What geologic forces shaped southern Idaho? What is the Mantle Plume Theory? Objective Students will be able to explain the basics of the mantle plume theory. Students will understand that the crust slides over the mantle. Students will be able to name key cities and geologic features of Idaho. Background Students learn about the Mantle Plume Theory, plate tectonics, and Idaho geography by experimenting with a map of Idaho. (CLASSROOM ACTIVITY) The theory of plate tectonics explains much of Earth's geology. For example, California's famous San Andreas fault is formed where two tectonic plates Duration: 90 Minutes.