| A | B |
|---|
| Volcano | A weak spot in the Earths crust where lava has come to the surface. |
| Ring of Fire | A major belt of volcanoes that rims the Pacific Ocean along plate boundaries. |
| Magma | The molten mixture of rock-forming minerals, gases, water, and other substances that makes up part of Earths mantle. |
| Lava | Magma that reaches the surface; also the rock formed when liquid lava hardens. |
| Island arc | A string of islands formed by the volcanoes along a deep ocean trench where subduction is occurring. |
| Hot spot | An area where magma from deep within the mantle rises and melts through the crust above it. |
| Magma chamber | The large pocket beneath a volcano that holds the magma that has traveled upward from the mantle. |
| Pipe | A long tube through which magma moves from the magma chamber to Earths surface. |
| Vent | The opening through molten lava and gas leave a volcano. |
| Lava flow | The area covered by lava as it pours out of a volcanoes vent. |
| Crater | A bowl-shaped area that forms around a volcanos central opening. |
| Silica | A material that is formed from the elements oxygen and silicon; the amount of silica determines the viscosity of magma |
| Viscosity | The tendency of liquids to resist flowing; the viscosity of magma determines the volcanos eruption style and its shape. |
| Pahoehoe | A hot, fast moving type of lava that hardens to form smooth, rope like coils. |
| Aa | A slow-moving type of basaltic lava that hardens to form rough chunks; cooler than pahoehoe. |
| Pyroclastic flow | The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption. |
| Active | A classification of a volcano that is erupting or has shown signs of erupting in the near future. |
| Dormant | A classification of a volcano that does not show signs of erupting in the near future. |
| Extinct | A classification of a volcano that is unlikely to erupt again |
| Hot spring | A pool formed by groundwater that has risen to the surface after being heated by a nearby body of magma. |
| Geyser | A type of hotspring that builds up pressure underground and erupts at regular intervals as a fountain of water and steam. |
| Geothermal energy | Heat energy in Earths interior from water or steam that has been heated by magma. |
| Shield volcano | A wide, gently sloping mountain made of layers of lava and formed by low silica, quiet eruptions. |
| Cinder cone | A steep, cone shaped hill or mountain made of volcanic ash, cinders, and bombs piled up around a volcanos opening. |
| Composite volcano | A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials. This type of volcano is said to have alternating violent and quiet eruption styles. |
| Caldera | The large hole at the top of a volcano formed when the roof of a volcanos magma chamber collapses. |
| Volcanic neck | A deposit of hardened magma in a volcanos pipe. |
| Dike | A slab of volcanic rock formed when magma forces itself across rock layers, usually at an angle. |
| Sill | A slab of volcanic rock formed when magma squeezes horizontally between layers of rock. |
| Batholith | A massive area of rock formed when a large body of magma cooled inside the crust. |
