<- Volcano city field trip videos
What is the Tāmaki Makaurau Auckland Volcanic Field?
Andrew
Tēnā koutou katoa. Ko Andrew tōku ingoa. Hei kaiārahi ahau ki LEARNZ. Nau mai, haere mai ki Tāmaki Makaurau.
Hey, everybody. I'm Andrew, the LEARNZ educator. And welcome to Auckland. I'd like to introduce you to Thomas, and he's one of a number of experts that are going to help us on this virtual field trip hīkoi called Volcano city.
Actually, right now, Thomas just said we're standing next to what's left from a 180,000-year-old eruption in the Auckland Volcanic Field.
So it's very exciting. Now, Thomas, tell us more about Auckland volcanoes.
Thomas
Pupuke is just one of 53 volcanoes that we have here in the Auckland Volcanic Field. And those volcanoes are spread out across an area, spanning 24 metres from the city centre, from Takapuna in the north to Wiri in the south, and Mount Albert in the west to Mount Howick in the east.
Andrew
So we've got what's left from an eruption, which is a lake. What are some of the other visuals we can see around the city that indicate past eruptions?
Thomas
So we get three main volcanic features in Auckland. The first, like you said, are the lakes like Pupuke behind us, but you also get the maunga or the scoria cones that we call them. And you also get some lava flows, which are like solid crusts of basalt rock that's spanned across the city in some places.
Andrew
Now you were able to tell me that this eruption happened 180,000 years ago. What do scientists do? What information do they collect to find out this information so we can learn more about Auckland's fiery past?
Thomas
So one of the ways that we find out about the ages of the volcanoes and when they erupted is by using ash deposits. And so ashes, particles of fine rock are microscopic. You can't see them with your eyes, but you need a microscope to see. And they get ejected up into the air during an eruption and spread far out from where the volcano actually is.
So they could go tens, hundreds of kilometres away, depending on the wind. And then sometimes they fall into places like lake beds, like the one behind us. And so over time, those get buried as lake sediments, deposit on top of them. Then we can come along and drill down into those, and we get a record of all of the ash deposits that have fallen there over time.
And then by studying those using chemical methods, we can even determine the ages of some.
Andrew
Brilliant. Well, this is just, you know, some of the information we're going to find out about… I said, like, Auckland's fiery past, but also its present and future. And that's something we need to think about. And we're going to find out more about how you can prepare for a potential future eruption.
But thanks, Thomas. Great to start us off…
Thomas
Kia ora.
Andrew
… on our virtual field trip hīkoi.
Kia ora.
The unique features of Rangitoto
Andrew
Well, we've made it to Rangitoto, the iconic landmark here in Tāmaki Makaurau Auckland, and I'm excited to find out more about what makes this volcano so unique amongst the others in the Auckland Volcanic Fields. So let's go and meet volcanologist Annahlise and find out more. Come on!
So this is Annahlise.
Annahlise, you are a volcanologist, an expert on volcanoes, which is great because we're on one right now of course, Rangitoto. But at one point in history, this was erupting, creating the island itself. Tell us about the fiery past of Rangitoto, Annahlise.
Annahlise
Yeah. So about 600 years ago, magma was coming up through the ground and it met with water. So seawater that we see all around the island. And as it did so, it caused an explosive eruption when magma and water interacted. And when it did that, it was breaking apart rocks in the lava and creating a crater in the ground and sending ash; one-metre slick onto Motutapu Island.
And part of that process, it was building a tuff ring of ash on the outsides of that crater. And as the tuff ring got above water level, it transitioned to a dry magmatic type of eruption. And during that it was erupting a frothy magma, creating a rock called scoria. And that scoria built up a scoria cone.
So at around 550 years ago, Rangitoto erupted again. So this time it built two more scoria cones. So one in the centre and one in the south. And from those scoria cones, towards the later stages of the eruption, lava began outpouring from those cones across the island and travelling very far, but gently.
Andrew
Wow. What an amazing picture you've created of the fiery past of this place. And so what are we standing on here right now? What can we see around us?
Annahlise
Yeah. So right across all of here we're looking at a specific type of basaltic lava. So it's called A'a. And essentially when the lava is moving down, it's moving slow enough so a crust forms over it. And as that crust is moving, it's breaking apart into these clinkery boulders.
