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  • Rights: Beneath the Waves project
    Published 23 February 2024 Referencing Hub media
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    A stratocone volcano is a steep pointy volcano. If the magma chamber within the volcano grows, it can make the volcano unstable and cause it to collapse. If the volcano is in the sea, this massive disturbance can generate a tsunami.

    Dr Graham Leonard, a natural hazard scientist and geologist with GNS Science, works with students from Te Kura o Te Pāroa to model the collapse of a magma chamber and the tsunami wave it generates.

    Questions for discussion

    • In this model, what does the balloon represent?
    • What does the water represent?
    • What does the sand along the edge of the container represent?
    • How does this model represent a collapse at Whakaari/White Island?
    • Do you know of other locations where this type of collapse has caused a tsunami?
    • What are the strengths of using this activity to model a tsunami caused by a huge disturbance in or under the water? What are the drawbacks?

    Transcript

    Dr Graham Leonard

    Why do you think we’ve got sand and water out for this experiment? What do you reckon we’re gonna …

    Student

    A volcano.

    Dr Graham Leonard

    Yeah. So the sand is gonna be the volcano. And why are we using water, what’s the other thing?

    Student

    A tsunami.

    Dr Graham Leonard

    Yeah, totally. We’re going to make a volcanic island – this is Whakaari, and we’re gonna finish it in a minute. And this is the coastline nearby. What’s the name of the town near Whakaari?

    Students

    Whakatāne?

    Dr Graham Leonard

    Yep. Can you guys help me now? Take two hands, like a double scoop like this, and gently build me a volcano over my magma chamber please.

    Student

    Oh, so like carry over the sand?

    Teacher

    Someone else grab the pump. Magic. Yep.

    Student

    Can I have a go?

    Dr Graham Leonard

    Yep. Stop.

    Student

    Sorry. Whoa. Slower?

    Dr Graham Leonard

    Yep. Just a little bit. You’re going to get to blow it properly in a minute but we’re going to build a volcano first. So take all of the sand in big double scoops – with two hands, yeah, and build me a volcano on top. So don’t be shy – just like this. Cool. Now we’re making a big volcano, keep going.

    Student

    Oh, I want to see what happens.

    Dr Graham Leonard

    Keep going. We want to go real high and pointy. Just like in a Disney movie.

    Student

    So we’re building Whakaari or …

    Dr Graham Leonard

    We’re building Whakaari, exactly. So Whakaari has in its past often been quite a pointy volcano. OK, add the rest on and don’t pack it down – just put it on gently – on top. Yep, cool. Now, time to come up with an idea, and in science, what’s our word for idea?

    Student

    Hypothesis.

    Dr Graham Leonard

    Yeah, totally. So come up with a hypothesis. So when we inflate the magma chamber – more magma inside the volcano – what do you think is going to happen slowly?

    Student

    Explode.

    Dr Graham Leonard

    It could explode, yeah. That’s one idea – one hypothesis. What else might happen if we just keep expanding it without it exploding?

    Student

    Break the volcano.

    Dr Graham Leonard

    Yeah. And can you describe that a bit? Will it collapse? OK?

    Students

    It will release the air pressure. Destroy it.

    Dr Graham Leonard

    And if it collapses, where’s it gonna go?

    Student

    Flow out the sides.

    Dr Graham Leonard

    Yeah, it’s gonna collapse into the …

    Student

    Ocean.

    Dr Graham Leonard

    Yeah. And then if it disturbs the ocean, what do we call that?

    Student

    Tsunami.

    Dr Graham Leonard

    Yeah! And over here …

    Student

    Is us.

    Dr Graham Leonard

    What have we got? This is us, yeah? And these are little …

    Student

    Houses.

    Dr Graham Leonard

    These are little whare near the coast and they’re above the waterline, but should we see if our volcano is big enough to cause a collapse and cause a tsunami that will reach the whare? So that’s our hypothesis and now this experiment is going to test it.

    So can you slowly pump up the magma for me, please? Yep – yeah, you’re right. Keep going. Bit faster now. Go. Keep going. Keep going. And watch the houses.

    Students

    Oh!

    Dr Graham Leonard

    Oh, one or two are OK – they’re a bit higher ground. You’re done, you’re done. All done.

    Teacher

    So you notice the ones on higher ground?

    Student

    Yeah.

    Teacher

    These ones are OK. You see where the water’s come to?

    Dr Graham Leonard

    Yeah.

    Student

    Oh, so the balloon expanded, which meant the …

    Dr Graham Leonard

    Totally.

    Teacher

    So what kind of volcano is that – do we think, guys?

    Students

    Ummm … pointy, active.

    Teacher

    Pointy? Yeah, it is active.

    Dr Graham Leonard

    What does Whakaari, what does Whakaari look like now?

    Students

    Oh! Like that!

    Dr Graham Leonard

    Yeah! And why do you think it looks like that?

    Students

    Ahhh! Cause it collapsed.

    Dr Graham Leonard

    Cause it collapsed – just like your experiment.

    Acknowledgements

    Dr Graham Leonard, GNS Science, Beneath the Waves MBIE Endeavour project
    Professor Ben Kennedy, University of Canterbury, Beneath the Waves MBIE Endeavour project
    Te Kura o Te Pāroa
    Drew Mehrtens, University of Canterbury

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