Video

Modelling a tsunami

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

Rights: Beneath the Waves project
Published:23 February 2024