| A | B |
|---|
| Volcano | A weak spot in the crust where magma has come to the surface. |
| Magma | The molten mixture of rock-forming substances, gases, and water from the mantle. |
| Lava | Liquid magma that reaches the surface. |
| Ring of Fire | A major belt of volcanoes that rims the Pacific Ocean. |
| Island Arc | A string of volcanoes that form as the result of subduction of one oceanic plate beneath a second oceanic plate. |
| Hot Spot | An area where magma from deep within the mantle melts through the crust above it. |
| Magma Chamber | The pocket beneath a volcano where magma collects. |
| Pipe | A long tube through which magma moves from the magma chamber to Earth’s surface. |
| Vent | The opening through which molten rock and gas leave a volcano. |
| Lava Flow | The area covered by lava as it pours out of a volcano’s vent. |
| Crater | A bowl-shaped area that forms around a volcano’s central opening. |
| Silica | A material found in magma that is formed from the elements oxygen and silicon; it is the primary substance of Earth’s crust and mantle. |
| Pyroclastic Flow | The flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption. |
| Dormant | Not currently active but able to become active in the future (as with a volcano) |
| Extinct | Term used to describe a volcano that is no longer active and is unlikely to erupt again. |
| Caldera | The large hole at the top of a volcano formed when the roof of a volcano’s magma chamber collapses. |
| Cinder Cone | A steep, cone-shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano’s opening. |
| Composite Volcano | A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials. |
| Shield Volcano | A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions. |
| Volcanic Neck | A deposit of hardened magma in a volcano’s pipe. |
| Dike | A slab of volcanic rock formed when magma forces itself across rock layers. |
| Sill | A slab of volcanic rock formed when magma squeezes between layers of rock. |
| Batholith | A mass of rock formed when a large body of magma cools inside the crust. |
