1. Igneous rocks found at convergent boundaries are typically mafic in composition. True False 2. Pyroclastic flows are _____ flows that are driven by ______. superheated; number of particles cold; gravity superheated; gravity cold; number of particles 3. How does convection cause the motion of plates that drives plate tectonics? Cold, dense lithosphere sinks, while hot, low-density mantle rises to the surface Convection blows the plates around the earth. Refraction of heat from the sun heats the plates, causing convection and the motion of the plates. Radiation of heat causes the plates to move, which in turn causes convection When an isotopes experiences radioactive decay it spins around creating convection cells..