| A | B |
|---|
| volcano | any opening in Earth's crust through which hot gases, rocks, and melted material erupt |
| magma | hot, melted rock |
| lava | magma that reaches the Earth's surface |
| cinder cone | steep slopes, explosive eruptions |
| shield cones | large, gentle slopes; gentle eruptions |
| composite cones | eruption alternates between gentle and explosive eruptions |
| island arc | a chain of volcanoes formed from magma that rises as a result of an oceanic plate sinking into the mantle |
| seisometer | an instrument that detects Earth's movements |
| tiltmeter | measures any change in the slope of an area |
| hot spots | extremely hot places deep within Earth's mantle |
| caldera | large, circular depression at the top of a volcano |
| rifting | process that occurs at divergent plate bounderies |
