| A | B |
|---|
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, also the rock formed when liquid lava hardens. |
| Ring of Fire | A major belt of volcanoes that rims the Pacific Ocean. |
| island arc | A string of islands formed by the volcanoes along a deep ocean trench. |
| hot spot | An area where magma from deep within the mantle melts through the crust above it. |
| shield volcano | A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions. |
| cinder cone | A steep, cone-shaped hill or 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. |
| caldera | The large hole at the top of a volcano formed when the roof of a volcano's magma chamber collapses. |
| 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 cooled inside the crust. |
