There are three kinds of plate tectonic boundaries: divergent, convergent and transform plate boundaries. Convergent – plates move toward one another. Divergent – plates move away from each other. Transform – plate moves sideways from each other. Oceanic plates: basalt. Dark (black) and dense rock type composed of silicates, iron and magnesium. Continental plates – granite and andesite. Light colored (pink, white and gray) and low density rock type composed almost entirely of silicates.