Geology Rocks and Processes

** few pointers to remember**

• Pyroxene = Augite
• Amphibole = Hornblende
• Olivine = green
• Olivine and Pyroxene = Peridotite
• measurement of silicity = 66 52 45

• Ultramafic ---> pyroxene and olivine

• 
• Mafic ---> pyroxene and K. feldspar

• Silic/ intermediate ---> Quartz, K.feldspar, Plagioclase, Mica, Amphibole
  • Silicic = more Quartz (more viscous)
  • Intermediate = less Quartz (more of the other minerals)
• 

Silicic -------------------------------------------------------------------------------> Ultramafic

                           Increasing darkness, density, Ca, Fe, Mg

                 Decreasing viscosity, Si, Na, K

• Silicic = continental
• Intermediate = Island arc
• Mafic = oceanic
• Ultramafic = Mantle

fractional crystalisation = Soup of magma (all types of rock silicic --> ultrmafic)

                                        = makic minerals for crystals (high temperatures)

                                        = crystals fall to bottom (less dense)

                                        = leaves soup of magma more and more silic

Stoping  = magma rising through lines of weakness

Fissure =  flood of basalt = spills out (very mafic = pressure to get to the top - as can flow)

Batholith ----> PLUTONIC ----> Intrusive

Dykes and Sills ----> HYPABYSSAL ----> Intrusive

Volcanoes -----> VOLCANIC ----> Extrusive

• Dykes = discordent
• 
• Sills =  concordent

• AA lava = thick and blocky
• Pahoehoe = smooth ropey surface

• Ash (< 2mm)
•  
• Lapilli (2-64mm)
• Bombs and blocks (>64)
  • bombs = ejected as liquid but solidify
  • blocks = always solid
    •  
      •  
        • bombs + blocks = agglomerates
        • 
• gases ----> nueree aurdents

• pyroclastic FLOW = on the ground
• Pyroclastic FALL = in the air