| A | B |
|---|
| volcano | weak spot in the crust where molten material comes to the surface |
| magma | molten mixture of rock-forming substances gases and water from the mantle |
| lava | magma that reaches the surface |
| Ring of Fire | a major volcanic belt that is formed by the many volcanoes that rim the Pacific Ocean |
| island arc | string of islands formed by the volcanoes along a deep ocean trench |
| hot spot | area where magma from deep within the mantle melts through the crust like a blow torch |
| magma chamber | an area beaneath a volcano where magma collects |
| pipe | long tube in the ground that connects the magma chamber to the earth's surface |
| vent | opening where molten rock and gas leave the volcano |
| lava flow | area covered by lava as it pours out of a vent |
| crater | bowl shaped area that may form at the top of a volcano around the central vent |
| silica | material that is formed from the elements oxygen and silicon |
| Pahoehoe | fast moving, hot lava |
| aa | cooler, slower moving lava |
| pyroclastic flow | when an explosive eruption hurls out ash, cinders, bombs as well as gases |
| active volcano | a volcano that is erupting or has shown signs that it may erupt in the near future |
| dormant volcano | a sleeping volcano that may awaken in the near future and erupt |
| extinct volcano | a volcano that is unlikely to erupt again |
| hot spring | groundwater heated when a nearby body of magma rises to the surface and collects in a natural pool |
| geyser | fountain of water and steam that erupts from the ground |
| geothermal energy | water heated by magma that can provide a clean reliable energy source |
| shield volcano | a volcano formed by repeated lava flows during quiet eruptions, broad gently sloping shape |
| cinder cone volcano | steep cone shaped hill or mountain formed when cinders erupt explosively from a volcanic vent |
| composite volcano | tall cone shaped mountains in which layers of lava flow alternate with ash, cinder and bombs |
| caldera | huge hole left by the collapse of a volcanic mountain |
| volcanic neck | forms when magma hardens in a volcanic pipe |
| dike | magma that forces itself across rock layers |
| sill | magma squeezes between layers of rock |
| batholith | mass of rock formed when a large body of magma cools inside the crust |
