Transcript Geography Earth Forces

Geography
Earth Forces
Earthquakes
[Date]
Today I will:
- Know what an earthquake is.
- Know how the strength of an earthquake is measured.
Geography
Earth Forces
Earthquakes are the shaking of the Earth’s surface. They are
caused by the sudden movement of tectonic plates.
Most earthquakes only last a matter of seconds!
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Earthquakes occur when rocks inside the crust move suddenly.
This sudden movement causes shock waves to travel out in all
directions.
There are 3 types of shock waves:
- P Waves (Push/Primary) make the
rocks move up and down – the fastest
waves.
- S Waves (Shake/Secondary) make
rocks move from side to side.
- L Waves (Long) spread out along
the surface – slowest but most
destructive.
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The intensity of
earthquakes are
measured with a
‘Seismometer’.
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And these
results are
shown on a
seismograph
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Earthquakes can cause a
lot of destruction and
even start fires.
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