And another lava that is also produced is called pahoehoe. So that one has a ropy appearance. So think of it like when you're sliding on a carpet and it bunches up into rolls.
Andrew
Well, it's created an amazing landscape! It just looks otherworldly. And of course, you've got these patches of the lava flow. And then on the edges and all around this island is the pōhutukawa forest and other vegetation.
Annahlise
Yeah. So in the barren parts of the lava fields, we're getting mosses and lichens growing. And they are helping the plant ecosystem very much by converting that lava into a nice soil underneath. And plants like the pōhutukawa and going for that, the hollows in between the cracks in the lava, and they're thriving. So we have the world's largest pōhutukawa forest here.
Andrew
Wow! So that is one of the special features of this island. And there's some other quite special features about Rangitoto that sets it apart from the other volcanoes here in Tāmaki Makaurau.
Annahlise
Yeah. So Rangitoto is quite unique, but also puzzling to scientists. So it is our youngest volcano in the Auckland Volcanic Field. And it is the only one to have erupted twice, with two different types of basaltic lava. The other thing that makes it unique is it is our biggest volcano. So the total amount of lava on Rangitoto makes up 41% of the total lava erupted in Auckland. So it's nearly all of the volcanoes combined.
Andrew
Wow!
Annahlise
Yeah. And when we look at the other volcanoes in Auckland, they're quite small and contained. So it makes Rangitoto this kind of oddball volcano.
Andrew
Very interesting thinking about the future and preparing for hazards going forward.
Well thanks Annahlise. Fascinating to learn a bit more about this place, Rangitoto.
Annahlise
Yeah.
Andrew
Kia ora.
Rangitoto kōrero with Kelvin Tapuke
Andrew
Well, here we are on the shores of Rangitoto with Kelvin Tapuke. Now Kelvin, you’ve been having a kōrero with me about where you're from. You want to tell us a bit more about that e hoa?
Kelvin
Kia ora, ngā mihi anō ki a koe Andrew, ki a koutou hoki ngā tamariki mokopuna huri noa i te ao. Tēnei ka mihi atu ki a koutou. Kelvin Tapuke taku ingoa.
My name is Kelvin Tapuke. I'm a senior research fellow at the Joint Center for Disaster Research, Massey University in Wellington. But I come from Ngāi Tai ki Tāmaki through my grandmother, who is a descendant of Te Ngeungeu, who is the daughter of Tara Te Irirangi. In the 1830s, 1820s and the 1850s, [he] was the paramount chief of this side of Auckland. Rangitoto, the island that we are on at the moment, sits within the domain of Ngāi Tai ki Tāmaki Makaurau and Ngāti Tai.
Andrew
Kia ora. And so, well, tell us more about your story; your pūrākau about this place.
Kelvin
Well, our one is our kōrero. So kōrero is knowledge, and knowledge that's been passed down and handed through our families and handed down.
So if we were to talk about all the different kōrero that we have here on Rangitoto, we'd be here for a very long time. And so really, it's just to share in terms of our kōrero.
Now, for our one in this area; I will just refer to this particular part here. In Rangitoto we have a different name for the very top, and it refers to a taniwha called Peretu. Ngā Pona-toru-a-Peretu. Now Peretu is a taniwha that has been named in various areas around here. Te Awanui-a-Peretu is the major channel between Devonport and here, in Rangitoto.
One of the places over in Devonport area, the headlands, is called O Peretu. Now when you put an ‘O’ in front of it, it means that Peretu… it's the place of Peretu or in possession of/by Peretu. So it talks about functionality. In this case it is the place of Peretu. Up here at Rangitoto, you have at the very top, which talks about the various eruptions that have happened a few hundred years ago. And it talks about Ngā Pona, which when you look from afar, you will see the knuckles; the three knuckles of Peretu. So those are the knuckles of Peretu.
Now within the Auckland area when they were proving who is the indigenous tribes to this area. In 1866, Honetaua Te Irirangi, the younger brother of Tara Te Irirangi, presented in the Auckland High Court. So we have on publication and it was mandated by the other tribes. Now we start off with one of our whakataukī, which goes:
Tapuwae o Nuku, Tapuwae Ariki, Tapuwae o Tai. Tihei mauri ora.
