The Earth's crust is not one solid piece of rock. It is broken up into several larger and smaller tectonic plates. The tectonic plates move in specific directions as a result of convection currents in the mantle. Geographer Dan Raven-Ellison demonstrates the movement of the earth’s crust explaining how tectonic plates interact at plate boundaries. Through the use of animated hand-drawn diagrams, Dan is able to show the movement at different plate boundaries.