Divergent boundaries, where new crust is generated as the plates pull away from each other. Convergent boundaries, where crust is destroyed as one plate dives under another. Finally, there's Transform boundaries, where crust is neither produced nor destroyed as the plates slide horizontally past each other. Divergent Boundaries create mountain ranges, as the plates pull apart and magma from Earth's core rises through the gap and flows out. It then cools, and over millions of years, this process builds until the magma has risen up so far it is a mountain
