| A | B |
|---|
| ash | lava fragments less than 0.5 cm across |
| basalt | very dense, dark grey fine-grained igneous rock |
| bomb | Fragment of magma varying in diameter from a few inches to several feet |
| caldera | crater > 1 mi. in diameter formed by the collapse of a volcano summit |
| cinder | volcano cone built of frothy, irregular lava fragments |
| stratovolcano | characterized by a steep profile and periodic, explosive eruptions |
| crater | depression often found at the top of a volcanic cone |
| fissure | long narrow slit or groove |
| fumarole | hole or spot in a volcano that releases gases |
| geyser | A spring that discharges hot water and steam |
| hotspot | area in mantle that contains large magma chamber that burns hole through the crust |
| lahar | avalanche of volcanic water and mud down the slopes of a volcano |
| lapilli | volcanic particles that range in size from 2 mm to 64 mm in diameter |
| lava | magma when it reaches the surface |
| magma | Molten rock in the earth's crust |
| pyroclastic | fast, hot flows formed by the fallback of volcanic ash clouds that originally jetted upward |
| shield | a broad fairly flat volcano having the shape of a shield |
| tephra | solid material thrown into the air by a volcanic eruption that settles on the surrounding areas |
| dormant | volcano that has been inactive for an extended period of time |
| pahoehoe | smooth and fast flowing lava |
| aa | lava that has a rough surface and irregularly shaped holes in it |
| pumice | extremely light form of cinder, formed when lots of dissolved gas bubbles out of lava |
| volcanologist | scientist who studies volcanoes. |
