Volcanoes, Earthquakes
and Floods

 Rapid changes to the earth's surface can occur during an earthquake, volcano or flood.

Directions:  Read the following paragraphs and choose the correct main idea for each paragraph.

1.  There are several events that can change the Earth's surface very quickly. Volcanoes can erupt and spread lava, rock and ash for several miles.  Earthquakes can leave large cracks in the Earth's surface.

        What is the main idea?

 

Several events can change the Earth's surface.

Earthquakes can cause large cracks. 

 Volcanoes can be dangerous.

2.  Most of the world's volcanoes are part of the "The Ring of Fire." This is a ring of volcanoes that form a circle around the Pacific Ocean. Thousands of volcanoes make up "The Ring of Fire." These volcanoes formed the sea floor and many underwater mountains.

What is the main idea?

There are thousands of volcanoes in the world.

Most volcanoes are part of the "Ring of Fire."

 Some underwater mountains are volcanoes.   


 

3. Earthquakes are caused when the plates of the Earth's crust move. Earthquakes happen along "fault lines" in the earthís crust. When the plates in the Earth suddenly shift, the Earth will begin to shift, shake or tremble.

What is the main idea?

Earthquakes occur on "fault lines."

Earthquakes cause a lot of damage.     

Earthquakes are caused when the plates of the Earth's crust
      move.


 

4. Scientists can measure the intensity of an earthquake. They use an instrument called the Richter scale. The Richter scale compares the strength of different earthquakes. Earthquakes  below 2.0 usually canít be felt. Earthquakes over 5.0 on the scale can cause damage. A magnitude 7.0 is a major earthquake and can cause tremendous damage.

What is the main idea?

Scientists can measure the intensity of an earthquake.

Strong earthquakes can cause lots of damage.

 Some earthquakes are very small. 

 

5.   Floods can cause tremendous damage.  They can ruin houses, roads and buildings. Floods can take down trees and cause mudslides. It often leaves mud, sand and debris behind.  It can take months to clean up after a flood.

What is the main idea?

Floods can cause a lot of damage.

Floods cause mudslides.

 Floods damage houses and roads.  

6.  The earth's surface is constantly changing.  All over the world everyday there are earthquakes, floods and volcanoes that quickly change our world. Some changes are too small to see.  Others cause tremendous damage and costs millions of dollars to clean up.

What is the main idea?

It is expensive to clean up the damage.

Sometimes we can't see the changes.     

The Earth's surface is always changing.

 

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