| 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 |
| Lava | Magma that reaches the surface |
| Ring of Fire | The volcanic belt that circles the Pacific Ocean |
| Island arc | Strings of islands created by underwater volcanoes |
| Hot spot | An area where material from deep within the mantle rises and melts forming magma |
| Element | A substance that can't be broken down into other substances |
| Compound | A substance made of two or more elements that have been chemically combined |
| Viscosity | The resistance of liquid to flowing |
| Pahoehoe | Fast-moving, hot lava that has low viscosity |
| Pyroclastic flow | An explosive eruption hurls out a mixture of hot gases, ash, cinders, and bombs |
| Dormant | A volcano that is expected to awaken in the future and become active |
| Active | A volcano that currently erupts |
| Extinct | A volcano that is not expected to become active again |
| Caldera | A huge hole left behind by the collapse of a volcanic mountain |
| Sill | When magma squeezes between horizontal layers of rock |
| Geothermal activity | Magma beneath Earth's surface heats underground water |
| Geyser | A fountain of water and steam that erupts from the ground |
