Earthquakes,also called temblors (地震) ,can be so extremely destructive; it's hard to imagine they occur by the thousands every day around the world,usually in the form of small tremors.

Some 80 per cent of all the planet's earthquakes occur along the rim of the Pacific Ocean,called the "Ring of Fire" because of the preponderance (数量上的优势) of volcanic activity there as well. Most earthquakes occur at fault zones,where tectonic plates―giant rock slabs that make up the earth's upper lay?er―crash or slide against each other. These impacts are usually gradual and unnoticeable on the surface. However,immense stress can build up between plates. When this stress is released quickly,it sends massive vibrations (震动) ,called seis?mic waves,often hundreds of miles through the rock and up to the surface. Other quakes can occur far from fault zones when plates are stretched or squeezed.

Scientists assign a magnitude rating to earthquakes based on the strength and du?ration of their seismic waves. A quake measuring 3  to 5 is considered minor or light; 5 to 7  is moderate to strong; 7 to 8  is major,and 8 or more is great.

On average,a magnitude 8  quake strikes somewhere every year and some 10,000 people die worldwide annually in earthquakes. Collapsing buildings claim by far the majority of lives,but the destruction is often compounded (加重) by mud slides,fires,floods,or tsunamis. Smaller temblors that usually occur in the days following a large earthquake can complicate rescue efforts and cause further death and destruction.

Loss of life can be avoided through emergency planning,education,and the construction of buildings that sway rather than break under the stress of an earth?quake.

1. Why is the rim of the Pacific Ocean called the "Ring of Fire"?

   A. Because 80 %of the earth's quakes occur there.

   B. Because there are many fault zones along the rim.

   C. Because volcanoes happen actively along the rim.

   D. Because seismic waves are sent out from the rim.

2. An earthquake can't happen when         .

   A. tectonic plates collide against each other

   B. tectonic plates are stretched

   C. tectonic plates move slightly

   D. tectonic plates are squeezed

3. A major earthquake is measured at a magnitude of         .

   A. 7 to 8     B. 5 to 7

   C. 3 to 5     D. 8 or more

4. What is the most effective way to avoid death in earthquakes?

   A. To make quick rescue efforts.

   B. To educate people knowledge of earthquakes.

   C. To have a detailed plan in an emergency.

   D. To build buildings strong enough.

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