Volcanoes and Plate Tectonics are more similar than you and I might think. Plate Tectonics are are the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle, and a volcano usually rises on a border of a Plate tectonic. (Hint: The ring of fire) Volcanoes are weak spots in the Earth's crust where magma has come to the surface and is about to erupt. When Plate Tectonics shift in convergent, or divergent ways volcanoes can also form because of the movement in the crust. The ring of fire as shown in the picture below is right along the pacific and North American Plate boundaries which then triggers over 50 eruptions each year because of the shifting of the plates.