Catastrophic Events

Part II

Lesson 14: Using Earthquakes to Study the Earth’s Interior

Focus Question: How is the interior of the Earth arranged?

Learning Targets:

  • I understand earthquake waves help scientists to construct hypotheses about the structure of the earth’s interior.
  • I understand the earth has layers, including a crust, a mantle, and a core; the core is divided into a liquid outer core and a solid inner core.
  • I understand the crust and rigid portion of the upper mantle make up the lithosphere, which is broken into plates that move over a plastic-like portion of the mantle.
  • I understand lithospheric plates move at a rate of 2 to 20 cm per year.
  • I understand major geological events, such as earthquakes, volcanoes, and mountain building, can result from plate movement.

Student Objectives:

  • Examine the interior structure of some common objects.
  • Discuss how scientists study the structure of the earth’s interior.
  • Recognize that an understanding of the motion of earthquake waves can help scientists formulate hypotheses about the earth’s interior.
  • Using computer images identify and describe the layers of the earth.
  • Plot the locations of volcanoes and compare these with those of earthquakes.

Getting Started:

  1. Share your homework with the class. Consider the following questions:
  2. How did you discover the internal structure of the object you chose?
  3. How does the structure of this object compare with that of objects other students brought to class?
  4. How did you use diagrams and labels to show the structure of the object you chose?
  1. Look closely at the items your teacher shows you. With your group, discuss each object. These questions will guide you.
  2. What do you think each item looks like inside?
  3. How could you find out about the interior structure of each item?
  1. Watch as your teacher cuts open each item. Compare the objects. How are they alike? How are they different?
  2. Share what you already know and what you want to know about the earth’s interior structure. Your teacher will record your ideas.
  3. Discuss these questions with the class.
  4. How do you think the structure of these items resembles the structure of the earth’s interior?
  5. How do you think scientists study and learn about the earth’s interior?

Inquiry 14.1: Examining the Earth’s Interior

  1. Think back to Lesson 11 and 12. How do you think scientists use earthquake waves to tell whether the interior of the earth is solid, liquid, or gas?
  2. Watch as your teacher creates waves in a plastic box filled with water. Then predict what might happen to the waves when a can is placed in the center of the plastic box. Discuss your prediction with the class. Next, watch as your teacher tests your prediction. Discuss your observations with the class.
  3. Look at the diagram of the earth’s interior on page 167. What can the motion of earthquake waves tell about the earth’s interior?
  4. Watch computer images of the earth’s interior on a CD-ROM.

Reflecting on What You’ve Done:

  1. As a class, answer the review questions from the CD-ROM.
  2. Read “The Earth’s Interior,” on page 167.
  3. Answer these questions in your notebook.
  4. Why are the images on the CD-ROM and in the reading selection drawings rather than photographs?
  5. Describe each layer of the earth.
  6. Read “Using Waves to Explore the Earth’s Interior,” on pages 168-169. How do earthquake waves help scientists learn more about the earth’s interior? Write down your ideas.
  7. For homework, you will be asked to complete Student Sheet 14.1: Plotting Volcanoes Activity to find out how the location of volcanoes and earthquakes are alike.
  8. Look ahead to Lessons 15 and 16, in which you will investigate the causes of earthquakes and volcanoes as they relate to plate movement.