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Earthquakes
Earthquakes are sudden, violent shifting movements in the
earth’s crust that can release more energy than a nuclear bomb.
During earthquakes, the land trembles and shakes, often violently
enough to topple buildings and collapse bridges. Sometimes the
land cracks open.
About 900 earthquakes occur every hour. Most of these are
very minor and probably can’t be felt by humans. Others destroy
whole cities and landscapes.
Seismologists, the scientists who study earthquakes, use a
scale to describe their force, or intensity. This scale is known as
the Richter scale. The scale was devised by Charles Richter and
Beno Gutenberg. It measures earthquakes on a scale of 1 to 10,
with 1 being the least powerful and 10 the most powerful.
Earthquakes are caused when the tectonic plates that make
up the earth’s surface collide, separate, or scrape against each
other. Because one plate can move faster or in a different direction
than another, the plates do not always slip smoothly past each
other. When that happens, the earth’s surface jerks and shifts along
the plate boundaries. These boundaries are called fault lines. But
not all fault lines are located on plate boundaries.
Most earthquakes - eighty percent - as well as volcanic
eruptions occur in the Ring of Fire, a narrow band of land on the
edges of the Pacific Plate.
Comprehension Questions

I. Say which of the following statements are false and
which are true. Correct the false statements to make them
true.
1. Sudden, violent shifting movements in the earth’s crust
are called earthquakes.
2. Earthquakes can release less energy than a nuclear
bomb.
3. During earthquakes the land never cracks open.
4. Seismologists are the scientists who study earthquakes.
5. Earthquakes are caused when the tectonic plates that
make up the earth’s surface collide, separate, or scrape
against each other.

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