I use these sites in the computer lab to allow my students to explore the different levels of earthquake intensity or the different types of volcanic eruptions. They can play "Mother Nature" by adjusting earthquake parameters, such as ground foundation type, prevention methods, and magnitude. The earthquake is started, and they see the damage that can occur to a building that is on the screen. It also mentions possible death tolls, possible injuries, dollar damage, etc. With the volcano exercise, they can adjust parameters, such as lava viscosity and gas pressure. The site mentions the type of volcano or volcanic feature that the set conditions favor. The students cause the volcano to erupt, and they see the type of eruption, damages, etc...sound effects and all. These are terrific sites that really engage the students.
Virtual Earthquake exercise: http://tlc.discovery.com/convergence/quakes/interactives/makeaquake.html
Virtual Volcano exercise: