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4. Earthquakes

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About one million earthquakes happen every year

Vocabulary

earthquake

A shaking of the surface of Earth when the plates of Earth

move

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Most earthquakes happen under the ocean or are too

small to notice

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In a strong earthquake the ground can shake violently and

even split open

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Most earthquakes are caused by the sudden movement of

plates along a fault

Remember: a fault is the place where two plates meet

Romania Jan 30 2000

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When the plates move, the crust near the fault is squeezed

and stretched

Rocks in the crust break and move apart at a point called

the focus

Click image for focus points

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Vocabulary

focus

The point where rocks in the crust break and move apart

during an earthquake

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The focus is usually less than 25 miles below the surface of

Earth

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Near epicenter of an earthquake is where the most

damage occurs Vocabulary:

epicenter

The place on the surface of Earth directly above the focus

of an earthquake

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If the focus of an earthquake is under the ocean floor, a

tsunami is producedVocabulary:

tsunami

A giant wave produced when the focus of an earthquake is

under the ocean floor

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This huge wall of water moves across the ocean at high speed

It causes great damage when it reaches land

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Many earthquakes take place in an area known as the

Ring of Fire

Volcanoes are also common in this area

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This chain of earthquake zones and volcanoes circles the

Pacific Plate

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