Volcano Q&A with Ben Kennedy

Professor Ben Kennedy, volcanologist and award-winning science communicator, took questions from ākonga during an ‘Ask a scientist’ session hosted by Science Alive and the Science Learning Hub (SLH).

Asking questions is a hallmark of science and asking curious questions is a great way to begin ākonga-led inquiry. The key science concepts discussed in the Q&A include plate tectonics, plate boundaries, the Pacific Ring of Fire, magma generation, volcanic seismicity and how scientists use information to forecast volcanic eruptions. Ben’s answers are tailored for mid-upper primary students.

Exploration is an important part of being a scientist

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Professor Ben Kennedy is a volcanologist from the University of Canterbury. He travels to different volcanoes in New Zealand and around the world to figure why they erupt and how we can manage volcanic hazards.

Rights: Prime Minister's Science Prizes

Referencing Hub media

I am just like you guys, I’m just a kind of kid who is excited about volcanoes and rocks and I love exploring volcanoes all over the world.

You can watch Ben answer questions in the video below. We also have a transcript of the Q&A along with links to resources that support student learning. The transcript has timecodes if ākonga have specific questions and would like to watch the corresponding sections of the video. (See below.)

Question: Have you ever seen a volcano erupt and what was it like?

(01:26) Some of my favourite things to do in the whole world is to watch a volcano erupt – from a safe distance of course. Actually, you can see right behind me here up on my wall, these are all photos that I have taken of volcanoes erupting. So you can see this one here is a volcano in Guatemala. This one’s a volcano in Chile. Up there, there’s a volcano in Italy. So yeah, I’ve probably seen about 10 different volcanoes all over the world erupting. It’s very exciting. A little bit scary but that kind of makes it even more exciting. But I’m always very careful to make sure that I’m safe and far enough away.

Question: How do volcanoes form?

(02:12) Well, volcanoes are really just piles of lava. So if you imagine from deep inside the Earth, there’s molten rocks, and that comes up, rises up out of the Earth. It reaches the Earth’s surface, and that molten lava turns into – well, it’s magma when it’s underground, but when it reaches the surface, it’s lava – turns into rocks and builds a little pile. So when a volcano first comes out of the ground, there might be no volcano there at all. It might just come up in a field. And then the volcano, a bit of lava comes up, volcano grows, might explode a little bit, some ash might fall down. It grows a bit bigger, might erupt again, another bit of lava. So you’re building layers of lava and ash, and your volcano slowly grows out of the ground.

Additional information of volcanic formation:

• Magma on the move – SLH article

• Rotorua caldera formation – SLH video

• Calderas in the sandpit – SLH activity

• Tsunamis in the sandpit – SLH activity

Question: How do you know when a volcano is going to erupt? How do you check?

(03:16) This is one of the things that volcanologists spend a lot of their time scratching their head, trying to work out how we know when a volcano’s going to erupt. So the most useful way is we use special fancy machines called seismometers and they can measure tiny little earthquakes. So when magma is moving underground, under your volcano, it’s coming up, and the volcano starts to shake a little bit. And if you have a machine on the side of that volcano, it can measure how much shaking and can tell you whether the magma is deep or if it’s coming up shallow. So earthquakes and seismometers are the best ways to measure when a volcano’s going to erupt. But we have other ways. We also can measure the gas that comes out of the volcano. Again, you can use fancy machines called spectrometers that can measure the gas that comes out of the volcano. And as the magma’s getting closer to the surface, it might get more and more smelly up above the volcano and you can use these spectrometers to measure how smelly your volcano’s getting and whether or not it might be erupting soon. And every year, we invent new ways to try and better predict and measure when a volcano might erupt.

Additional resources on how volcanologists measure possible eruptions:

• How we monitor volcanoes – GeoNet

• Volcano monitoring – article and video – Earth Sciences New Zealand

• Determining Auckland’s volcanic risk – SLH article

• The search for Auckland’s volcanic past – SLH article and infographic

• Volcanology methods – SLH article

• Seismometer – SLH image

Question: How long does it take for a volcano to rise and form?