Now tapuwae are the footprints. And we have the Sunde site, which is on Motutapu. You would have heard our kōrero from Annahlise; talk about the footprints in the lava that had exploded, in the dust.. in the ash, sorry, over in Motutapu.
Andrew
She didn't mention the footprints, but she did mention the ash.
Kelvin
Sorry.
Andrew
But this is a good story. I like it.
Kelvin
And so in the kōrero in 1866, we can tell you the sex of those footprints. We can also tell you the name of the dog. And so Tapuwae o Nuku talks about the footprints that have been left behind in the ash layers. And Tapuwae Ariki talks about her as an ariki, and the lineage that comes down. Tapuwae o Tai refers to Ngāti Tai and Ngāi Tai, which we are the descendants of those. Now, it's not just a story. It talks about obligations within our geographical areas. And so we are the last of the original tribes, still here, within the Auckland area. And that's very much one of our historical markers for that part.
So just a small kōrero just to share with you kids. When you're looking at Rangitoto, when you look at the very top of it, you have Ngā Pona-toru-a-Peretu.
Andrew
Kia ora, Kelvin. It’s so good of you to share some of that mātauranga with us. Now, of course, the footprints you talk about in the ash that solidify, still remain there. But there are some casts of it at the Auckland Museum, so you can go and see what those footprints in the ash, back from when Rangitoto erupted, what they look like. And there are, as you say, there’s human footprints and a kurī, a dog as well. It’s fascinating.
Kia ora.
Kelvin
Kia ora.
Understanding the volcanic hazards and risks in Tāmaki Makaurau Auckland
Andrew
Well, we're here on Rangitoto. This time with Graham Leonard. He's a volcanologist from GNS Science. This guy knows all about volcanoes. Now they call Auckland ‘the city of sails’. What about, ‘the city of volcanoes’?
Graham, I can see heaps of volcanoes, just standing here.
Graham
Yeah. So from here, just really quickly, I can roughly count about ten volcanoes. You're standing on Rangitoto, and then we have Motukorea, Maungarei, Maungakiekie, Mount St John, Maungawhau. Then you've got The Domain, with the museum sitting on the edge of it. And you've got the two over there on the North Shore.
Andrew
Does the fact that there’s a lot of volcanoes around the city, does that create the risk? Or is it sort of a bit more complicated than that?
Graham
Well, look, volcanoes are a totally natural process, right? We're on the Ring of Fire. We get earthquakes, volcanoes, tsunami. They're a natural part here. They're what a part of us being thrust out of the ocean in the first place. It's 1.5 million people living on top of these volcanoes that's creating a risk to those people.
Andrew
Yeah. So, what are the risks of an eruption?
Graham
The Volcanic Field is about 30 kilometres across, and the city itself is about 30 kilometres right across on exactly the same spot. And it's coming from magma that's about 100km down. And every time it comes up, it takes a different path. That's why there's volcanoes all over the place. So we're not sure where it's going to erupt. And we don't… because it's so far down, we can't pick it up rising right at the beginning. So when we pick it up, it's already on its way. So it could rise quite quickly to an uncertain location.
But what would happen when that magma starts to rise is it's going to be cracking the Earth's crust on its way up through the ground, and that cracking will start generating earthquakes in the rock around it as it’s breaking rock. And we'll pick that up on our seismometers.
And as it comes up further and further, it's going to be, kind of, vibrating the rock around it because it's bubbling magma moving along. And there's gas coming out of it as well, and that creates something we call tremor. So you'd start feeling earthquakes at the Earth's surface. Gas would be coming off the magma, so you might start smelling gas, or it might be CO2, which you're not going to smell, but hopefully we might be able to detect.
And as it gets closer to the Earth's surface, you might start getting steam vents and fumarolic activity; that kind of thing. Ultimately, it's going to erupt. If it erupts like a place like this, where we're close to the water, or there's a lot of groundwater and it's flat ground, it could be quite explosive because it could interact with that groundwater. Or you might get scoria cones from fire-fountaining of magma into the air, or you might get lava flows. And it could go back and forth between those different things.
