| Question | Answer |
| 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 | 1. a large round pit caused by the impact of a meteoroid 2. 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 | 1. term used to refer to a group of related organisms that has died out and has no living members 2. Term used to describe a volcano that is no longer active and unlikely to erupt again |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 |
