Ch 21: Earthquakes

About This Chapter

Watch online video lessons and learn what earthquakes are, what their impact can be, and how they are studied. These engaging lessons are just a portion of our online study guide and video collection. Each lesson is accompanied by a short quiz to challenge and help assess what you have learned.

Earthquakes - Chapter Summary and Learning Objectives

Earthquakes are the often catastrophic results of the rapid release of elastic energy stored in rocks. In this chapter, our knowledgeable instructors explain the causes of earthquakes and the terms used to describe their various aspects. You will learn about the damage earthquakes can cause and examine the technologies scientists use to study them. By the time you've finished the videos in this chapter, you will be familiar with:

  • The definition, causes, and history of earthquakes
  • Aftershocks and foreshocks
  • Scientific methods of studying and measuring earthquakes
  • Destruction caused by earthquakes
  • The source of earthquakes

Video Objective
What is an Earthquake? - Definition and History Describe the nature of earthquakes and define faults, foci, and epicenter.
The Causes of Earthquakes Learn how the rapid release of energy stored in rocks causes earthquakes and explain elastic rebound.
Aftershocks and Foreshocks of an Earthquake Examine the difference between aftershocks and foreshocks.
Using Seismic Waves Describe how seismic waves are used to study earthquakes.
Using the Richter Scale Explore how scientists use Richter Scale as a method of measuring earthquakes.
Destruction Caused by Earthquakes Study the nature of the damage caused by earthquakes.
Identifying the Source Research how the source of an earthquake is identified.

6 Lessons in Chapter 21: Earthquakes
Test your knowledge with a 30-question chapter practice test
What is an Earthquake? - Definition and Components

1. What is an Earthquake? - Definition and Components

When tensional stress caused by constantly shifting tectonic plates builds up enough energy, it results in an earthquake. Learn more about the definition of earthquakes and explore its components, such as faults, foreshocks and aftershocks, the focus or point at which rock breaks below the surface, and the epicenter.

The Causes of Earthquakes

2. The Causes of Earthquakes

Earthquakes can be detrimental natural disasters. Learn how tectonic plates make the ground shake through faults, and discover how the elastic rebound theory is correlated with the Earth's motion.

Identifying and Understanding Earthquakes Using Seismic Activity

3. Identifying and Understanding Earthquakes Using Seismic Activity

Learn about the importance of identifying and understanding earthquakes using seismic activity. Review seismographs and the different types of waves, including body waves vs. surface waves.

Aftershocks & Foreshocks of an Earthquake

4. Aftershocks & Foreshocks of an Earthquake

When rock below the Earth's surface breaks, it produces a large burst of energy called an earthquake. Earthquakes have foreshocks before they arrive, and aftershocks after they are gone. Investigate the foreshocks and aftershocks of an earthquake, and how they pertain to seismic activity.

Using the Richter Scale to Measure Earthquakes

5. Using the Richter Scale to Measure Earthquakes

The Richter scale measures the magnitude of earthquakes by calculating seismic data (vibrations beneath the Earth's crust) and energy expended. Explore how the Richter scale measures ground shaking as well as the use of the moment magnitude scale.

Destruction Caused by Earthquakes

6. Destruction Caused by Earthquakes

Earthquakes cause severe destruction and damage to the land and infrastructure. Explore the types of destruction and damage caused by earthquakes: physical land destruction, destruction near and at sea, structural damage, and economic damage.

Chapter Practice Exam
Test your knowledge of this chapter with a 30 question practice chapter exam.
Not Taken
Practice Final Exam
Test your knowledge of the entire course with a 50 question practice final exam.
Not Taken

Earning College Credit

Did you know… We have over 220 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.