Volcanoes Across 8. Where volcanoes form Down 1. Tube in the middle of a volcano 2. Lava which flows down the side of the volcano 3. Lumps of molten rock thrown up by the volcano 4. When volcanoes explode it is called an... 5. The opening at the top of a volcano 6. Where molten rock is stored inside the earth's crust 7. Form if the main vent is blocked