1. L How do tsunamis form? To explain how tsunamis are created
To discover their impact and how people respond
How do tsunamis form?
Key terms: Tsunami, drawback, megathrust, train

2. Japan Earthquake and Tsunami 2011
On Friday 11 March 2011 Japan’s worst natural disaster took place. A tsunami was triggered by a 9.0 earthquake.

3. Tsunamigenesis
Tsunamigenesis is a posh geographical term for the creation of tsunamis. Tsunamis are most commonly created by earthquakes.
An earthquake occurs along a boundary (or faultline) under the ocean. This thrusts up the ocean floor, moving the entire ocean above it.
The worst tsunamis are created by mega-thrust earthquakes. These are earthquakes over 9.0 on the Richter Scale and result in the ocean floor thrusting upwards.

4. You need to run!
This is drawback. Before a tsunami wave strikes, the ocean is sucked back. Fish are often stranded and huge areas of the shore are revealed. You have minutes to escape before the waves begin to hit! This saved a girl and her family in Indonesia in 2004 – she learnt about it in a geography lesson!

5. Tsunami Anatomy
In the open ocean tsunami waves may only be 1 or 2 metres high.
As the waves approach land the friction with the sea bed slows the waves and their height increases. They may be up to 20 metres high when they crash into land!
Tsunami waves continue to hit the coast for hours after the earthquake. This is known as a train of waves.

6. Japan’s Tsunami: How it happened?
Watch the video and make notes under the headings.
Causes Why and how it happened?
Effects What were the impacts on people?
Responses What did Japan government and people do?