| A | B |
|---|
| volcano | a weak spot in the crust where molten material, or magma, comes to the surface |
| magma | a molten mixture of rock-forming substances, gases, and water from the mantle |
| Ring of Fire | a major volcanic belt around the Pacific Ocean |
| island arc | a string of islands formed by the volcanoes along a deep-ocean trench |
| hot spot | an area where material from deep within the mantle rises and then melts, forming magma |
| magma chamber | a pocket beneath a volcano where magma collects |
| pipe | a long tube in the ground that connects the magma chamber to Earth's surface |
| vent | an opening in a volcano where molten rock and gas leave. |
| lava flow | the area covered by lava as it pours out of a vent |
| crater | a bowl-shaped area that may form at the top of a volcano around the central vent |
| silica | a material found in magma that is formed from the elements oxygen and silicon |
| magma | molten rock beneath the Earth's surface |
| lava | molten rock on the Earth's surface |
| pyroclastic flow | a type of explosive eruption that hurls out a mixture of hot gases, ash, cinders and bombs |
| dormant | a volcano that is not currently active, but that may become active in the future |
| extinct | a volcano that is unlikely to erupt again |
| geyser | a fountain of water and steam that erupts from the ground |
| volcanic bomb | particles from volcanic eruption larger than 5mm |
| cinder | small, rough volcanic bomb no more than several cm across |
| cinder cone | volcano made of cinders and rock particles that have been blown into the air |
| shield volcano | gently sloping volcano formed when runny lava flows over a large area |
| composite volcano | volcano built of alternating layers of rock particles and lava |
| caldera | a huge hole left by the collapse of a volcanic mountain |
| volcanic neck | hardened magma in a volcano's pipe |
| dike | a slab of volcanic rock formed when magma forces itself across rock layers |
| batholith | a mass of rock formed when a large body of magma cools inside the crust |