(04:45) There haven’t been many examples of when we’ve seen a volcano get born from nothing. But there was one volcano in Mexico. There was a farmer who was working in his field one day and he felt a few earthquakes and out of nowhere a volcano started erupting in his field. And I think it went from nothing to a pretty decent sized volcano in about maybe about 10 years. But volcanoes can actually keep growing for hundreds of thousands of years. So Mount Ruapehu, for example, or Mount Taranaki in New Zealand are very big volcanoes and they took something like 200,000 years to get that big. So in about 10 years, you can get a little volcano. But if you wait for hundreds of thousands of years, then the little volcano can grow slowly into a very big volcano.

Additional resources on volcanic formation:

• Rangitoto – Auckland’s largest volcano – SLH article and infographic

• Rotorua caldera formation – SLH video

• Volcanoes – timeline – SLH article

• Parícutin facts for kids – Kiddle encyclopedia article

Question: When will a volcano explode?

(05:58) That’s a question again that we spend a lot of time thinking about. And usually, as I was saying, remember we were using those seismometers to measure how much the volcano is shaking? So one way you can do is you can see a volcano might do a little bit of shaking, and then it might do a bit more shaking, and then it might do lots of shaking, and then it might be shaking all the time – and when it’s shaking all the time, that probably means it’s about to erupt! So you look at those changes in the amount of shaking over time. So if you’ve got a volcano that’s doing lots and lots of shaking, it means it’s about to erupt.

Additional resources on how volcanologists measure possible eruptions:

• Determining Auckland’s volcanic risk – SLH article

• The search for Auckland’s volcanic past – SLH article and infographic

• Volcanology methods – SLH article

• Seismometer – SLH image

Question: How do underwater volcanoes not fill up with water?

(06:50) We do have thousands of volcanoes underwater, and I guess when they’re not erupting, they probably are actually filled up with water. I never really thought about this but volcanoes are a bit like sponges. So they’ve got lots and lots of holes in them and the water will fill up on all of those little holes underwater. But as the magma rises up into these volcanoes underwater, it will erupt through the water and sometimes actually the water can make the volcano explode even more than it would do normally. And it actually depends a lot on how deep those volcanoes are. So sometimes you can have a volcano that starts off underwater and it grows and grows and grows and then becomes an island as it pokes out at the top of the sea. Or sometimes it’ll stay underwater. Volcanoes will actually fill up with water, and when they erupt, that eruption will push the water out of the way.

Additional resources about underwater volcanoes:

• Why the volcanic eruption in Tonga was so violent, and what to expect next – SLH article

• A year on, we know why the Tongan eruption was so violent – SLH article

Question: Can volcanoes erupt other substances?

(08:19) I love rocks, and you can see I’ve got lots of rocks over here and you can see they’re all different colours. So sometimes a volcano might erupt this type of material, which is called pumice. It’s very light and it’s white. Sometimes a volcano might erupt big, heavy bombs that fly through the air like this. And sometimes volcanoes might erupt spiky lava, comes out. So volcanoes can erupt all different types of rocks and it might depend on how long the volcano’s been waiting to erupt. It might depend on whereabouts on the Ring of Fire or the tectonic plates those volcanoes are.

Additional resources about substances that erupt from volcanoes:

• Types of volcanic rock – SLH article

• Lava flows from Auckland’s volcanoes – SLH article and infographic

• Volcanic gases – impacts on air quality – SLH article and infographic

• Lost – a hot rock – SLH activity

• Making lava fudge – SLH activity

Question: Are there any volcanoes erupting on the Pacific Ring of Fire?

(09:26) New Zealand is on the Ring of Fire. So we have our own volcanoes on the Ring of Fire and each one of those volcanoes will erupt different types of magma. So yeah, some of them will erupt the white pumice. Some of them will erupt the dark basaltic lava and it will just depend exactly how long the magma’s been sitting underground and what it’s been doing underground.

Additional resources on the Ring of Fire:

• New Zealand volcanoes – SLH article

• The Pacific Ring of Fire – SLH image

• Tectonic jigsaw puzzles – SLH activity

Question: How do volcanoes get the power to erupt?

(10:00) The secret power of volcanoes comes from gas. So inside a volcano, there’s lots of gas and that gas helps to build the pressure, and once you’ve got pressure, that gives you the power to erupt. So if you’ve got a gas bubble that’s wanting to expand and it’s trying and it’s trying and trying to expand and it’s building up pressure, it’s building up pressure and pressure and pressure and then boom! That’s basically how you get the power of volcanoes. It’s gas wanting to expand and usually that gas is actually water vapour – just like when you boil a kettle in your kitchen, you see that water vapour coming off your boiling kettle. That is the volcano power right there.

