| A | B |
|---|
| igneous rocks | most abundant on Earth |
| magma | igneous rock - subsurface melt |
| lava | igneous rock - melts at the surface |
| intrusive igneous rocks | cool slowly underground |
| extrusive igneous rocks | cool quickly at the surface |
| lava | cooled liquid melts at surface |
| pyroclastic debris | cooled fragments (ash and fragmented lava) |
| Two types of magma | felsic and mafic (based on percent of silica) |
| felsic | 66-76% silica |
| mafic | 45-52% silica |
| viscosity | resistance to flow |
| higher vicosity | slower flow |
| higher silica content | higher viscosity |
| higher temperatures | lower viscosity |
| higher gas content | lower viscosity |
| magma formation | see diagram |
| volatiles | cause rocks to melt at much lower temperature (add volatile to hot dry rocks and melting begins) |
| eutectic temperature | temperature that rocks begin to melt |
| fractionation | melt separated from solid material during melting |
| magma moves ? | upward, it is less dense than rock |
| How does magma move? | injected into cracks, melting overlying rocks, squeezed by overburden |
| what are the two igneous environments? | extrusive and intrusive |
| extrusive | cool at or near the surface |
| intrusive | cool at depth |
| characteristics of extrusive | lava flows, lava cools and solidifes as flowing |
| extrusive characteristics | ash eruptions |
| intrusive characteristics | intrudes into rocks in 2 ways (dikes and sill OR plutons) |
| types of intrusions | sill and dike |
| sill | parallels rock fabric |
| dike | crosscuts rock fabric |
