Collins Big Cat — TSUNAMIS: Band 12/Copper

Copper Band 12

What•is•a•tsunami?• TSUNAMIS

How•do•they•happen?• What•effect•do•they•have• on•people’s•lives?• Learn•about•how•we• can•predict•them•by• looking•at•the•science• behind•them•and•some• real-life•case•studies.••

Browse the complete Collins catalogue at

www.collins.co.uk

An•information•book

ISBN 978-0-00-820873-8

9 780008 208738 www.collins.co.uk/collinsbigcat

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Collins•Big•Cat•Inform•is• a•large•range•of•topical• non-fi•ction•to•support• the•curriculum.

Emily Dodd 6/19/19 8:23 PM

Written by Emily Dodd

Contents What is a tsunami?

2

Normal waves

4

Tsunami waves

6

Earthquakes and tsunamis

10

Case study: Boxing Day Tsunami, 2004

12

Landslides and tsunamis

14

Case study: Lituya Bay, Alaska, 1958

16

Volcanoes and tsunamis

18

Case study: Krakatoa, 1883

20

Predicting tsunamis

22

Living with tsunamis

24

Living after tsunamis

26

Glossary

28

Index

29

Tsunamis – causes and protection

30

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What is a tsunami?

A tsunami is a fast, powerful, dangerous series of waves or wave.

Tsunamis are usually caused by a movement of the seabed which pushes the water above it into waves. The waves start small when they are out at sea; you wouldn’t know it was a tsunami if you were in a boat floating on the water. But as the waves come towards the land, they increase in height and are powerful enough to bring large volumes of seawater inland causing flooding and devastation.

The word “tsunami” means “harbour waves” in Japanese.

Tsunamis are more common in Japan so that’s why we use their word for them.

2

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Normal waves Normal waves are caused by the wind pushing the water.

The stronger the wind blows, the bigger the waves. wind

wind wind

tiny ripples

ripple

Waves are also created as tides slowly pull the ocean inland and away again every day. high tide

choppy sea

waves break

Fact Tides are caused by the pull of the moon and sun on the earth. low tide

4

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Tsunami waves Tsunami waves are different to normal waves in several ways. Tsunamis are much faster out at sea; they can travel over 800 kilometres per hour. They also have a longer period – there can be two hours between each wave.

Typical tsunami wave versus normal wave normal wave

tsunami wave

wave speed

eight to 100 kilometres per hour

800 to 965 kilometres per hour

wave period

three to 20 seconds apart

ten minutes to two hours apart

wavelength

30 to 200 metres apart

100 to 500 kilometres apart

wave height

one to seven metres

three to ten metres

6

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