Additional resources on what powers and triggers an eruption:

• Magma on the move – SLH article

• Volcanic gases – impacts on air quality – SLH article and infographic

• Curious kids: Why do volcanoes erupt? – The Conversation article

Question: Why did you decide to study volcanoes?

(10:58) I just think volcanoes are really cool. I think they’re exciting. I think they’re beautiful. I love going hiking on volcanoes. I love picking up rocks. I think volcanic rocks are really pretty. Here I’ve got some obsidian that I found on a volcano. Yeah, just I love walking around volcanoes and I’m really interested in working out – just like you guys are asking those questions – why do volcanoes erupt? It’s an interesting question that it’s a good puzzle that I’m still trying to solve.

Additional resources about volcanic rocks:

• Volcanic rocks – SLH resource curation

Question: Why are volcanoes important for you?

(11:42) They’re important for me – one, because it’s important to try and keep people safe. So part of my job is trying to work out where is safe to go on a volcano and where is it not safe, so I think that’s important. I just think volcanoes are really fun too. I just think they’re really fun to visit. I think they’re cool. They make me smile. Yeah, I just like them.

Additional resources about Ben and his interest in volcanoes:

• “Volcano dad” wins Prime Minister’s Science Communication Prize – article and video – Prime Minister’s Science Prizes

• Meet Ben Kennedy – Volcanologist – video – LEARNZ

Question: Why is there water on the top of a volcano?

(12:26) Some volcanoes like Mount Ruapehu have a lake at the top of them. And on Mount Ruapehu, there’s two reasons why there is water on top of Ruapehu. The first reason is, remember I was saying that, just like your kettle, there’s actually water coming out of your volcano. So there’s actually water being added to the lake from below – from the volcano, but there’s also water being added from the top because it rains a lot on volcanoes and if you’ve got a cup at the top of your volcano, which is your crater, and it’s raining, that cup will just fill up. So it’s being filled up from above with rain and it’s being filled up from below by volcanic gases. So two reasons.

Additional resources about Ruapehu’s crater lake:

• Image of Te Wai ā-moe – Ruapehu Crater Lake – Wikipedia

• Ruapehu activity bulletin updates – GeoNet

Question: How many active volcanoes are there in the world, and where are the most?

(13:25) I don’t actually know the answer to this and I think probably if you asked every volcanologist in the world, they would give slightly different answers. But there are thousands, thousands of volcanoes. Some of them are active, some of them are not. There’s definitely hundreds, probably even a thousand or a couple of thousand that are still active. Because for a volcano to be active, it doesn’t mean it’s erupting right now. It just means that it’s erupted in the last 10,000 years. So there are lots and lots of volcanoes that have erupted in the last 10,000 years. So yeah, I would say hundreds and maybe even thousands, and probably some of the places where there’s the most is around that Ring of Fire. So around the Ring of Fire, there are lots and lots of volcanoes. Places like Indonesia have, I think, some of the highest concentrations of volcanoes in the world because that’s on the Ring of Fire. But we also have lots of those underwater volcanoes as well.

Additional resources on active volcanoes and the Ring of Fire:

• Volcanoes of the world – Volcano Discovery

• New Zealand volcanoes – SLH article

• Tectonic jigsaw puzzles – SLH activity

Question: How much lava can spit out of a volcano, and what causes it?

(14:42) Sometimes a little bit of lava may come out and you might just make one big, long lava flow. But sometimes there are volcanoes called super volcanoes and they can erupt so much lava – lava and ash and pumice. And that could be hundreds of cubic kilometres, which is really hard to imagine, which is probably areas that are as much lava that would cover Auckland completely in lava, and then that lava would go up, up, up and go high up into the sky. So just kilometres and kilometres and kilometres of lava. And you can’t even imagine how much it is.

Additional resources about lava and lava flows:

• Magma on the move – SLH article

• Lava flows from Auckland’s volcanoes – SLH article and infographic

Whakaari/White Island

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The summit of a submerged stratovolcano (a type of cone volcano). Measuring from the seafloor, the volcano is over 1,900 m in height and is still active, releasing gases and steam regularly. The most recent eruption was in December 2019.

Acknowledgement: GeoNet

Rights: GeoNet

Referencing Hub media

Question: Which volcanoes in Aotearoa New Zealand could erupt?

