Earthquakes are far too real a danger for many Americans today. In 2019 and 2020, Puerto Rico was hit by a string of earthquakes, the largest of which reached a magnitude of 6.4. These earthquakes killed people and left many more injured or homeless. They also caused several hundred million dollars in damages. This title looks at the science behind earthquakes and how and why they occur, as well as how scientists detect and measure them. Primary sources, charts, and graphic organizers provide additional information and help readers develop important critical-thinking skills.