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How Earthquakes Happen?

Would you be frightened if the ground started shaking under your feet?

Sudden, violent movements under the earth's surface are called earthquakes. 

Sometimes, the ground shakes so hard that buildings fall, roads and bridges are smashed and electric power lines break.
Look at this map of the world. The thick, black lines show the edges of the huge sections, or tectonic plates, in the earth's crust.
The shaded areas show places where earthquakes are strongest and happen most often. Most earthquakes occur near the edges of the plates.
Some of the earthquake areas, or zones, are on the land, and some are under the sea.

At the edges of the plates, there are cracks, or faults, in the earth's crust. Over many years, the plates slide past each other slowly, but sometimes the rocks get stuck together. Then the intense heat from inside the earth goes on pushing at them until they bend. Eventually, the pressure suddenly jolts them free, sending shock waves through the ground.

Earthquakes under the sea sometimes make giant ocean waves, called tsunamis. These destructive waves can be as high as 100 feet (30 meters), and happen most often in the Pacific Ocean, near Japan.

How we Measure earthquakes?

Scientists measure the strength of an earthquake in two different ways.
Using a measure called the Richter Scale, they measure the amount of energy that an earthquake releases and give it a score from 0 to 9. An earthquake that measures 9 is one billion times stronger than one that measures 1.

The Mercalli Scale measures the amount of damage an earthquake causes, and gives the damage a score from 1 to 12. A score of 1 means no damage, but a score of 12 means the earthquake has destroyed whole buildings.

It's a Fact

Every two or three minutes there’s an earthquake somewhere in the world.
The earth is always shivering! 

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