mustelids, and possums, and plant the native trees they love for food and habitat. Most areas in New Zealand have volunteer groups that trap, weed, and plant. Every effort helps, no matter how small it may seem.

Randolph and friends reappeared this year, earlier than last year, but they also departed earlier. I haven’t heard or seen a kākā since September 20 when Randolph dropped in for a raucous chat.  I’m hoping they appear for one final visit, but if not, I’m confident of their return in winter of 2022.

You can become Randolph's friend on fb here, and vote for kākā for Bird of the Year 2021 here. A huge thanks to Lisa West, campaign manager for Kākā BOTY 2021 and to Wayne Smith for sharing his great photographs.

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