Investigating the causes and consequences of tsunamis and featuring a case study from Japan, including the Fukushima nuclear accident.
The tectonic plates of our planet are moving - slowly, and constantly.We usually only notice when it results in earthquakes, or volcanic eruptions.But a lot of tectonic activity occurs below the oceans – and it can also have devastating impacts.An earthquake is the sudden release of energy caused by tectonic plates being pushed towards each other - or pushed past each other.When forces build up, large sections of land can be violently displaced.When this happens under the sea, a large amount of water is also displaced – creating a wave.The high levels of energy cause large, high speed waves, which spread out in all directions.And when such a wave hits land, it’s called a tsunami.Anyone looking out to sea as a tsunami approaches would see the water moving in a particular way.First, the sea would recede – as if it was being sucked away.Then a large wave would form, getting taller and taller – before rushing onto the land and breaking.These effects occur as the wave reaches the shallow water of a coastal area. The shallower the depth of the water, the more the front part of the wave is slowed down.With the back part of the wave still moving at higher speed, the water rises up.And the impact as a tsunami wave breaks onto land can be truly devastating…On the 11th March 2011, an underwater earthquake occurred near the coast of the Tohoku area of Japan.The force of the quake displaced a 300 kilometre long section of the seabed.The quake was felt on the land - directly damaging some buildings.But it also created a series of powerful tsunami waves, which spread outwards at speeds of around 640 kilometres per hour.People living in the area closest to the source of the quake had just ten minutes warning as the first wave approached them…and built up to a height of 40 meters.The surge of water devastated entire towns, and at least nineteen thousand people were killed.As the shock from the earthquake was first detected, the reactors of the region’s nuclear power stations were shut down, as an automatic safety measure.But at the Fukushima station, the waves damaged the backup generators, and the cooling system.And in the following weeks, the nuclear cores melted and burned through their containment vessels, releasing high levels of dangerous radiation into the surrounding area.The clean up operation, and the rebuilding of the devastated area, is still not finished.Not all tsunamis are caused by earthquake activity.Anak Krakatau in Indonesia is a volcano that began to rise out of the sea 150 years ago. Its caldera form has been slowly shaped by successive small eruptions.In 2018, monitoring stations detected increases in volcanic activity.In December of that year, a major eruption shook the structure of the cone apart. A huge section broke off entirely and fell into the sea.The landslide caused tsunami waves, at the moment of a particularly high tide… 27 minutes after the collapse, 2 metre high waves struck the inhabited coast of Java.But unlike Japan, the Sunda Strait area isn’t heavily populated.Although thousands of homes and hundreds of ships were destroyed, the casualties were relatively low – with 426 people losing their lives.So the energy of tectonic activity can have terrifying effects as it transmits through sea water…But the exact impact felt by local people will depend on the warning systems they have in place, how many people live in the area, and the magnitude of the event.
The video
Plate tectonics: Tsunamis
Download/print a transcript of this episode (pdf).
This video explores what a tsunami is and what causes them, focusing on two recent tsunamis that rocked Japan and Indonesia, each with very different causes.
On 11 March 2011 a huge underwater earthquake happened off of the Japanese coast, causing a series of powerful tsunami waves which destroyed the reactors of the Fukushima Nuclear Power Plant, releasing radiation into the atmosphere.
On 22 December 2018 an eruption at Anak Krakatau caused an underwater landslide, which led to tsunami waves striking the coastline of Java, Indonesia.
This video concludes with the impact of tsunamis and how they can differ dependent on the warning systems in place and the population density of the location affected.
Teacher Notes
Download/print the Teacher Notes for this episode (pdf).
Teacher Notes prepared in partnership with the Geographical Association.
Before watching the video
- Ask students to recap the causes of an earthquake. This is a good opportunity to revisit the different types of plate boundaries and the hazards that occur at each.
- Ask students to give suggestions on what a tsunami is and what the impact of a tsunami might be. Can students suggest any locations where tsunamis have happened - for example, the 2004 Boxing Day Tsunami in the Indian Ocean.
- Introduce key terms such as:
Tsunami: a series of large, destructive waves that can be caused by earthquakes, volcanic eruptions or landslides into the ocean.
Displaced: the shifting of land or rock - for example, the movement of plates under the ocean can displace large areas of water, forcing them upwards to cause a tsunami wave.
Nuclear power: electricity generated by power plants that derive the required heat from the process of fission in a nuclear reactor.
Landslide: a collapse of a mass of earth or rock from a volcano, mountain or cliff.
Magnitude: a measure of the size of an earthquake or the amount of energy released by an earthquake.
While watching
You may wish to stop at relevant points during this short video to pose questions and check understanding, or wait until the end. Useful questions might include:
- What is an earthquake?
- What is a tsunami?
- What would you see before a tsunami wave hits the coastline?
- What caused the tsunami that hit Tohoku in Japan in 2011?
- How did the people living in Tohoku know that there was going to be a tsunami?
- What impacts did the tsunami have on Tohoku?
- What happened at the Fukushima nuclear power plant?
- What caused the tsunami that hit Java?
- What impacts did the tsunami have on Java?
- What factors can alter the impacts of a tsunami?
After watching
- Look at a map of where tsunamis have occurred. Ask students to describe any patterns they can identify - for example, do they occur in certain oceans or close to plate boundaries?
- Task students to create a storyboard on how a tsunami is formed. Students can then use this to help them explain the causes of a tsunami. They may want to create two pathways - one for an earthquake being the cause, and the other for the volcanic eruption and landslide that occurred in the Sunda Strait.
- Completing further research on one of the two events in the film, students could create a timeline of events from the cause to the response and recovery efforts. Students can then use this information to help them to create a table of impacts associated with tsunamis. This table should be divided into ‘social’, ‘economic’ and ‘environmental’ impacts. They may also want to consider what can affect the impacts and how they are experienced - for example, having working warning systems and evacuation routes.
- With the research completed by students they could write a disaster report or a newspaper article which includes the causes, impacts and the responses to the tsunamis. They could take their report one stage further by giving recommendations on how governments and scientists could help coastal communities to prepare for tsunamis.
Where next?
- Tsunamis may be rare, but when they do occur they cause widespread destruction.
- Research the 2004 Indian Ocean tsunami. How does it compare to the two tsunamis studied in the film?
- On 26 December 2004 an earthquake with a magnitude of 9.1 struck off the coast of Sumatra, Indonesia. It caused widespread devastation across southeast and south Asia.
- Students could also research the limited warnings that were given. In 2004 tsunami warning technology was not as sophisticated as it is today. As a result of the 2004 tsunami, research and development was undertaken to improve early warning systems around the world.
Links
Plate tectonics:
http://unitedkingdom.bahce.site/bitesize/topics/zn476sg/articles/zrcgr2p
Plate margins and plate tectonics:
http://unitedkingdom.bahce.site/bitesize/topics/zqvb7v4/watch/zyk46rd
Earthquakes and tsunamis:
http://unitedkingdom.bahce.site/bitesize/topics/zn476sg/articles/zc4rcmn
Curriculum notes
This video is suitable for teaching KS3 in England and Northern Ireland, 3rd/4th Level in Scotland and Progression Step 4 in Wales.
In the English National Curriculum this film can be used to help teach the following:
- Physical geography relating to geological timescales and plate tectonics.
Resources
Teacher Notes
Download/print the Teacher Notes for this episode (pdf).
Transcript
Download/print the transcript for this episode (pdf).