Discover the wonders of our earth with the Physical Geography DVD Series. This DVD looks at how earthquakes are measured. Seismologists from the National Earthquake Center in Golden, Colorado show how earthquake epicenters are located, and students will observe an actual earthquake being captured. The measurement scales, including both Mercalli and Richter, are explained. Subjects covered include: why earthquakes happen; where earthquakes occur around the world; what areas in the U.S. prone to earthquakes; how seismologists measure earthquakes; what happens when earthquakes occur under an ocean; historic earthquakes; and the difference between the Mercalli and Richter scales. Grades 9-12. 32 minutes on DVD.