And then on top of that, there are quite a lot of volcanoes in the last few tens-of-thousands of years. The youngest one, Rangitoto, is only 550-years-old. So… and it's the biggest and it's the most complex. And it's a little bit different from the other volcanoes as well.
So it could happen anytime, anywhere. And because Rangitoto is a bit of an oddball, all bets are off.
Andrew
What are the real dangerous parts? What's the biggest risk to people?
Graham
So the biggest risk in terms of distance from that vent comes from those explosive eruptions from those maar volcanoes. Those big holes in the ground are from explosions that blow out rocks into the air, but more importantly, pyroclastic density currents (PDCs); surges of the kind that come from lots of water and magma.
And they shoot out from the vent and they can go quite a few kilometres; five or six or more kilometres away from the vent. That's the main thing we worry about that might lead to quite widespread evacuation by Auckland Emergency Management.
Andrew
Graham, you talk about picking up tremors in the Earth and detecting gas coming out of the Earth and that sort of thing. Is that the sort of work that scientists are doing to monitor likely future eruptions?
Graham
Yeah. That's right. There's two ways we help manage the risk that comes with living on top of an active volcanic field like this.
We have science research programmes. We have the DEVORA programme – DEtermining VOlcanic Risk in Auckland. So that's co-funded by EQC and Auckland Council. And it's jointly run by GNS Science and the University of Auckland, and has scientists from all over the country involved. And that works on understanding and reducing the risk. And then in terms of the chance of magma coming up under the ground and leading to an eruption, we're monitoring that through the GeoNet programme.
The GeoNet programme is run at GNS Science. And we use the big four of volcano monitoring just like we would do at the other volcanoes around the North Island. We have seismometers positioned around Auckland to pick up earthquakes; earthquakes from magma coming up through the crust and breaking it. And also picking up tremor as that magma and gas comes through the crust.
Then we've got ultra-precise GPS units positioned around Auckland that can pick up the ground deforming by millimetres; very tiny movements. But as the magma comes up, it will be bulging and deforming the ground. And we can pick that up from GPS and also from satellites.
Then the third thing is we've got chemistry. We can look for gas coming out of the ground. I mentioned CO2. We can survey the ground and look for increased CO2. We can watch for sulphur compounds from satellites, and we can put out equipment to monitor for gases.
And then finally there's visual observation. So we can get reports from the public and people in Auckland. We can get webcam observations and we can monitor from satellite observations.
So we bring those together as a monitoring toolbox to hopefully pick up that magma on the rise and give forecast for what might happen to Auckland Emergency Management; to support their decision making and for them to tell the public what they might need to do. And that could quite possibly be evacuation if there was magma on the rise under the city.
Andrew
So it sounds like you've got all bases covered. We can just kick back and relax and just wait for you to let us know.
Graham
Well, unfortunately, that's not the case. It might not be in your lifetime; the risk in a lifetime is relatively low. But it could also happen tomorrow. So you need to be prepared for a whole range of emergencies in your home, including volcanic eruptions in Auckland. And for that, you're going to hear from my colleague Angela Doherty over at Auckland Emergency Management.
Andrew
That’s right, about what we can do to be ready.
Hey thanks, Graham. That was awesome. Really interesting stuff. I appreciate it.
Graham
Kia ora.
Andrew
Kia ora.
Hazard preparedness
Andrew
Kia ora e te whānau. We're here with Angela from Auckland Council. We've been given special permission to come into this room, which is the Emergency Coordination Centre. What goes on in this room, Angela?
Angela
Well, in the Emergency Coordination Centre, we come together with emergency services and welfare support agencies to coordinate the responses to really big disasters and emergencies that are impacting our communities.
Andrew
Right. We've been talking about natural hazards; volcanic hazards in particular. What sort of things should people be doing or thinking about doing to prepare for those?
Angela
Well, luckily, the things you can do to prepare yourself for a volcanic eruption are the same sorts of things you can do to prepare yourself for any emergency or disaster. For example, you really won't be able to tell much difference between a volcanic earthquake and one that's caused by the shifting tectonic plates. So making sure that yourselves and your houses are earthquake ready is really important. And that includes things like fixing your tall or heavy furniture securely to the wall to make sure it doesn't fall on you. And also practising your drop, cover and hold in an emergency and in an earthquake. So that's also really important for volcanoes.
