To explain how tsunamis are created

To discover their impact and how people respond

How do tsunamis form?

Key terms: Tsunami, drawback, megathrust, train

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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.

TsunamigenesisTsunamigenesis 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.

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!

Tsunami AnatomyIn 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.

Japan’s Tsunami: How it happened?

Watch the video and make notes under the headings.

Causes Why and how it happened?

EffectsWhat were the impacts on people?

ResponsesWhat did Japan government and people

do?