| A | B |
|---|
| Magma | a hot, partially molten, mobile material within the Earth that is capable of penetrating into or through rocks of the crust |
| Influence magma viscosity | SiO2 and water |
| Principle Elements of Magma | O, Si, Al, Ca, Na, K, Fe, and Mg |
| Lava | magma at the surface |
| Viscosity | resistance to flow |
| Felsic magma/lava | silica rich, thick viscous and resist flow |
| Mafic magma/lava | silica poor, thinner and have a lower viscosity and less resistant to flow |
| Controls Viscosity | formation of silica-oxygen tetrahedra networks |
| Silica Tetrahedron | the basic building block for all the silicate minerals |
| Silicates | silica tetrahedra combine with positively charged ions or shared electrons. |
| Pyroclastic Materials | result from the forceful eruption of magma into the atmosphere |
| Silicic Magma | 65 to 77% SiO2, more viscous, more trapped gases, explosive eruptions, spread as thick, bulbous domes or ash flows |
| Basaltic Magmas | approx 50% SiO2, higher temp, usually more fluid, gases escape easily, usually extruded quietly from fissures over large areas |
| Intrusive Rock | solidifies deep below the surface |
| Extrusive Rock | solidifies at or very near the surface |
| Mineralogy, composition and texture; texture is indicator of cooling history | How igneous rocks are identified and classified |
| Size | relates to cooling rate, and indicates an intrusive or extrusive origin |
| Igneous Rocks | form from crystallizing from a melt, or by explosive volcanic activity |
| Aphanitic | fine grained, rapid cooling |
| Phaneritic | coarse grained, slow cooling |
| Porphyritic | phenocrysts and groundmass, two-stage cooling history |
| Glassy | no crystal structure |
| Vesicular | gas cavities |
| Pyroclastic | fragments generate by explosive volcanism |
| Bowen's Reaction Series | shows how mafic, intermediate, and felsic magmas could derive from an original parent mafic magma |
| Origin of Magma at Spreading Ridges | melting temp rises with increasing pressure, melting temperature decreases when water is present |
| Subduction Zones and the Origin of Magma | partial melting of a mafic crust results in intermediate and felsic magmas |
| Crystal Settling, Magma Mixing and Assimilation | processes resulting in chemical changes in magma |
| Comp of Igneous Rocks | felsic, intermediate, mafic classifications |
| Intrusive Igneous Rock bodies | formed when magma cools beneath the surface and is then uplifted and exposed; classified by shape |
| Batholiths | coarsely crystalline texture, phaneritic, very large rock bodies |
| Dikes | long, narrow tabular rock bodies, location often controlled by fractures in surrounding rocks, cuts across other rock layers, discordant |
| Sills | flat, narrow tubular rock bodies, intrude btwn layers of rock, concordant |