Other things you can do. One of the most wide-reaching impacts of a volcanic disaster is ash. And ash is really bad. It's not the same kind of fluffy ash that you get with wood or paper burning. It's actually pulverised pieces of rock and glass that's covered in acid. So it's really bad for your eyes. It's really bad for your lungs. And it's not great to get on your skin.
But like what we've had to do with Covid, the best way to protect yourself with ash is to actually avoid it. And yes, if you avoid it first. So stay inside if there's ash about. Close your doors and windows. But if you do need to be outside, you're right, get your masks, like a close-fitting mask. Like what we've used during Covid. And eye protection and goggles will protect your lungs and your eyes from ash.
Now, for those other really dangerous volcanic hazards, the best thing we can do is get people out of the way and evacuate. So really, the best thing you can do to protect yourself from a volcanic eruption, or really any emergency, is to get together with your family and create an emergency plan.
Andrew
I was going to say, there's lots of things to think about. So you got to get, you know, with people and make a plan.
Angela
That's right. Yeah. So with your plan, it's also really important, because we don't really know where the next eruption is going to be, we might have to get people out of the way really quickly, and we might not have a lot of time to do that. So ensuring that your plan includes things like where you would go if you were evacuated and what you need to take with you is probably the most important thing.
Having a grab bag is also a really good idea. Like what you might have prepared for a tsunami or a flood to help you evacuate quickly. But remember, you might have to be evacuated outside of the city and for quite a long time. So making sure you include things like the medications your family might need, warm clothes, anything that's really precious to you, your IDs, and even some cash is important to include.
And it's also a good opportunity if you know people in your neighbourhood that might need help in an emergency. Think about whether you can bring them into your whānau and make the plan together to help everybody evacuate at the same time. But the most important thing to remember is evacuations, they can be really scary and they can be very dangerous. So the best thing you can do in an evacuation is keep calm. Be kind and be safe. And always follow the instructions of emergency services and Auckland Emergency Management, because we might be telling you where to go and how to get there safely.
Andrew
That's really good advice, Angela. Get yourself a grab bag. Make yourself a plan. Stay calm.
Angela
And if you need any help of what to include in your grab bag or how to make a plan, you can come to our website, which is aucklandemergencymanagement.org.nz, or the National Emergency Management web page, which is getready.govt.nz. And we've got lots of resources there in multiple languages as well to really help you and your family get prepared.
Andrew
Perfect. Kia ora, Angela.
Angela
Kia ora.
Lava caves and their cultural significance
Andrew
Kia ora e te whānau. I'd like to introduce you to Hannah. Hannah is a geologist with DEVORA. And Hannah has brought us to see a lava cave. But we're standing here on the side of the road in the suburb of Mount Eden, which is very nice. But I've got my hard hat. Where’s the lava cave?
Hannah
So Andrew. You'll never believe it, but right now, we're actually standing on top of the lava cave. And it actually stretches about 100 metres down the road. The cave entrance is on private property, but if you come with me, we'll go take a look.
Andrew
Can't wait. Let's go! Come on.
Andrew
So we've come down into the lava cave. It's so exciting. It's very still and calm in here. There’s not much sound. But if you listen, you can hear drip, drip of water. So it's quite damp as well. But, Hannah, what are lava caves?
Hannah
Right. So, as you can see, there is no red-hot bubbling lava in here anywhere. Essentially, this is a lava tube from a past eruption, and the walls are made out of lava. And now it's accessible from the surface. Much like a cave is.
Andrew
So you say, a past eruption. So which eruption was this tube formed from?
Hannah
So this is actually formed from the Three Kings volcano erupting around 28,700 years ago. And essentially it created the largest crater in Auckland and also produced three volcanic cones, two of which have actually been quarried away.
Andrew
So, Hannah, what's the actual process that forms these lava caves?
Hannah
So lava caves rely on pretty specific conditions in order to form and essentially they need basaltic lava, which is a really runny fluid type of lava that can freely flow down a volcano. And when the lava is in contact with the air, the air is so much colder than the boiling hot lava that it can actually solidify the outside, creating a lava tube; while the inside stays molten and continues to flow like water in a garden hose.
