Lesson 2: Volcano Risks - Dutch learned that volcanic eruptions change Earth’s surface and they form along convergent boundaries. Then he discovered that landforms called volcanoes form when molten rock erupts onto Earth’s surface. Next we learned that volcanoes occur at divergent and convergent plate boundaries. At a divergent boundary lava flows into the rift created by the separating plates. This lava forms oceanic crust as a cools. Mid-ocean ridges are underwater mountains that form as lava cools and builds up. He learned that sometimes a tectonic plate at a convergent boundary will sink into the mantle carrying water with it and causing the mantle to melt and form magma. Some large volcanoes form at hot spots which are locations where volcanoes form far from plate boundaries. In order for magma to form, the crust and mantle must become hot enough to melt.