Conveying the dynamism of various geologic processes can be hard in the classroom or on the web, but this interactive feature from the Annenberg Media's Learner.org site does quite a fine job of introducing students to plate tectonics, plate boundaries, and such perennial favorites as earthquakes and volcanoes. In the "Earth's Structure" section, visitors can roll the mouse over such features as the crust, the mantle, and the outer core of the Earth to learn about each feature. Moving on, the "Plate Tectonics" area includes the "Continents Over Time" interactive feature which asks visitors to place images of the continents in the correct geologic order. Perhaps the most dynamic area of the site (with good reason) is the "Slip, Slide & Collide" area. Here visitors will learn about what happens at different types of plate boundaries through the use of colorful graphics and explanations that are easy to understand. Overall, the site is a great overview of some basic principles of geology, and one that can be used with students of different ages.