(15:47) Whakaari White Island is actually erupting right now. It’s just puffing out small amounts of ash that can be seen on the satellites. Other volcanoes that could erupt is Mount Ruapehu is probably the next most likely. Also Mount Tongariro. Then you’re probably going to think about Mount Taranaki and even some of those volcanoes in Auckland. So yeah, they’re probably the most likely ones. There’s also some volcanoes around Rotorua that could erupt as well. So we actually have quite a lot. We have eight or 10 volcanoes in New Zealand that could erupt.

Additional resources about Aotearoa New Zealand’s volcanoes:

• New Zealand volcanoes – SLH article

• Volcano map of New Zealand – SLH interactive

• Auckland Volcanic Field – SLH interactive

• Types of volcanoes – SLH article

• Exploding Taupō – SLH article

• Volcano hunt – SLH activity

Question: How do you tell if a volcano is extinct or not?

(16:45) It’s actually a question that, as volcanologists, we don’t have a good answer to. So one thing is if it just hasn’t erupted for a million years then you can pretty safely say it’s extinct. So we’ve got some volcanoes near where I live in Ōtautahi Christchurch, Banks Peninsula, and they haven’t erupted for 6 million years, so that’s really a long time. So we’re pretty sure those ones are extinct but it’s actually very hard to know. So some volcanoes can be sleeping or dormant for a very long time. So remember when I was saying those things – you can measure the earthquakes, you can measure the gas, you can have a look to see whether the ground is moving slightly, and you could see if the volcano is breathing and he’s still asleep underground. So there are lots of different ways but mostly we decide if it just hasn’t erupted for a very, very long time, then we say it’s extinct.

Additional resources on the history of volcanoes in New Zealand:

• Volcanoes – timeline – SLH article

Question: Does lava cause fire?

(18:00) Sometimes lava can set things on fire. There were some eruptions in Iceland recently where some lava’s started little bushfires around. I’ve even got on my desk here, if you can see this, this is a bit of charcoal. So there was a big eruption from Taupō and that burnt whole forests down and turned the forests into charcoal. So there was a big, big fire probably associated with that eruption. So sometimes volcanoes, if they erupt into dry wood, can start fires.

Additional resources about the risk of fire from lava:

• Lava flows from Auckland’s volcanoes – SLH article and infographic

Question: How long does it take for a volcano to erupt?

(18:58) Every volcano is a bit different. It’s a bit like people. Sometimes someone might get angry and stay angry for a very long time. They might be angry for days or weeks, and sometimes someone might get angry and then, 5 minutes later, they’re all better. So volcanoes are bit like that. They all have different personalities. So some may erupt just once for 20 minutes and then not erupt again for another 100 years. Or some volcanoes might start erupting – there are some volcanoes that have been erupting constantly for a hundred years. Actually, this volcano here – that volcano there is Stromboli in Italy – and it’s been erupting for hundreds of years. Since the Roman times, it was erupting and it hasn’t even stopped. It keeps erupting every few minutes.

Additional resources about long-lasting eruptions:

• What volcanoes have had the longest eruptions? – Smithsonian Institution

Question: How long does it take for a volcano to become a mountain?

(20:05) It’s a bit like that question where somebody has asked how can a volcano become extinct? Some people could call an extinct volcano a mountain. So just like I was saying – there are those, I guess it depends how big it is, but there are mountains that are made of volcanic rocks. So might, again, might be a mountain that’s again a few million years old and it’s been eroded and there’s been landslides and it’s got all pointy and it doesn’t look like a volcano any more because it’s been collapsed and pushed up and squished by other rocks. So I would say a few million years and you could turn a – maybe I would say, I would go for 10 million years if I was going to pick a number out of the air before you can really call a volcano, I guess, when it stops looking like a nice cone because it’s been eroded so much.

Additional resources on the history of volcanoes in New Zealand:

• Volcanoes – timeline – SLH article

Question: What tools do you use to measure the temperature inside a volcano?

(21:09) If we’re trying to measure the temperature of a volcano, we use a thermometer. So a bit like you guys when you – if your mum’s worried that you’ve got a fever or something – they might put a thermometer in your mouth. We have thermometers to measure how hot volcanoes are but they tend to be very special thermometers that are made out of very special mixtures of iron and nickel that are quite strong and won’t melt. So they’re special thermometers called thermocouples and that won’t melt, and we use that to monitor the temperature of volcanoes. And sometimes those thermometers might be connected to a satellite so you can have a thermometer in a volcano out on an island. That information then bounces off a satellite, comes back to our computers, and then we can measure, see how that temperature is changing on the volcano even though we’re not there.

