| A | B |
|---|
| magma | molten rock below earth's surface |
| lava | molten rock above the earth's surface |
| volcano | opening in earth's crust through which molten rock moves. |
| felsic | molten rock high in silica and light in color |
| mafic | molten rock low in silica and dark in color |
| tephra | solid fragments from explosive eruptions |
| rift eruptions | occur at long narrow fractures in the crust |
| subduction boundary eruptions | magma here is thick and contains large amounts of gases which causes explosive eruptions |
| hot spots | areas of volcanic activity in the middle of lithospheric plates |
| plutons | form when magma cools inside other rocks |
| dikes | sheets of igneous rocks that cut across rock layers |
| sills | sheets of igneous rocks that run parallel to the layers they intrude |
| laccoliths | these magmas bulge upward to form domelike masses of rock |
| volcanic neck | leftover from the erosion of a volcanic cone |
| batholith | massive features which form the cores of many of earth's mountain ranges |
| stock | a small batholith; less than 100 square kilometers exposed at the surface |
| ash | volcanic powder |
| lapilli | volcanic pebbles, gravel sized |
| blocks | angular solid pieces |
| bombs | liquid mass which then cools to form a solid |
