Volcanoes form most commonly in regions where one tectonic plate plunges beneath another tectonic plate. how does this process lead to volcano formation? a. the plate plunging downward suddenly turns upward, busting through the surface to form volcanoes. b. the plate plunging downward knocks loose part of the earth's core, which rises up to form volcanoes at the surface. c. it causes part of the overriding plate to melt into magma, which rises up to form volcanoes at the surface.