This demonstration of plate tectonic principles, plate boundary interactions, and the geometry and relative motions of faulting of geologic layers uses 3-D foam models. The models aid in visualization and understanding of plate motions and faulting because they are three-dimensional, concrete rather than abstract descriptions or diagrams, can be manipulated by the instructor and the students, and can show the motions of the plates and faults through time in addition to the three-dimensional configuration of the plates or layers. The models illustrate relatively simple motions and geologic structures, including faulting and plate boundaries, compressional motion and resulting reverse (also called thrust) faults, horizontal slip or strike-slip fault motion, slip or strike-slip fault motion, transform or strike-slip plate boundaries, and elastic rebound.