| A | B |
|---|
| Volcano | An opening in Earth’s surface that erupts sulfurous gases, ash, and lava; can form at Earth’s plate boundaries, where plates move apart or together, and at hot spots |
| Vent | An opening on a volcano where magma is forced up and flows out onto Earth’s surface as lava |
| Crater | A steep-walled depression around a volcano’s vent |
| Hot spot | The result of an unusually hot area at the boundary between Earth’s mantle and core that forms volcanoes when melted rock is forced upward and breaks through the crust |
| Shield volcano | A broad, gently sloping volcano formed by quiet eruptions of basaltic lava |
| Tephra | Bits of rock or solidified lava dropped from the air during an explosive volcanic eruption; ranges in size from volcanic ash to volcanic bombs and blocks |
| Cinder cone volcano | A steep-sided, loosely packed volcano formed when tephra falls to the ground |
| Composite volcano | A volcano built by alternating explosive and quiet eruptions that produce layers of tephra and lava |
| Batholith | The largest intrusive igneous rock body that forms when magma being forced upward toward Earth’s crust cools slowly and solidifies underground |
| Dike | Igneous rock feature formed when magma is squeezed into a vertical crack that cuts across rock layers and hardens underground |
| Sill | Igneous rock feature formed when magma is squeezed into a horizontal crack between layers of rock and hardens underground |
| Volcanic neck | The solid igneous core of a volcano left behind after the softer cone has been eroded |
| Caldera | The large, circular-shaped opening formed when the top of a volcano collapses |
