| A | B |
|---|
| Volcano | Opening in Earth's surface that often forms a mountain when layers of lava and ash erupt and build up. |
| Vent | Opening on Earth's surface where magma is forced up and flows out as lava. |
| Crater | Steep-walled depression around a volcano's vent. |
| Hot Spot | Location in the mantle that is hotter than other areas and that melts rock, which is forced up toward the crust as magma. |
| Shield Volcano | Broad volcano with gently sloping sides formed when hot, fluid lava flows from one or more vents. |
| Tephra | Bits of rock or solidified lava dropped from the air during an explosive volcanic eruption. |
| Cinder Cone | Steep-sided volcano made of loosely packed tephra. |
| Composite Volcano | Volcano formed by alternating layers of tephra and lava and that is found mostly where Earth's plates come together. |
| Batholith | Largest intrusive igneous rock bodies that form when magma cools underground before reaching Earth's surface. |
| Dike | Intrusive igneous rock body formed when magma is squeezed into a vertical crack that cuts across rock layers and hardens. |
| Sill | Intrusive igneous rock body that forms when magma is squeezed into a horizontal crack between rock layers and hardens. |
| Volcanic Neck | Solid, igneous core of a volcano left behind when a volcano stops erupting and the softer cone erodes away. |
| Caldera | Large opening formed when the top of a volcano collapses. |
| Magma | Melted rock that is still beneath the Earth's surface. |
| Rifts | Long, deep cracks caused by the separation of Earth's plates. |
| Silica | A compound composied of the elements silicon and oxygen. |