Additional resources about volcanic monitoring and measurement:

• Our remote volcano monitoring toolkit – GNS/Earth Sciences New Zealand

• Using thermocouples and satellite sensors – USGS

Question: What equipment do you need to go into an active volcano?

(22:12) It depends what your job is. So sometimes a volcanologist is going and he’s there to collect rocks, right? And if he’s there to collect rocks, he might bring a hammer because he needs to break off a bit of rock. If he’s there to mend some equipment – maybe there’s been an eruption and your seismometer is broken – then you might go and you might need a whole bunch of equipment in order to fix something. If you are going to measure a temperature, you might have your thermocouples. If you’re going to take gas samples, you need these special glass bottles to suck gas out of the fumarole, which is where the gas is coming out of the volcano. What else? If you’re going to sample lava – so sometimes on TV you might have seen volcanologists wearing a big silver suit, and then these are heatproof suits, and then you can go up and scoop lava out of lava flows, wearing a special heatproof suit. I’ve got to wear one of those suits before. It’s pretty good fun.

Question: Why are there so many volcanoes in Iceland?

(23:23) Iceland is one of my favourite places to visit because there are so many volcanoes there. And the reason is Iceland is in a very special part of our planet where – if you remember our planet, it’s all got tectonic plates around it and sometimes those tectonic plates are moving apart, sometimes those tectonic plates are moving together. In Iceland, they’re moving apart and as they’re moving apart, this means magma from deep inside the Earth will rise up. So these two plates are moving apart and then there’s a big plume of magma coming from deep inside the Earth that’s rising up and leaking out of those cracks where the Earth is being torn apart by two plates moving apart.

Additional resources about Iceland’s volcanoes:

• Iceland’s volcanoes – LEARNZ

• The land of fire and ice: A guide to volcanoes in Iceland – Iceland Air

Question: How hot can a volcano get before it erupts?

(24:17) We have measured the temperature of lava when it’s coming out of the volcano and it can get to 1,200°C. So really, really, really hot. That’s hot enough to melt rocks.

Question: Is it common for volcanoes to erupt in the ocean?

(24:44) It is. It’s surprisingly common for volcanoes to erupt in the ocean, but often we don’t even know it’s happening because the ocean is very deep in some places and there might be volcanoes erupting underwater all the time that we don’t even know about. So yeah, it is common and we don’t know exactly how common. We need actually to get more measurements, more equipment on the bottom of our oceans to measure those underwater volcanoes.

Additional resources about underwater volcanoes:

• Why the volcanic eruption in Tonga was so violent, and what to expect next – SLH article

• A year on, we know why the Tongan eruption was so violent – SLH article

• Tsunamis in the sandpit – SLH activity

Question: What’s the reason for all of the magma rising up and why is it red?

(25:20) I think those two things are related because hot things glow red, so that’s why it’s red. And also hot things like to rise. They’re more buoyant. It’s a bit like when you see a hot air balloon with all that hot gas. That’s why the hot air balloon rises up in the sky. And if you can imagine magma underground, it’s really hot and it’s glowing red and it also means it’s lighter than the rock around it, and it pushes up through the rock like a really slow-rising hot air balloon.

Additional resources about magma’s movement towards the Earth’s surface:

• Magma on the move – SLH article

• Volcanic gases – impacts on air quality – SLH article and infographic

Question: Have you ever discovered a volcano?

(26:10) I’ve got a good story about that actually. So I thought I’d found a little volcano on the side of Mount Ruapehu that nobody knew was there before. It wasn’t on any of the maps. And I talked to all my scientist friends and they were like, “Ah, that’s a new volcano! You found a new volcano!” And then I talked to the local iwi, the local Māori and they were like, “Oh yeah, we know about that volcano. We’ve known about that for ages. It’s in all our stories.” So yeah, I think that’s a good lesson there – that there’s a lot of knowledge there with the local iwi. So yeah, I thought I’d discovered a volcano but turns out I hadn’t.

Question: Any comments for our future scientists?

(26:57) I think keep having fun and keep smiling. And I don’t know – I love collecting rocks. I love exploring, and yeah – keep that up. Keep asking questions. That’s what you’re doing and those questions are brilliant. So more more questions!