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How Earthquakes Are Measured

7th grade nonfiction passage about earthquakes: 271 words, seven questions, an answer key and vocabulary.

7th grade nonfiction earthquakes 271 words

How Earthquakes Are Measured

An earthquake begins deep underground when blocks of rock that have been pressing against each other suddenly slip. The slip sends out waves of energy, called seismic waves, that travel through the planet in every direction. When those waves reach the surface, the ground shakes.

Scientists record this shaking with an instrument called a seismograph. The main part of a seismograph is a heavy weight hanging from a frame. When the ground moves, the frame moves with it, but the weight stays almost still because of its inertia. A pen or a sensor records the difference between the two, and the result is a wiggly line that shows how strong the shaking was.

Seismic waves come in different types that travel at different speeds. The fastest, called P waves, arrive first. The slower S waves arrive a little later. By measuring the gap between the two, a scientist can work out how far away the earthquake was. Readings from at least three stations in different places can then be combined to pinpoint the epicenter, the spot on the surface directly above where the rock slipped.

To describe the size of an earthquake, scientists use a number called magnitude. In 1935, an American scientist named Charles Richter created the first widely used scale. Today most experts use a newer method, the moment magnitude scale, which works better for very large earthquakes. On both scales, each step up of one whole number means the ground moves about ten times more.

Thousands of earthquakes happen every day, but nearly all are too small for anyone to feel. Measuring them carefully helps engineers design safer buildings.

Questions

  1. What causes an earthquake to begin? in the text

  2. What instrument do scientists use to record shaking? in the text

  3. Which waves arrive first, P waves or S waves? in the text

  4. What is the epicenter? in the text

  5. What does each step up of one whole number on the scale mean? in the text

  6. Why does the weight in a seismograph stay almost still when the ground moves? think about it

  7. How can the gap between P waves and S waves tell a scientist something? think about it

Words to know

seismic
having to do with earthquakes
seismograph
an instrument that records the shaking of the ground
inertia
the tendency of an object to keep still or keep moving
epicenter
the spot on the surface above where an earthquake begins
magnitude
a number that tells how big an earthquake is
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 254 words · Flesch-Kincaid grade 4.6

An earthquake starts deep underground. Blocks of rock have been pressing on each other, and then they slip. The slip sends out waves of energy. These are called seismic waves. They travel through the planet in every direction. When they reach the surface, the ground shakes.

Scientists record the shaking with a seismograph. It has a heavy weight that hangs from a frame. When the ground moves, the frame moves too. But the weight stays almost still, because of its inertia. A pen or a sensor records the difference. The result is a wiggly line that shows how strong the shaking was.

Seismic waves come in types, and they travel at different speeds. The fastest are P waves. They arrive first. The slower S waves arrive a bit later. A scientist can measure the gap between them to find out how far away the earthquake was. Readings from three or more stations can be put together to find the epicenter. This is the spot on the surface right above where the rock slipped.

To tell how big an earthquake is, scientists use a number called magnitude. In 1935, an American scientist named Charles Richter made the first scale that many people used. Today most experts use a newer one, the moment magnitude scale. It works better for very large earthquakes. On both scales, one whole number up means the ground moves about ten times more.

Thousands of earthquakes happen every day. Nearly all are too small to feel. Measuring them helps engineers build safer buildings.

▲ This passage · 271 words · Flesch-Kincaid grade 7.7

An earthquake begins deep underground when blocks of rock that have been pressing against each other suddenly slip. The slip sends out waves of energy, called seismic waves, that travel through the planet in every direction. When those waves reach the surface, the ground shakes.

Scientists record this shaking with an instrument called a seismograph. The main part of a seismograph is a heavy weight hanging from a frame. When the ground moves, the frame moves with it, but the weight stays almost still because of its inertia. A pen or a sensor records the difference between the two, and the result is a wiggly line that shows how strong the shaking was.

Seismic waves come in different types that travel at different speeds. The fastest, called P waves, arrive first. The slower S waves arrive a little later. By measuring the gap between the two, a scientist can work out how far away the earthquake was. Readings from at least three stations in different places can then be combined to pinpoint the epicenter, the spot on the surface directly above where the rock slipped.

To describe the size of an earthquake, scientists use a number called magnitude. In 1935, an American scientist named Charles Richter created the first widely used scale. Today most experts use a newer method, the moment magnitude scale, which works better for very large earthquakes. On both scales, each step up of one whole number means the ground moves about ten times more.

Thousands of earthquakes happen every day, but nearly all are too small for anyone to feel. Measuring them carefully helps engineers design safer buildings.

■ Harder · 293 words · Flesch-Kincaid grade 10.8

An earthquake originates deep beneath the surface when blocks of rock that have been pressing against one another with tremendous force suddenly slip. The slippage releases waves of energy, known as seismic waves, which radiate through the planet in every direction, and when those waves finally reach the surface, the ground begins to shake violently enough to be felt.

Scientists document this shaking with an instrument called a seismograph. Its central component is a heavy weight suspended from a frame. When the ground moves, the frame moves along with it, yet the weight remains nearly motionless because of its inertia. A pen or an electronic sensor records the difference between the two, producing a wavering line that reveals how powerful the shaking was.

Seismic waves come in several varieties that travel at different speeds. The swiftest, called P waves, arrive first, while the slower S waves follow a little later. By measuring the interval between the two, a scientist can calculate how far away the earthquake occurred. Readings gathered from at least three stations in different locations can then be combined to pinpoint the epicenter, which is the spot on the surface directly above the place where the rock slipped.

To describe the size of an earthquake, scientists rely on a number called magnitude. In 1935, an American scientist named Charles Richter devised the first widely adopted scale. Today most experts prefer a newer approach, the moment magnitude scale, which is more reliable for extremely large earthquakes. On both scales, each step upward by one whole number indicates that the ground moves roughly ten times more.

Thousands of earthquakes occur every day, but nearly all are far too weak for anyone to notice. Measuring them carefully helps engineers design buildings that are considerably safer.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put seismic, seismograph, inertia, epicenter and magnitude on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 6 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "How Earthquakes Are Measured"?

It was written for 7th grade. It has 271 words and works out to a Flesch-Kincaid grade level of about 7.7. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are seven. 5 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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