Tsunamis in the sandpit
Stratovolcanoes are steep-sided, cone-shaped volcanoes. If the magma chamber within the volcano grows, the expansion can break the flanks of the volcano and cause it to collapse – creating a landslide. If the volcano is in the ocean – like Te Puia Whakaari/White Island or Indonesia’s Anak Krakatau – the debris can quickly displace/push a large volume of water and generate tsunami waves.
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?
In this activity, students use a balloon in a container of sand and water to model how volcanic eruptions can generate a tsunami.
By the end of this activity, students should be able to:
demonstrate how magm a chambers expand and the effects this expansion may cause
demonstrate how a horseshoe-shaped crater is formed by a lateral eruption
demonstrate how tsunami waves are generated by a landslide
identify Te Puia Whakaari/White Island and Anak Krakatoa volcanoes and tsunamis and discuss their formation.
Download the Word file (see link below).
Related content
We have a wide range of related resources curated in these handy introductory articles below:
Researchers discovered that the large underwater Hunga Tonga–Hunga Ha’apai volcano had a hidden caldera 150 m below the waves. Read about the devastating volcanic eruption in January 2022, the tsunami that followed and what we might expect next. Find out what scientists have discovered a year after this eruption in this article.
Activity idea
The Rotorua geothermal area was formed by a massive caldera. Watch the Rotorua caldera formation animation then go outside and conduct the student activity Calderas in the sandpit.
Useful links
The International Tsunami Information Center has information on the 2018 Anak Krakatau volcanic eruption. The before and after photos demonstrate the striking cone shape prior to the eruption and the horseshoe-shaped caldera after the eruption. This simulation shows the tsunami event that followed.
Acknowledgement
This activity was developed by Kathleen Sibuea, a graduate student at the University of Canterbury. The activity uses a model developed by Dr Graham Leonard, a natural hazard scientist and geologist with GNS Science, and Professor Ben Kennedy at the University of Canterbury.
The project received funding from GNS Science Beneath the waves.