Lava flow through a lava tube can actually flow much further than a regular lava flow, because the tube keeps it insulated and warm.
Andrew
I see. So how far would this one go?
Hannah
So this lava flow is part of the Three Kings volcano, [and] actually extends all the way to Western Springs, which is about three kilometres.
Andrew
So Hannah, we're in quite a modified part of the cave. You can see that the ground beneath us has been smoothed away. But exploring further down, what are some of the features we'll come across?
Hannah
So there are so many cool features in a lava cave. My personal favourite are the lavatites, which are drip features on the surface, on the ceiling, of the lava cave. And essentially they form after the lava tube has been full and it drops down in the ceiling. There's boiling hot lava on the ceiling and it drips down and solidifies really quickly.
Andrew
And they're really sharp. And that's one of the reasons why we've got these hard hats on.
So lava caves here in Tāmaki Makaurau Auckland, is there anything about them that makes them different to lava caves you might find elsewhere in the world?
Hannah
Yeah. So the Auckland Volcanic Field is the only one known in New Zealand to have extensive lava caves. 34 of our volcanoes here in Auckland have produced over 200 lava caves, with more being discovered every month.
Andrew
Cool. So for all you upcoming volcanologists, still a lot more to discover. That’s exciting!
Hannah
And then. So, because our lava caves are so geologically young, they’re actually really close to the surface. And this differs from other places in the world where they are buried quite deep.
Andrew
Can they teach us anything about likely future eruptions?
Hannah
Yes, definitely. So lava flows can show us the paths that the lava took while the volcano was erupting. And the lava tubes left behind show us the direct pathways the lava took.
Andrew
Fascinating. This is so cool in here. I really appreciate your time, Hannah.
We're going to have a little bit of a look around, and then we're going to come back and talk to Kelvin about some cultural aspects related to the lava cave.
Kia ora.
Hannah
Thank you.
Andrew
Kelvin, we've heard from Hannah about the geology of these lava caves. Fascinating stuff! From a cultural perspective, what's the significance of these caves to the mana whenua of Tāmaki Makaurau?
Kelvin
Kia ora, Andrew. That's a great question. As an uri of Ngāi Tai ki Tāmaki and Ngāti Tai ki Tāmaki. I won't speak for all the other tribes, which can fall into the cave areas across the whole Auckland Volcanic Field area, but talk about the significance, in terms of what happens with our tribes.
So as the manutaki for the DEVORA project, which looks at protecting places like these lava caves, it's really important to go back to the different atua that belong to those areas. And so as descendants of those particular atua in those rohe or those particular geographical areas, the lava tubes are really important because they hold the mauri from those different atua and those volcanic events that come through. So the significance of those caves or tubes, they actually carry the life force of the tribe.
Kelvin
If we take for …on top of Maungarei, one of the most significant rua within there is Te Rua o Pōtaka.
And Pōtaka was the big ariki across the Tāmaki Makaurau isthmus. Now a very tapu cave. Still tapu, even though the bones have been removed since the late 1860s, early 1870s. The significance of that tapu still remains within that particular cave system.
Now, not all caves are tapu. Some caves were used as storage pits for kūmara. In other places that you can see, as within this cave, people would come here in times of war or in extreme, dire situations. And that's determined by those people within that area.
Andrew
That's a great couple of examples. I really like that practical use example, but also that deeper, higher connection, you know, that connection to the whenua and those atua.
Kelvin
Yeah. So when people are doing their pepeha or their tūrangawaewae, it's really important to acknowledge that living mauri. It's not a… as you can see within this cave, there's water dripping. There's all sorts of formations that are still part of it. And that's those people. So, when a cave is well, a lava cave is well, those people within that area are well. Likewise, if we've got problems with infrastructure that's going, such as septic pipes, or people, if they're throwing rubbish down or they're making it very dangerous, that makes people unwell as well. So very much, the whakataukī goes:
Ko au ko te – ā, me kī rā – ko Te Rangitoto, ā, ko Te Rangitoto ko au.
I am the lava cave, and the lava cave is me.
Andrew
Kia ora.
Kelvin
Kia ora.
